Sperm pelotons; article in Nature

[Hugh Trenchard]

On February 12, Roger Critchlow posted a reference to "sperm pelotons",
which inspired me to read the Nature article and to think a bit about how
principles of peloton interactions could be applied to sperm aggregations.
I've outlined some thoughts below.



__________________________________________

DRAFT



Applications of a peloton model to sperm aggregration dynamics

An analysis of article: Fisher, H., Hoekstra, H. (2010) Competition drives
cooperation among closely related sperm of deer mice. Nature. Vol. 463, 11
Feb 801-803

Hugh Trenchard


Abstract

The Nature article by Fisher and Hoekstra suggests that a mechanism exists
among the sperm of certain species of mice to identify genetic relatives.
The identification mechanism itself is not apparent and, based upon
observations of analogous processes in bicycle pelotons, an alternative
hypothesis is suggested.  There are similarities between bicycle pelotons
and sperm aggregations: they are both competitive dynamical systems, and
there are energy savings mechanisms by which agents couple and facilitate
self-organized aggregate formations.  A model for the division of a peloton
at critical output levels is shown and suggested as analogous to certain,
but not all, sperm aggregations, and a model for the relative energy
consumption of coupled and non-coupled aggregates is shown, which suggests
how sub-aggregates may form that are composed of agents within a narrowed
fitness range, and also why the strongest individual agents may not always
reach the target objective first.  This suggests that no mechanism is
required for the identification of genetic relatives, but that sorting
occurs according to a self-organized metabolic process whereby sperm with
close fitness levels will aggregate.  Sorting among sperm is hypothesized to
occur at a critical output threshold, and is more likely to occur among
promiscuous species than monogamous species because sperm velocity of
monogamous species may not be high enough to reach the critical sorting
threshold.  Genetically related sperm are more likely to have closer average
fitness levels, and so will naturally sort into groups composed of
predominantly related sperm. Thus proposed is an alternative framework by
which to analyze the data.
_______________________





Introduction
            Fisher and Hoekstra (2010) provide evidence that supports the
hypothesis that sperm identify related sperm, aggregate and cooperate with
them and, through increased velocity when travelling in aggregations,
provide an advantage to genetically related sperm in advancing one of their
kind to impregnate the egg. The authors report a species of mouse whose
sperm exhibits "the ability to recognize sperm based on genetic relatedness
and preferentially cooperate with the most closely related sperm." The
question was raised: "how do sperm identify their brothers?" (FRIAM, 2010).
The question reveals a problem in Fisher's and Hoekstra's analysis, and a
clear mechanism for this identification process does not appear to be
suggested in their article.

Observations of peloton dynamics allow an alternative explanation to the
cooperative aggregates that Fisher and Hoekstra (2010) have observed.  Here
presented, instead, is the hypothesis that any aggregation among genetically
related sperm is coincidental to what is better explained by aggregates that
form due to coupling among groups of sperm as a result of an energy savings
effect that occurs when sperm travel closely together, an effect that is
similar to drafting in a bicycle peloton. This is a self-organized process
and, as such, no mechanism is required for sperm to identify genetically
related sperm to adjust their positions to be near each other.  This process
includes a sorting of individual sperm into groups with proportionately high
numbers of sperm whose swimming fitness is closest to their own.
Genetically related sperm are more likely to have similar swimming fitness
levels than are unrelated sperm.  Hence grouping is based upon swimming
fitness and not genetic relatedness, which also partially explains why
aggregates are not entirely homogenous according to relatedness: genetically
unrelated sperm with fitness levels near others, who may be related, will
group with them.

For simplicity, here this self-organized energetic process is referred to as
drafting, although for sperm the energy savings mechanism is a hydrodynamic
one (Lauga and Powers, 2009; Woolley et al, 2009).  Similarly, the
interactive dynamic between sperm that allows for this energy savings to
occur is referred to as coupling.  Coupling of this nature has been
described as a synchronization of flagellar motion and optimal positioning
of sperm-heads for friction reduction and increased sperm velocities when
travelling in coupled formations as opposed to individually (Woolley, et al,
2009). Woolley et al (2009) describe the mechanism for coupling in bull
sperm as follows:

The subject of the present study, the flagellar synchronisations, resulted
from chance contacts between individual spermatozoa. These events will be
called 'conjunctions'. In a few instances, the two spermatozoa separated
again after a period of conjunction and they resumed the swimming speeds and
beat frequencies that they had shown before the conjunction.



    Woolley et al. (2009) go on to show distinct increases in mutual speeds
when coupled (i.e. in conjunction states).  Their article does not, however,
appear to discuss overall average savings in energy as sperm accelerate and
decelerate while alternating between conjunctive and separated states
between different sets of coupled sperm, nor do they appear to discuss the
durations of conjunctions/separations, which would provide clues as to
relative differences in inherent fitness and whether sperm aggregations form
with sperm whose range of fitness is relatively narrow.  Here it is
hypothesized that this is, however, what does in fact occur:  this narrowed
fitness range among sperm sub-aggregates due to sorting is more likely to be
the mechanism underlying the genetically related sperm aggregations in the
Fisher and Hoekstra (2010) findings.

The Woolley et al (2009) article suggests that, similarly to cyclists who
save energy by coupling in a peloton, it is unnecessary for sperm to be of
equal physical fitness to travel at the same (mutually increased) speed:  to
travel at equal velocity while being of unequal fitness is facilitated by a
coupled energy savings mechanism.  Similarly, Riedel et al (2005), and Lauga
and Powers (2009), for example, appear to support the notion that there is
in fact some form of energy savings occurring among sperm aggregates.





The peloton sorting model

In bicycle pelotons, drafting allows riders within a range of output
capacities to sustain the same speed: weaker riders drafting can maintain
the same speed as stronger riders ahead according to the equation

                        PDR = (Wa-Wb/Wa) / D*100

¡  Wa is maximum sustainable power (watts) of cyclist A at any given moment

¡  Wb is maximum sustainable power of cyclist B at any given moment

¡  D/100  is the percent energy savings at the speed travelled



This is referred to as the Peloton Divergence Ratio (PDR) (Trenchard, 2009;
2005). Cyclists save energy by drafting at approximately 1% per mile an hour
(Hagberg and McCole, 1990).  So, if for example, cyclists are traveling at
25 mph, they save approximately 25% energy by drafting riders ahead.
Extending the illustration, if stronger cyclist A has a maximum sustainable
output at 400w at 25mph, and cyclist B has a maximum sustainable output of
300w, cyclist B could not sustain the same speed as cyclist A if they were
travelling individually and without drafting.  Thus where cyclist B has only
75% the output capacity of cyclist A, PDR = (400-300/400) /D*100; PDR=1.  As
long as PDR is <1, cyclists can maintain the same speed.  If PDR>1, cyclists
will not be able to maintain the same speed and will diverge, or decouple.
So, at a speed of 25mph, all cyclists within a range of 25% output capacity
can travel at the same speed.

Here it is suggested that PDR applies to certain types of sperm
aggregations, though not necessarily to all types, as there are several
different types of sperm morphology (Immler, et al. 2007), and their
respective energy savings mechanisms therefore cannot be assumed to be the
same.  In fact, PDR does not appear to apply to the Woolley et al (2009)
bull sperm observations, although it may to the Riedel (2005) observations,
the Moore et al. (2002) and Immler (2007) observations of "train"
aggregations, which in pelotons occur during a distinctive phase of energy
output when all riders are riding at or near maximum sustainable speeds, or
when riders are at or near PDR=1.   The phase is unstable and small
increases in speed or disturbances in rider positioning can put riders at
PDR>1 and precedes peloton separations and the formation of sub-pelotons.

When cyclists in a peloton approach PDR=1,  a sorting process occurs whereby
sub-pelotons form that are composed of cyclists within a smaller range of
inherent fitness levels; i.e. each cyclist in the group has an inherent
fitness level (max sustainable output) that is closer to the average of the
sub-group than it is to the larger aggregate.  When peloton divisions occur
at points of instability (PDR >1) and cyclists in a competitive situation
exert maximal efforts to remain among the composition of the group ahead,
but are unable to do so, it is self-evident that the average fitness of the
group behind is less than that ahead, and that each of the groups contain
cyclists of closer average fitness than when among the undivided aggregate.

The range of fitness within each sub-group is also effectively narrowed
further by the drafting process, as evidenced by the fact that sub-pelotons
in a mass-start bicycle race finish a race with nearly identical finishing
times (eg. see data in Trenchard, H., Mayer-Kress, G., 2005). This would not
be self-evident or a reasonable conclusion if the groups were not all
proceeding at maximum sustainable outputs, but had divided for
non-competitive reasons.

This conclusion, however, does not preclude the possibility that some
cyclists with fitness levels which could sustain them in faster groups do
end up in slower groups (i.e. fitness levels that are substantially above
the average of the group), and so there may be a small proportion of
cyclists with fitness levels that overlap the ranges of different groups, as
would there be among sperm sub-aggregates.

The sorting process and formation of aggregates with close average fitness
is well illustrated by imagining a peloton composed of 75 cyclists with a
broad range of abilities: 25 cyclists are professional level and can sustain
speeds of 50k an hour on the flat without drafting, 25 cyclists are medium
amateur level and can sustain speeds of 30km on the flat without drafting;
25cyclists are kids who can sustain speeds of 15km per hour on the flat
without drafting.  If they all start together, the peloton is 75 strong up
to approximately 20km/h (because the kids can draft, they can go faster than
they could without drafting); at 21 km/h, the peloton sorts into two groups:
25 kids, and 50 medium and pro cyclists.  The group of 50 accelerates, and
when they travel at approximately 36km/h the peloton divides again.  It
divides at 36km/h and not 30km/h because the medium-level riders can draft
up to speeds approximately 20 percent faster than they could achieve on
their own without drafting.  When speeds of 36km/h are sustained, eventually
all the medium-level cyclists will be separated from the professional
cyclists, and most, if not all, will end up together in a group.  At this
point the original peloton has divided into three groups containing riders
with fitness levels near to the average of the group.  In an actual
competition and peloton that is composed of all professional riders, the
sorting process is more subtle because average fitness of all the cyclists
is very close from the outset, but the effect is fundamentally the same.



Applying the peloton model to sperm aggregations and the Fisher and Hoekstra
findings

Here it is hypothesized that a similar sorting dynamic occurs in sperm
aggregations and may provide a clue as to the composition of the
sub-aggregates and the proportional representation of conspecific and
heterospecific sperm in any given aggregate, as identified by Fisher and
Hoekstra (2010).  Thus if the sperm of two males, say heterospecific in the
first example the authors provide, is mixed into an initial single
aggregate, the aggregate will begin to divide according to PDR as the sperm
accelerate. Sorting occurs as weaker sperm end up being "dropped" into
trailing sub-aggregates, as in the peloton illustration above.  Thus, if a
set of sperm from an individual conspecific male are, as a group, fitter
than those of the heterospecific competitor, there will be a self-organized
tendency for sperm of close physical fitness to group together.  Some
individual sperm from other groups, however, will be capable of sustaining
the speed of fitter sperm if they group with fitter sperm, as long as they
are at PDR<1  The proposition is thus that genetically related sperm are
naturally closer in physical fitness and therefore will tend to aggregate
together through self-organized coupling dynamics, as presented here.

The composition of sperm aggregates is thus determined by individual sperm
fitness levels and the energy savings due to drafting at the velocity
travelled.  Divergences in the aggregates occur at critical individual
output/speed levels.  This is particularly so in the case of the promiscuous
species, P. maniculatus, and here it is assumed that sperm in a competitive
situation naturally swim at or near maximum sustainable speeds.  This is a
reasonable assumption in a competitive situation, in which all sperm are
seeking to reach the egg first.

However, as indicated in the Fisher and Hoekstra article, in the case of P.
polionatus, the monogamous species, sperm may not travel at or near maximum
sustainable speeds, which suggests that the same degree of sorting does not
occur as among their faster swimming P. maniculatus counterparts.  This
provides an explanation why P. polionatus sperm tend to mix
indiscriminately, as the authors describe (see Table 1); i.e. the sperm have
adapted to swimming at less than maximum speeds as an intrinsic
characteristic of monogamous species, and the sorting of sperm into groups
with nearly equal fitness does not occur because the critical output
threshold is not reached for this to happen.

Table 1 summarizes findings presented in the Fisher and Hoekstra article and
provides an alternative peloton model explanation.  Fisher and Hoekstra show
results for three experiments involving different combinations of mouse
species sperm mixes.  Table 1 summarizes both the results of the Fisher and
Hoekstra study, and the alternative peloton model explanation:


     Test
     Result
     Peloton model explanation

      1
     Sperm from one heterospecific (P. polionotus) male and one conspecific
(P. maniculatus) male are mixed in vivo assay
     "found that overall groups were composed of significantly more
conspecific sperm than expected at random"
     Sperm from each of the conspecific males exhibit closer physiological
fitness than as between heterospecifics; i.e. conspecific males have average
fitness close to each other, as do rival heterospecifics to each other .
Some sperm for each sets, however, exhibit close physiological fitness
levels, and these represent the proportion of the aggregates that are not
from conspecific males. There are also percentages of each of
heterospecifics and conspecifics whose fitnesses are such that they are
capable of travelling with groups, but which are "trapped" in the slower
travelling groups.

      2
     Sperm from two unrelated male P. maniculatus, a promiscuous species,
are mixed
     "sperm group significantly more often with sperm of the same male than
expected at random"
     The explanation above applies to the related conspecific maniculatus
males

      3
     Sperm from two unrelated conspecific males of P. polionatus, a
monogamous species, are mixed
     "aggregations form indiscriminately in assays"
     The speed at which these sperm aggregations travel is relevant.  It may
be that the sperm of monogamous species travel slower (due to decreased
competition) than the critical speed at which self-organized sorting occurs.

      4
     Sperm from related P. maniculatus was mixed
     "found a greater proportion of sperm from the same male grouped
together than was expected at random."
     The explanation in cases 1 and 2 above applies to the related
conspecific maniculatus males


Table 1

In cases 1,2 and 4, the sorting process described in the foregoing provides
a reasonable alternative explanation to the formation of sperm aggregrations
with close average fitness, and the proposition that it is likely that sperm
of one male have closer average fitness than another male, whether it is
related or not.  Some proportion of the two sets of sperm will mix, but at
the critical threshold when sorting occurs, sperm with nearest average
fitness will aggregate.

In case 3, the lower vitality of monogamous sperm, as the authors' finding
indicate, and the smaller testes of P. polionatus suggests that sperm
swimming speeds are slower and/or do not proceed at near maximal output
levels.  The slower sperm speeds of monogamous species is supported by other
finding (Nascimento, 2008; Fitzpatrick et al. 2009), although it is not
clear whether sperm are simply slower with a lesser maximum output capacity,
or whether they are in fact capable of swimming faster, but simply do not.
If the peloton model holds, then the inference is that the sperm of
monogamous species are capable of swimming faster but do not do so and, as a
result, are less likely to reach the critical output threshold by which they
will sort into sub-aggregates that contain sperm of near equal fitness
levels.  These relative speeds and output levels should be investigated and
confirmed.



Conclusion

The analysis here presents an alternative hypothesis for the findings
presented in the Fisher and Hoekstra article. Based upon analogous behavior
observed in bicycle-pelotons, it provides an analytical and experimental
framework by which existing data could be re-analyzed or further experiments
conducted to test for the observations and principles outlined.

References



FRIAM email listserv Feb 12, 2010, R. Critchlow. Vertical axis windmills and
sperm pelotons.



Hagberg, J. and McCole, S. 1990.  The effect of drafting and aerodynamic
equipment on energy expenditure during cycling. Cycling Science 2:20.

Immler, S., Harry D.M. Moore, H., William G. Breed, W., Birkhead, R. (2007).
By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent
Sperm, PLoS ONE. 2(1): e170.

Published online 2007 January 24.



Lauga, E., Powers, T. The hydrodynamics of swimming microorganisms.  Rep.
Prog. Phys. 72 (2009) 096601


Moore, H., Dvorakova, K., Jenkins, N. Breed., W. (2002). Exceptional sperm
cooperation in the wood mouse. Nature 418, 174-177


Nascimento JM, et al.(2008) The use of optical tweezers to study sperm
competition and motility in primates. J R Soc Inter 5:297-302. Published
online 2007 July 24. doi: 10.1098/rsif.2007.1118.

Fitzpatrick, J., Montgomerie, R., Desjardins, J., Kelly, S., Kolm, N.,
Balshine, S. Female promiscuity promotes the evolution of faster sperm in
cichlid fishes PNAS January 27, 2009 vol. 106 no. 4 1128-1132


Riedel, et al. 2005. A Self-Organized Vortex Array of Hydrodynamically
Entrained Sperm Cells

Science 8 July 2005: 300-303

Trenchard, H., Mayer-Kress, G.  (2005) Self-organized oscillator coupling
and synchronization in bicycle pelotons during mass-start bicycle racing.
Intl Conference on Control and Synchronization of Dynamical Systems. Oct 4-7
Leon, Gto. Mexico.



Trenchard, H.  (2009).  Self-organized coupling dynamics and phase
transitions in bicycle pelotons.  AAAI Fall Symposium, Arlington VA.
Technical Report Series FS-09-03.



Woolley, D., Crockett, R., Grook. W., Revell, S. (2009). A study of
synchronisation between the flagella of bull spermatozoa, with related
Observations. The Journal of Experimental Biology 212, 2215-2223



Yang, Y., Elgeti, J, Gompper, G. (2008) Cooperation of sperm in two
dimensions: synchronization, attraction, aggregation through dynamic
interactions. Phys Rev. E. 061903





Appendix A

Further development of the peloton/sperm aggregation model

Note that PDR is a useful model if an energy savings mechanism exists
whereby one of two coupled sperm benefits from the energy savings mechanism,
while the other does not.  This may be the mechanism in the mouse species
described in the Moore (2002) and Immler (2007) articles, as indicated by
the "train" formation, which is similar to "single paceline" peloton
formations when cyclists are aligned near or at PDR=1 to each other
(Trenchard, 2009; 2005).

 There do appear, however, to be other energy savings mechanisms in sperm
aggregates, such as for example the conjunction and synchronized dynamic of
bull sperm (Woolley et al, 2009).  In a sperm conjunction (Woolley et al,
2009), the PDR equation does not strictly apply and must be adjusted because
the stronger sperm also appears to benefit from the coupled formation, which
does not occur to any significant degree between coupled cyclists; i.e. in a
peloton the front riding cyclist does not receive any reduction in output
from the rider behind, while the rider behind benefits substantially by
drafting; for bull sperm, it appears that both coupled sperm benefit by
increased velocity.

This leads to a further hypothesis that the stronger sperm increases speed
with some reduction in metabolic cost, while the weaker sperm increases
speed with little or no change in metabolic cost, although they both travel
faster than they would individually.  Thus it is the stronger sperm that
benefits by energy savings, while the weaker sperm benefits by increased
speed, but with no savings in energy.  There is an implication that the
stronger sperm will always be able to advance to the front of the sperm
aggregation faster than weaker sperm.  However, this is not necessarily so,
as it depends on the relative durations of coupling and separations.  That
is to say, a weaker sperm could advance farther and faster than a stronger
sperm if it spends sufficiently more time coupled than a stronger sperm
which may spend relatively more time isolated.  Thus the faster sperm are
not necessarily those that are stronger, but those whose proportion of total
coupling time exceeds the percent differences in their relative fitness
levels.

The following model is descriptive for coupled organisms that may alternate
durations of time spent coupled with time spent non-coupled, and which
mutually benefit from coupling because it accounts for the proportions of
total time spent both saving energy in coupled positions and not saving
energy in non-coupled positions.  It is a simplified model because there are
other factors that affect total output than time spent in energy-saving
positions (coupled) and positions where there is no energy savings.
However, it provides insight into the energetic dynamics of coupled agents
of varying degrees of fitness and why they do not necessarily achieve
positions based on inherent fitness.



TO = Wa-(Wa*%E) * T)  /  Wb-(Wb*%E) * T)



·         Where TO is ratio of total output of two agents in coupled
positions (not necessarily with each other) with identical objective (e.g.
to win a race or impregnate an egg); here, sperm or cyclist; in the case of
sperm, millijoules; for cyclists, calories

·         T is total time spent in coupled positions and travelling at
mutually faster velocities than achievable in isolation

·         %E is percent energy savings in coupled formation

·         Wa is the maximum sustainable power output; picoNewtons for sperm,
watts for cyclists of stronger agent A (cyclist or sperm) at a given moment
, assuming that in a competitive situation, agents are travelling as fast as
their metabolisms will allow.

·         Wb is the maximum sustainable power output at a given moment of
weaker agent B, again assuming that in a competitive situation, agents
travel as fast as metabolisms will allow.



For example (quantities and units for illustration only): if stronger sperm
A has max sustainable output of 50pN, and B has max sustainable output of
45pN, and A saves an average of 10% output when coupled and spends a total
of 10 minutes coupled, total output for A is 50-5*10, or 450mj, while the
weaker sperm saves no energy when coupled, but spends 11 minutes in coupled
positions, we have 45-0*11, 495; and 450/495 = 0.91. Thus where this ratio
is <1, the weaker sperm potentially can be ahead of the stronger sperm over
the duration of the coupling interactions.  Thus this ratio indicates why it
is not necessarily the case that stronger sperm will impregnate the egg.







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[Nick Thompson]

This is fun to think about.  Hopefully, REC will help me:

Is there a paradox here.  let it be the case that sperm sort themselves by
fitness;  let it further be the case that sperm in peletons have an
advantage over sperm that dont.  Isnt it now the case that sperm are no
longer sorting themselves by fitness?

Ok, forget that:  so let be the case that "fitness" is not defined by
fertization probability, but more in the sense of "physical fitness".  Some
of the sperm go to the gym, and some don't.  Or some are more muscular than
others.  So let it be the case that sperm sort themselves by swimming
speed. The more muscular sperm swim side by side and the less muscular
sperm swim side by side.  But wait a minute, other things being equal
wouldnt everybody bet the peleton effect?  Ok,  forget THAT, too.  

All these models assume that everbody starts from the same starting point,
right?  Are they  jostling at the starting gate in the prostate as they are
mixed with the seminal fluid.  Is there an advantage to being in the first
pulsation?  So f orth.  Wouldnt these factors overwhelm the peleton effect?

And, what about the kamakaze sperm, that stick pumps in the spokes of
unrelated sperm as in that unforgettable scene in Breaking Away.  

Ok.  Sorry.  Forget the whole thing.  I do so like metaphors.

Nick  

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: The Friday Morning Applied Complexity Coffee Group <[hidden email]>
> Date: 3/26/2010 8:38:22 PM
> Subject: [FRIAM]  Sperm pelotons; article in Nature
>
> On February 12, Roger Critchlow posted a reference to "sperm pelotons",
> which inspired me to read the Nature article and to think a bit about how
> principles of peloton interactions could be applied to sperm
aggregations.

> I've outlined some thoughts below.
>
>
>
> __________________________________________
>
> DRAFT
>
>
>
> Applications of a peloton model to sperm aggregration dynamics
>
> An analysis of article: Fisher, H., Hoekstra, H. (2010) Competition

drives
> cooperation among closely related sperm of deer mice. Nature. Vol. 463,

11
> Feb 801-803
>
> Hugh Trenchard
>
>
> Abstract
>
> The Nature article by Fisher and Hoekstra suggests that a mechanism
exists
> among the sperm of certain species of mice to identify genetic relatives.
> The identification mechanism itself is not apparent and, based upon
> observations of analogous processes in bicycle pelotons, an alternative
> hypothesis is suggested.  There are similarities between bicycle pelotons
> and sperm aggregations: they are both competitive dynamical systems, and
> there are energy savings mechanisms by which agents couple and facilitate
> self-organized aggregate formations.  A model for the division of a
peloton
> at critical output levels is shown and suggested as analogous to certain,
> but not all, sperm aggregations, and a model for the relative energy
> consumption of coupled and non-coupled aggregates is shown, which
suggests
> how sub-aggregates may form that are composed of agents within a narrowed
> fitness range, and also why the strongest individual agents may not
always
> reach the target objective first.  This suggests that no mechanism is
> required for the identification of genetic relatives, but that sorting
> occurs according to a self-organized metabolic process whereby sperm with
> close fitness levels will aggregate.  Sorting among sperm is hypothesized
to
> occur at a critical output threshold, and is more likely to occur among
> promiscuous species than monogamous species because sperm velocity of
> monogamous species may not be high enough to reach the critical sorting
> threshold.  Genetically related sperm are more likely to have closer
average

> fitness levels, and so will naturally sort into groups composed of
> predominantly related sperm. Thus proposed is an alternative framework by
> which to analyze the data.
> _______________________
>
>
>
>
>
> Introduction
>             Fisher and Hoekstra (2010) provide evidence that supports the
> hypothesis that sperm identify related sperm, aggregate and cooperate

with
> them and, through increased velocity when travelling in aggregations,
> provide an advantage to genetically related sperm in advancing one of

their
> kind to impregnate the egg. The authors report a species of mouse whose
> sperm exhibits "the ability to recognize sperm based on genetic
relatedness
> and preferentially cooperate with the most closely related sperm." The
> question was raised: "how do sperm identify their brothers?" (FRIAM,
2010).
> The question reveals a problem in Fisher's and Hoekstra's analysis, and a
> clear mechanism for this identification process does not appear to be
> suggested in their article.
>
> Observations of peloton dynamics allow an alternative explanation to the
> cooperative aggregates that Fisher and Hoekstra (2010) have observed.
Here
> presented, instead, is the hypothesis that any aggregation among
genetically
> related sperm is coincidental to what is better explained by aggregates
that
> form due to coupling among groups of sperm as a result of an energy
savings
> effect that occurs when sperm travel closely together, an effect that is
> similar to drafting in a bicycle peloton. This is a self-organized
process
> and, as such, no mechanism is required for sperm to identify genetically
> related sperm to adjust their positions to be near each other.  This
process
> includes a sorting of individual sperm into groups with proportionately
high
> numbers of sperm whose swimming fitness is closest to their own.
> Genetically related sperm are more likely to have similar swimming
fitness
> levels than are unrelated sperm.  Hence grouping is based upon swimming
> fitness and not genetic relatedness, which also partially explains why
> aggregates are not entirely homogenous according to relatedness:
genetically
> unrelated sperm with fitness levels near others, who may be related, will
> group with them.
>
> For simplicity, here this self-organized energetic process is referred to
as
> drafting, although for sperm the energy savings mechanism is a
hydrodynamic
> one (Lauga and Powers, 2009; Woolley et al, 2009).  Similarly, the
> interactive dynamic between sperm that allows for this energy savings to
> occur is referred to as coupling.  Coupling of this nature has been
> described as a synchronization of flagellar motion and optimal
positioning
> of sperm-heads for friction reduction and increased sperm velocities when
> travelling in coupled formations as opposed to individually (Woolley, et
al,
> 2009). Woolley et al (2009) describe the mechanism for coupling in bull
> sperm as follows:
>
> The subject of the present study, the flagellar synchronisations,
resulted
> from chance contacts between individual spermatozoa. These events will be
> called 'conjunctions'. In a few instances, the two spermatozoa separated
> again after a period of conjunction and they resumed the swimming speeds
and
> beat frequencies that they had shown before the conjunction.
>
>
>
>     Woolley et al. (2009) go on to show distinct increases in mutual
speeds
> when coupled (i.e. in conjunction states).  Their article does not,
however,
> appear to discuss overall average savings in energy as sperm accelerate
and
> decelerate while alternating between conjunctive and separated states
> between different sets of coupled sperm, nor do they appear to discuss
the
> durations of conjunctions/separations, which would provide clues as to
> relative differences in inherent fitness and whether sperm aggregations
form
> with sperm whose range of fitness is relatively narrow.  Here it is
> hypothesized that this is, however, what does in fact occur:  this
narrowed
> fitness range among sperm sub-aggregates due to sorting is more likely to
be
> the mechanism underlying the genetically related sperm aggregations in
the
> Fisher and Hoekstra (2010) findings.
>
> The Woolley et al (2009) article suggests that, similarly to cyclists who
> save energy by coupling in a peloton, it is unnecessary for sperm to be
of
> equal physical fitness to travel at the same (mutually increased) speed:
to
> travel at equal velocity while being of unequal fitness is facilitated by
a
> coupled energy savings mechanism.  Similarly, Riedel et al (2005), and
Lauga
> and Powers (2009), for example, appear to support the notion that there
is

> in fact some form of energy savings occurring among sperm aggregates.
>
>
>
>
>
> The peloton sorting model
>
> In bicycle pelotons, drafting allows riders within a range of output
> capacities to sustain the same speed: weaker riders drafting can maintain
> the same speed as stronger riders ahead according to the equation
>
>                         PDR = (Wa-Wb/Wa) / D*100
>
> ¡  Wa is maximum sustainable power (watts) of cyclist A at any given

moment
>
> ¡  Wb is maximum sustainable power of cyclist B at any given moment
>
> ¡  D/100  is the percent energy savings at the speed travelled
>
>
>
> This is referred to as the Peloton Divergence Ratio (PDR) (Trenchard,

2009;
> 2005). Cyclists save energy by drafting at approximately 1% per mile an
hour
> (Hagberg and McCole, 1990).  So, if for example, cyclists are traveling
at
> 25 mph, they save approximately 25% energy by drafting riders ahead.
> Extending the illustration, if stronger cyclist A has a maximum
sustainable
> output at 400w at 25mph, and cyclist B has a maximum sustainable output
of
> 300w, cyclist B could not sustain the same speed as cyclist A if they
were
> travelling individually and without drafting.  Thus where cyclist B has
only
> 75% the output capacity of cyclist A, PDR = (400-300/400) /D*100; PDR=1.
As
> long as PDR is <1, cyclists can maintain the same speed.  If PDR>1,
cyclists
> will not be able to maintain the same speed and will diverge, or
decouple.
> So, at a speed of 25mph, all cyclists within a range of 25% output
capacity
> can travel at the same speed.
>
> Here it is suggested that PDR applies to certain types of sperm
> aggregations, though not necessarily to all types, as there are several
> different types of sperm morphology (Immler, et al. 2007), and their
> respective energy savings mechanisms therefore cannot be assumed to be
the
> same.  In fact, PDR does not appear to apply to the Woolley et al (2009)
> bull sperm observations, although it may to the Riedel (2005)
observations,
> the Moore et al. (2002) and Immler (2007) observations of "train"
> aggregations, which in pelotons occur during a distinctive phase of
energy
> output when all riders are riding at or near maximum sustainable speeds,
or
> when riders are at or near PDR=1.   The phase is unstable and small
> increases in speed or disturbances in rider positioning can put riders at
> PDR>1 and precedes peloton separations and the formation of sub-pelotons.
>
> When cyclists in a peloton approach PDR=1,  a sorting process occurs
whereby
> sub-pelotons form that are composed of cyclists within a smaller range of
> inherent fitness levels; i.e. each cyclist in the group has an inherent
> fitness level (max sustainable output) that is closer to the average of
the
> sub-group than it is to the larger aggregate.  When peloton divisions
occur
> at points of instability (PDR >1) and cyclists in a competitive situation
> exert maximal efforts to remain among the composition of the group ahead,
> but are unable to do so, it is self-evident that the average fitness of
the
> group behind is less than that ahead, and that each of the groups contain
> cyclists of closer average fitness than when among the undivided
aggregate.
>
> The range of fitness within each sub-group is also effectively narrowed
> further by the drafting process, as evidenced by the fact that
sub-pelotons
> in a mass-start bicycle race finish a race with nearly identical
finishing
> times (eg. see data in Trenchard, H., Mayer-Kress, G., 2005). This would
not
> be self-evident or a reasonable conclusion if the groups were not all
> proceeding at maximum sustainable outputs, but had divided for
> non-competitive reasons.
>
> This conclusion, however, does not preclude the possibility that some
> cyclists with fitness levels which could sustain them in faster groups do
> end up in slower groups (i.e. fitness levels that are substantially above
> the average of the group), and so there may be a small proportion of
> cyclists with fitness levels that overlap the ranges of different groups,
as
> would there be among sperm sub-aggregates.
>
> The sorting process and formation of aggregates with close average
fitness
> is well illustrated by imagining a peloton composed of 75 cyclists with a
> broad range of abilities: 25 cyclists are professional level and can
sustain
> speeds of 50k an hour on the flat without drafting, 25 cyclists are
medium
> amateur level and can sustain speeds of 30km on the flat without
drafting;
> 25cyclists are kids who can sustain speeds of 15km per hour on the flat
> without drafting.  If they all start together, the peloton is 75 strong
up
> to approximately 20km/h (because the kids can draft, they can go faster
than
> they could without drafting); at 21 km/h, the peloton sorts into two
groups:
> 25 kids, and 50 medium and pro cyclists.  The group of 50 accelerates,
and
> when they travel at approximately 36km/h the peloton divides again.  It
> divides at 36km/h and not 30km/h because the medium-level riders can
draft
> up to speeds approximately 20 percent faster than they could achieve on
> their own without drafting.  When speeds of 36km/h are sustained,
eventually
> all the medium-level cyclists will be separated from the professional
> cyclists, and most, if not all, will end up together in a group.  At this
> point the original peloton has divided into three groups containing
riders
> with fitness levels near to the average of the group.  In an actual
> competition and peloton that is composed of all professional riders, the
> sorting process is more subtle because average fitness of all the
cyclists
> is very close from the outset, but the effect is fundamentally the same.
>
>
>
> Applying the peloton model to sperm aggregations and the Fisher and
Hoekstra
> findings
>
> Here it is hypothesized that a similar sorting dynamic occurs in sperm
> aggregations and may provide a clue as to the composition of the
> sub-aggregates and the proportional representation of conspecific and
> heterospecific sperm in any given aggregate, as identified by Fisher and
> Hoekstra (2010).  Thus if the sperm of two males, say heterospecific in
the
> first example the authors provide, is mixed into an initial single
> aggregate, the aggregate will begin to divide according to PDR as the
sperm
> accelerate. Sorting occurs as weaker sperm end up being "dropped" into
> trailing sub-aggregates, as in the peloton illustration above.  Thus, if
a
> set of sperm from an individual conspecific male are, as a group, fitter
> than those of the heterospecific competitor, there will be a
self-organized
> tendency for sperm of close physical fitness to group together.  Some
> individual sperm from other groups, however, will be capable of
sustaining
> the speed of fitter sperm if they group with fitter sperm, as long as
they
> are at PDR<1  The proposition is thus that genetically related sperm are
> naturally closer in physical fitness and therefore will tend to aggregate
> together through self-organized coupling dynamics, as presented here.
>
> The composition of sperm aggregates is thus determined by individual
sperm
> fitness levels and the energy savings due to drafting at the velocity
> travelled.  Divergences in the aggregates occur at critical individual
> output/speed levels.  This is particularly so in the case of the
promiscuous
> species, P. maniculatus, and here it is assumed that sperm in a
competitive
> situation naturally swim at or near maximum sustainable speeds.  This is
a
> reasonable assumption in a competitive situation, in which all sperm are
> seeking to reach the egg first.
>
> However, as indicated in the Fisher and Hoekstra article, in the case of
P.
> polionatus, the monogamous species, sperm may not travel at or near
maximum
> sustainable speeds, which suggests that the same degree of sorting does
not
> occur as among their faster swimming P. maniculatus counterparts.  This
> provides an explanation why P. polionatus sperm tend to mix
> indiscriminately, as the authors describe (see Table 1); i.e. the sperm
have
> adapted to swimming at less than maximum speeds as an intrinsic
> characteristic of monogamous species, and the sorting of sperm into
groups
> with nearly equal fitness does not occur because the critical output
> threshold is not reached for this to happen.
>
> Table 1 summarizes findings presented in the Fisher and Hoekstra article
and
> provides an alternative peloton model explanation.  Fisher and Hoekstra
show
> results for three experiments involving different combinations of mouse
> species sperm mixes.  Table 1 summarizes both the results of the Fisher
and
> Hoekstra study, and the alternative peloton model explanation:
>
>
>      Test
>      Result
>      Peloton model explanation
>
>       1
>      Sperm from one heterospecific (P. polionotus) male and one
conspecific
> (P. maniculatus) male are mixed in vivo assay
>      "found that overall groups were composed of significantly more
> conspecific sperm than expected at random"
>      Sperm from each of the conspecific males exhibit closer
physiological
> fitness than as between heterospecifics; i.e. conspecific males have
average

> fitness close to each other, as do rival heterospecifics to each other .
> Some sperm for each sets, however, exhibit close physiological fitness
> levels, and these represent the proportion of the aggregates that are not
> from conspecific males. There are also percentages of each of
> heterospecifics and conspecifics whose fitnesses are such that they are
> capable of travelling with groups, but which are "trapped" in the slower
> travelling groups.
>
>       2
>      Sperm from two unrelated male P. maniculatus, a promiscuous species,
> are mixed
>      "sperm group significantly more often with sperm of the same male

than
> expected at random"
>      The explanation above applies to the related conspecific maniculatus
> males
>
>       3
>      Sperm from two unrelated conspecific males of P. polionatus, a
> monogamous species, are mixed
>      "aggregations form indiscriminately in assays"
>      The speed at which these sperm aggregations travel is relevant.  It

may
> be that the sperm of monogamous species travel slower (due to decreased
> competition) than the critical speed at which self-organized sorting
occurs.

>
>       4
>      Sperm from related P. maniculatus was mixed
>      "found a greater proportion of sperm from the same male grouped
> together than was expected at random."
>      The explanation in cases 1 and 2 above applies to the related
> conspecific maniculatus males
>
>
> Table 1
>
> In cases 1,2 and 4, the sorting process described in the foregoing

provides
> a reasonable alternative explanation to the formation of sperm

aggregrations
> with close average fitness, and the proposition that it is likely that
sperm
> of one male have closer average fitness than another male, whether it is
> related or not.  Some proportion of the two sets of sperm will mix, but
at
> the critical threshold when sorting occurs, sperm with nearest average
> fitness will aggregate.
>
> In case 3, the lower vitality of monogamous sperm, as the authors'
finding
> indicate, and the smaller testes of P. polionatus suggests that sperm
> swimming speeds are slower and/or do not proceed at near maximal output
> levels.  The slower sperm speeds of monogamous species is supported by
other
> finding (Nascimento, 2008; Fitzpatrick et al. 2009), although it is not
> clear whether sperm are simply slower with a lesser maximum output
capacity,
> or whether they are in fact capable of swimming faster, but simply do
not.
> If the peloton model holds, then the inference is that the sperm of
> monogamous species are capable of swimming faster but do not do so and,
as a
> result, are less likely to reach the critical output threshold by which
they
> will sort into sub-aggregates that contain sperm of near equal fitness
> levels.  These relative speeds and output levels should be investigated
and
> confirmed.
>
>
>
> Conclusion
>
> The analysis here presents an alternative hypothesis for the findings
> presented in the Fisher and Hoekstra article. Based upon analogous
behavior
> observed in bicycle-pelotons, it provides an analytical and experimental
> framework by which existing data could be re-analyzed or further
experiments
> conducted to test for the observations and principles outlined.
>
> References
>
>
>
> FRIAM email listserv Feb 12, 2010, R. Critchlow. Vertical axis windmills
and
> sperm pelotons.
>
>
>
> Hagberg, J. and McCole, S. 1990.  The effect of drafting and aerodynamic
> equipment on energy expenditure during cycling. Cycling Science 2:20.
>
> Immler, S., Harry D.M. Moore, H., William G. Breed, W., Birkhead, R.
(2007).

> By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent
> Sperm, PLoS ONE. 2(1): e170.
>
> Published online 2007 January 24.
>
>
>
> Lauga, E., Powers, T. The hydrodynamics of swimming microorganisms.  Rep.
> Prog. Phys. 72 (2009) 096601
>
>
> Moore, H., Dvorakova, K., Jenkins, N. Breed., W. (2002). Exceptional

sperm

> cooperation in the wood mouse. Nature 418, 174-177
>
>
> Nascimento JM, et al.(2008) The use of optical tweezers to study sperm
> competition and motility in primates. J R Soc Inter 5:297-302. Published
> online 2007 July 24. doi: 10.1098/rsif.2007.1118.
>
> Fitzpatrick, J., Montgomerie, R., Desjardins, J., Kelly, S., Kolm, N.,
> Balshine, S. Female promiscuity promotes the evolution of faster sperm in
> cichlid fishes PNAS January 27, 2009 vol. 106 no. 4 1128-1132
>
>
> Riedel, et al. 2005. A Self-Organized Vortex Array of Hydrodynamically
> Entrained Sperm Cells
>
> Science 8 July 2005: 300-303
>
> Trenchard, H., Mayer-Kress, G.  (2005) Self-organized oscillator coupling
> and synchronization in bicycle pelotons during mass-start bicycle racing.
> Intl Conference on Control and Synchronization of Dynamical Systems. Oct

4-7

> Leon, Gto. Mexico.
>
>
>
> Trenchard, H.  (2009).  Self-organized coupling dynamics and phase
> transitions in bicycle pelotons.  AAAI Fall Symposium, Arlington VA.
> Technical Report Series FS-09-03.
>
>
>
> Woolley, D., Crockett, R., Grook. W., Revell, S. (2009). A study of
> synchronisation between the flagella of bull spermatozoa, with related
> Observations. The Journal of Experimental Biology 212, 2215-2223
>
>
>
> Yang, Y., Elgeti, J, Gompper, G. (2008) Cooperation of sperm in two
> dimensions: synchronization, attraction, aggregation through dynamic
> interactions. Phys Rev. E. 061903
>
>
>
>
>
> Appendix A
>
> Further development of the peloton/sperm aggregation model
>
> Note that PDR is a useful model if an energy savings mechanism exists
> whereby one of two coupled sperm benefits from the energy savings

mechanism,
> while the other does not.  This may be the mechanism in the mouse species
> described in the Moore (2002) and Immler (2007) articles, as indicated by
> the "train" formation, which is similar to "single paceline" peloton
> formations when cyclists are aligned near or at PDR=1 to each other
> (Trenchard, 2009; 2005).
>
>  There do appear, however, to be other energy savings mechanisms in sperm
> aggregates, such as for example the conjunction and synchronized dynamic

of
> bull sperm (Woolley et al, 2009).  In a sperm conjunction (Woolley et al,
> 2009), the PDR equation does not strictly apply and must be adjusted
because
> the stronger sperm also appears to benefit from the coupled formation,
which
> does not occur to any significant degree between coupled cyclists; i.e.
in a
> peloton the front riding cyclist does not receive any reduction in output
> from the rider behind, while the rider behind benefits substantially by
> drafting; for bull sperm, it appears that both coupled sperm benefit by
> increased velocity.
>
> This leads to a further hypothesis that the stronger sperm increases
speed
> with some reduction in metabolic cost, while the weaker sperm increases
> speed with little or no change in metabolic cost, although they both
travel
> faster than they would individually.  Thus it is the stronger sperm that
> benefits by energy savings, while the weaker sperm benefits by increased
> speed, but with no savings in energy.  There is an implication that the
> stronger sperm will always be able to advance to the front of the sperm
> aggregation faster than weaker sperm.  However, this is not necessarily
so,
> as it depends on the relative durations of coupling and separations.
That
> is to say, a weaker sperm could advance farther and faster than a
stronger
> sperm if it spends sufficiently more time coupled than a stronger sperm
> which may spend relatively more time isolated.  Thus the faster sperm are
> not necessarily those that are stronger, but those whose proportion of
total
> coupling time exceeds the percent differences in their relative fitness
> levels.
>
> The following model is descriptive for coupled organisms that may
alternate
> durations of time spent coupled with time spent non-coupled, and which
> mutually benefit from coupling because it accounts for the proportions of
> total time spent both saving energy in coupled positions and not saving
> energy in non-coupled positions.  It is a simplified model because there
are
> other factors that affect total output than time spent in energy-saving
> positions (coupled) and positions where there is no energy savings.
> However, it provides insight into the energetic dynamics of coupled
agents

> of varying degrees of fitness and why they do not necessarily achieve
> positions based on inherent fitness.
>
>
>
> TO = Wa-(Wa*%E) * T)  /  Wb-(Wb*%E) * T)
>
>
>
> ·         Where TO is ratio of total output of two agents in coupled
> positions (not necessarily with each other) with identical objective

(e.g.
> to win a race or impregnate an egg); here, sperm or cyclist; in the case

of
> sperm, millijoules; for cyclists, calories
>
> ·         T is total time spent in coupled positions and travelling at
> mutually faster velocities than achievable in isolation
>
> ·         %E is percent energy savings in coupled formation
>
> ·         Wa is the maximum sustainable power output; picoNewtons for
sperm,
> watts for cyclists of stronger agent A (cyclist or sperm) at a given
moment
> , assuming that in a competitive situation, agents are travelling as fast
as
> their metabolisms will allow.
>
> ·         Wb is the maximum sustainable power output at a given moment of
> weaker agent B, again assuming that in a competitive situation, agents
> travel as fast as metabolisms will allow.
>
>
>
> For example (quantities and units for illustration only): if stronger
sperm
> A has max sustainable output of 50pN, and B has max sustainable output of
> 45pN, and A saves an average of 10% output when coupled and spends a
total
> of 10 minutes coupled, total output for A is 50-5*10, or 450mj, while the
> weaker sperm saves no energy when coupled, but spends 11 minutes in
coupled
> positions, we have 45-0*11, 495; and 450/495 = 0.91. Thus where this
ratio
> is <1, the weaker sperm potentially can be ahead of the stronger sperm
over
> the duration of the coupling interactions.  Thus this ratio indicates why
it

> is not necessarily the case that stronger sperm will impregnate the egg.
>
>
>
>
>
>
>
> ============================================================
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============================================================
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[Hugh Trenchard]

Thanks for taking a peek at my post. Great questions, and they help me to
see how/where my descriptions can be clarified.

On the paradox part - that is one of the really interesting features of a
peloton: the energy savings effect of drafting narrows the range of fitness
between the strongest and weakest riders.  In contrast, think of a pack of
runners of varying fitness levels.  There is negligible drafting effect  -
there is some, esp if running into a headwind, but overall it's small enough
that it can be ignored for this illustration.  Say there are 50 runners, all
separated incrementally by 1% difference in fitness; say they run a couple
of miles. If they all start off slowly at say the max speed of the slowest
runner, they can all run in a big group, separated only by enough distance
between them to keep them from kicking and elbowing each other.  As they
pick up speed, the group thins into a line and are separated incrementally
by distances that correspond to their differences in fitness.  In the space
of two miles, they all finish individually in a single long line according
to their fitness, and it can be predicted accurately where runners will
finish if you know their starting levels of fitness.

This is not the case with a peloton.  For example at 25mph, riders can save
at least 25% by drafting (approx savings 1%/mph) - all the riders who are
within 25% fitness of the fastest rider can ride together even at the max
speed of the strongest rider.   So their fitness levels are effectively
narrowed, and they can all finish together as a group (ie. globally coupled
by finishing within drafting range of each other), and so the paradox.  Part
of the paradox is also that, while fitness levels are effectively narrowed
by drafting, it means, conversely, that a broader range of fitness levels
can ride together in a group, which maybe isn't something that is clear from
my initial post (though it is certainly implied).  Also, there are other
important things going on in a peloton which precede the sorting of riders
into groups, some of which I see I do need to clarify to make my model
clearer.

Of these, particularly important are 1) the occurrence of peloton rotations,
and 2) points of instability when riders are forced into positions where
they do not have optimal drafting advantage. Below a certain output
threshold, when all drafting riders in a group are sufficiently below max
output, riders have sufficient energy to shift relative positions within the
peloton, and in this particular phase, a self-organized rotational pattern
forms whereby riders advance up the peripheries and riders are forced
backward down the middle of the peloton. However, instabilities in pace
occur along the way, caused by such things as course obstacles, hills (when
lower speeds reduce drafting advantage, but when output may be at least as
high), cross-winds, narrowing of the course, or short anaerobic bursts among
riders at the front - all of which cause splits (i.e. PDR>1 at these
points).   In a competitive situation, instabilities occur frequently
causing temporary splits at various places in the peloton, but these are
often closed when the cause of the instability has ceased.  Sorting thus
occurs according to some combination of peloton rotations in which stronger
riders are able to get to the front and the continual splits in the peloton
at points of instability and reintegrations. I would need to develop the
model some more to show this as an equation (though I touch on a basic
version of it in my Appendix).

For sperm, I don't know what the initial state of the aggregates are when
they begin their travels, but I am assuming (perhaps quite incorrectly),
that there is some initial phase in which they are mixed (such as cyclists
on a starting line), and then they begin to sort as they increase speed.
During the process, they aggregate like cyclists because a broader range of
fitness levels can aggregate together (causing an effective narrowing of
fitness). As in a peloton, there are  instabilities that allow for
continuous re-adjustments to the relative positions of all the sperm, and
over time they begin to sort into groups where each have fitness levels
closer to the average.  This is my hypothesis, at least.

On the second last question, there would be an advantage to sperm among the
first pulse aggregation if all the pulsed aggregations do not mix first, but
the principles apply to each aggregation.  However, I don't know whether
there is some other process of mixing first among all the pulses of sperm
aggregations before they begin traveling (I imagine I could find the answer
in the literature), in which case there could easily be a sperm in,  say,
the second pulse, which could end up impregnating the egg.

I don't know about the kamikaze sperm - I'll leave that one for now!  But I
do remember that scene from the movie as clear as day!

In any event, my aim is really to ask the question - are there energetic and
coupling principles that allow sperm to end up in groups which otherwise
appear to have occurred because genetically related sperm can somehow
identify each other?   I am really only suggesting the existence of some
dynamics of the sperm aggregations that could be studied for, which don't
yet appear to have been addressed.

Hugh

----- Original Message -----
From: "Nicholas Thompson" <[hidden email]>
To: <[hidden email]>
Sent: Friday, March 26, 2010 8:04 PM
Subject: Re: [FRIAM] Sperm pelotons; article in Nature

> This is fun to think about.  Hopefully, REC will help me:
>
> Is there a paradox here.  let it be the case that sperm sort themselves by
> fitness;  let it further be the case that sperm in peletons have an
> advantage over sperm that dont.  Isnt it now the case that sperm are no
> longer sorting themselves by fitness?
>
> Ok, forget that:  so let be the case that "fitness" is not defined by
> fertization probability, but more in the sense of "physical fitness".
> Some
> of the sperm go to the gym, and some don't.  Or some are more muscular
> than
> others.  So let it be the case that sperm sort themselves by swimming
> speed. The more muscular sperm swim side by side and the less muscular
> sperm swim side by side.  But wait a minute, other things being equal
> wouldnt everybody bet the peleton effect?  Ok,  forget THAT, too.
>
> All these models assume that everbody starts from the same starting point,
> right?  Are they  jostling at the starting gate in the prostate as they
> are
> mixed with the seminal fluid.  Is there an advantage to being in the first
> pulsation?  So f orth.  Wouldnt these factors overwhelm the peleton
> effect?
>
> And, what about the kamakaze sperm, that stick pumps in the spokes of
> unrelated sperm as in that unforgettable scene in Breaking Away.
>
> Ok.  Sorry.  Forget the whole thing.  I do so like metaphors.
>
> Nick
>
> Nicholas S. Thompson
> Emeritus Professor of Psychology and Ethology,
> Clark University ([hidden email])
> http://home.earthlink.net/~nickthompson/naturaldesigns/
> http://www.cusf.org [City University of Santa Fe]
>
>
>
>
>> [Original Message]
>> From: Hugh Trenchard <[hidden email]>
>> To: The Friday Morning Applied Complexity Coffee Group
>> <[hidden email]>
>> Date: 3/26/2010 8:38:22 PM
>> Subject: [FRIAM]  Sperm pelotons; article in Nature
>>
>> On February 12, Roger Critchlow posted a reference to "sperm pelotons",
>> which inspired me to read the Nature article and to think a bit about how
>> principles of peloton interactions could be applied to sperm
> aggregations.
>> I've outlined some thoughts below.
>>
>>
>>
>> __________________________________________
>>
>> DRAFT
>>
>>
>>
>> Applications of a peloton model to sperm aggregration dynamics
>>
>> An analysis of article: Fisher, H., Hoekstra, H. (2010) Competition
> drives
>> cooperation among closely related sperm of deer mice. Nature. Vol. 463,
> 11
>> Feb 801-803
>>
>> Hugh Trenchard
>>
>>
>> Abstract
>>
>> The Nature article by Fisher and Hoekstra suggests that a mechanism
> exists
>> among the sperm of certain species of mice to identify genetic relatives.
>> The identification mechanism itself is not apparent and, based upon
>> observations of analogous processes in bicycle pelotons, an alternative
>> hypothesis is suggested.  There are similarities between bicycle pelotons
>> and sperm aggregations: they are both competitive dynamical systems, and
>> there are energy savings mechanisms by which agents couple and facilitate
>> self-organized aggregate formations.  A model for the division of a
> peloton
>> at critical output levels is shown and suggested as analogous to certain,
>> but not all, sperm aggregations, and a model for the relative energy
>> consumption of coupled and non-coupled aggregates is shown, which
> suggests
>> how sub-aggregates may form that are composed of agents within a narrowed
>> fitness range, and also why the strongest individual agents may not
> always
>> reach the target objective first.  This suggests that no mechanism is
>> required for the identification of genetic relatives, but that sorting
>> occurs according to a self-organized metabolic process whereby sperm with
>> close fitness levels will aggregate.  Sorting among sperm is hypothesized
> to
>> occur at a critical output threshold, and is more likely to occur among
>> promiscuous species than monogamous species because sperm velocity of
>> monogamous species may not be high enough to reach the critical sorting
>> threshold.  Genetically related sperm are more likely to have closer
> average
>> fitness levels, and so will naturally sort into groups composed of
>> predominantly related sperm. Thus proposed is an alternative framework by
>> which to analyze the data.
>> _______________________
>>
>>
>>
>>
>>
>> Introduction
>>             Fisher and Hoekstra (2010) provide evidence that supports the
>> hypothesis that sperm identify related sperm, aggregate and cooperate
> with
>> them and, through increased velocity when travelling in aggregations,
>> provide an advantage to genetically related sperm in advancing one of
> their
>> kind to impregnate the egg. The authors report a species of mouse whose
>> sperm exhibits "the ability to recognize sperm based on genetic
> relatedness
>> and preferentially cooperate with the most closely related sperm." The
>> question was raised: "how do sperm identify their brothers?" (FRIAM,
> 2010).
>> The question reveals a problem in Fisher's and Hoekstra's analysis, and a
>> clear mechanism for this identification process does not appear to be
>> suggested in their article.
>>
>> Observations of peloton dynamics allow an alternative explanation to the
>> cooperative aggregates that Fisher and Hoekstra (2010) have observed.
> Here
>> presented, instead, is the hypothesis that any aggregation among
> genetically
>> related sperm is coincidental to what is better explained by aggregates
> that
>> form due to coupling among groups of sperm as a result of an energy
> savings
>> effect that occurs when sperm travel closely together, an effect that is
>> similar to drafting in a bicycle peloton. This is a self-organized
> process
>> and, as such, no mechanism is required for sperm to identify genetically
>> related sperm to adjust their positions to be near each other.  This
> process
>> includes a sorting of individual sperm into groups with proportionately
> high
>> numbers of sperm whose swimming fitness is closest to their own.
>> Genetically related sperm are more likely to have similar swimming
> fitness
>> levels than are unrelated sperm.  Hence grouping is based upon swimming
>> fitness and not genetic relatedness, which also partially explains why
>> aggregates are not entirely homogenous according to relatedness:
> genetically
>> unrelated sperm with fitness levels near others, who may be related, will
>> group with them.
>>
>> For simplicity, here this self-organized energetic process is referred to
> as
>> drafting, although for sperm the energy savings mechanism is a
> hydrodynamic
>> one (Lauga and Powers, 2009; Woolley et al, 2009).  Similarly, the
>> interactive dynamic between sperm that allows for this energy savings to
>> occur is referred to as coupling.  Coupling of this nature has been
>> described as a synchronization of flagellar motion and optimal
> positioning
>> of sperm-heads for friction reduction and increased sperm velocities when
>> travelling in coupled formations as opposed to individually (Woolley, et
> al,
>> 2009). Woolley et al (2009) describe the mechanism for coupling in bull
>> sperm as follows:
>>
>> The subject of the present study, the flagellar synchronisations,
> resulted
>> from chance contacts between individual spermatozoa. These events will be
>> called 'conjunctions'. In a few instances, the two spermatozoa separated
>> again after a period of conjunction and they resumed the swimming speeds
> and
>> beat frequencies that they had shown before the conjunction.
>>
>>
>>
>>     Woolley et al. (2009) go on to show distinct increases in mutual
> speeds
>> when coupled (i.e. in conjunction states).  Their article does not,
> however,
>> appear to discuss overall average savings in energy as sperm accelerate
> and
>> decelerate while alternating between conjunctive and separated states
>> between different sets of coupled sperm, nor do they appear to discuss
> the
>> durations of conjunctions/separations, which would provide clues as to
>> relative differences in inherent fitness and whether sperm aggregations
> form
>> with sperm whose range of fitness is relatively narrow.  Here it is
>> hypothesized that this is, however, what does in fact occur:  this
> narrowed
>> fitness range among sperm sub-aggregates due to sorting is more likely to
> be
>> the mechanism underlying the genetically related sperm aggregations in
> the
>> Fisher and Hoekstra (2010) findings.
>>
>> The Woolley et al (2009) article suggests that, similarly to cyclists who
>> save energy by coupling in a peloton, it is unnecessary for sperm to be
> of
>> equal physical fitness to travel at the same (mutually increased) speed:
> to
>> travel at equal velocity while being of unequal fitness is facilitated by
> a
>> coupled energy savings mechanism.  Similarly, Riedel et al (2005), and
> Lauga
>> and Powers (2009), for example, appear to support the notion that there
> is
>> in fact some form of energy savings occurring among sperm aggregates.
>>
>>
>>
>>
>>
>> The peloton sorting model
>>
>> In bicycle pelotons, drafting allows riders within a range of output
>> capacities to sustain the same speed: weaker riders drafting can maintain
>> the same speed as stronger riders ahead according to the equation
>>
>>                         PDR = (Wa-Wb/Wa) / D*100
>>
>> ¡  Wa is maximum sustainable power (watts) of cyclist A at any given
> moment
>>
>> ¡  Wb is maximum sustainable power of cyclist B at any given moment
>>
>> ¡  D/100  is the percent energy savings at the speed travelled
>>
>>
>>
>> This is referred to as the Peloton Divergence Ratio (PDR) (Trenchard,
> 2009;
>> 2005). Cyclists save energy by drafting at approximately 1% per mile an
> hour
>> (Hagberg and McCole, 1990).  So, if for example, cyclists are traveling
> at
>> 25 mph, they save approximately 25% energy by drafting riders ahead.
>> Extending the illustration, if stronger cyclist A has a maximum
> sustainable
>> output at 400w at 25mph, and cyclist B has a maximum sustainable output
> of
>> 300w, cyclist B could not sustain the same speed as cyclist A if they
> were
>> travelling individually and without drafting.  Thus where cyclist B has
> only
>> 75% the output capacity of cyclist A, PDR = (400-300/400) /D*100; PDR=1.
> As
>> long as PDR is <1, cyclists can maintain the same speed.  If PDR>1,
> cyclists
>> will not be able to maintain the same speed and will diverge, or
> decouple.
>> So, at a speed of 25mph, all cyclists within a range of 25% output
> capacity
>> can travel at the same speed.
>>
>> Here it is suggested that PDR applies to certain types of sperm
>> aggregations, though not necessarily to all types, as there are several
>> different types of sperm morphology (Immler, et al. 2007), and their
>> respective energy savings mechanisms therefore cannot be assumed to be
> the
>> same.  In fact, PDR does not appear to apply to the Woolley et al (2009)
>> bull sperm observations, although it may to the Riedel (2005)
> observations,
>> the Moore et al. (2002) and Immler (2007) observations of "train"
>> aggregations, which in pelotons occur during a distinctive phase of
> energy
>> output when all riders are riding at or near maximum sustainable speeds,
> or
>> when riders are at or near PDR=1.   The phase is unstable and small
>> increases in speed or disturbances in rider positioning can put riders at
>> PDR>1 and precedes peloton separations and the formation of sub-pelotons.
>>
>> When cyclists in a peloton approach PDR=1,  a sorting process occurs
> whereby
>> sub-pelotons form that are composed of cyclists within a smaller range of
>> inherent fitness levels; i.e. each cyclist in the group has an inherent
>> fitness level (max sustainable output) that is closer to the average of
> the
>> sub-group than it is to the larger aggregate.  When peloton divisions
> occur
>> at points of instability (PDR >1) and cyclists in a competitive situation
>> exert maximal efforts to remain among the composition of the group ahead,
>> but are unable to do so, it is self-evident that the average fitness of
> the
>> group behind is less than that ahead, and that each of the groups contain
>> cyclists of closer average fitness than when among the undivided
> aggregate.
>>
>> The range of fitness within each sub-group is also effectively narrowed
>> further by the drafting process, as evidenced by the fact that
> sub-pelotons
>> in a mass-start bicycle race finish a race with nearly identical
> finishing
>> times (eg. see data in Trenchard, H., Mayer-Kress, G., 2005). This would
> not
>> be self-evident or a reasonable conclusion if the groups were not all
>> proceeding at maximum sustainable outputs, but had divided for
>> non-competitive reasons.
>>
>> This conclusion, however, does not preclude the possibility that some
>> cyclists with fitness levels which could sustain them in faster groups do
>> end up in slower groups (i.e. fitness levels that are substantially above
>> the average of the group), and so there may be a small proportion of
>> cyclists with fitness levels that overlap the ranges of different groups,
> as
>> would there be among sperm sub-aggregates.
>>
>> The sorting process and formation of aggregates with close average
> fitness
>> is well illustrated by imagining a peloton composed of 75 cyclists with a
>> broad range of abilities: 25 cyclists are professional level and can
> sustain
>> speeds of 50k an hour on the flat without drafting, 25 cyclists are
> medium
>> amateur level and can sustain speeds of 30km on the flat without
> drafting;
>> 25cyclists are kids who can sustain speeds of 15km per hour on the flat
>> without drafting.  If they all start together, the peloton is 75 strong
> up
>> to approximately 20km/h (because the kids can draft, they can go faster
> than
>> they could without drafting); at 21 km/h, the peloton sorts into two
> groups:
>> 25 kids, and 50 medium and pro cyclists.  The group of 50 accelerates,
> and
>> when they travel at approximately 36km/h the peloton divides again.  It
>> divides at 36km/h and not 30km/h because the medium-level riders can
> draft
>> up to speeds approximately 20 percent faster than they could achieve on
>> their own without drafting.  When speeds of 36km/h are sustained,
> eventually
>> all the medium-level cyclists will be separated from the professional
>> cyclists, and most, if not all, will end up together in a group.  At this
>> point the original peloton has divided into three groups containing
> riders
>> with fitness levels near to the average of the group.  In an actual
>> competition and peloton that is composed of all professional riders, the
>> sorting process is more subtle because average fitness of all the
> cyclists
>> is very close from the outset, but the effect is fundamentally the same.
>>
>>
>>
>> Applying the peloton model to sperm aggregations and the Fisher and
> Hoekstra
>> findings
>>
>> Here it is hypothesized that a similar sorting dynamic occurs in sperm
>> aggregations and may provide a clue as to the composition of the
>> sub-aggregates and the proportional representation of conspecific and
>> heterospecific sperm in any given aggregate, as identified by Fisher and
>> Hoekstra (2010).  Thus if the sperm of two males, say heterospecific in
> the
>> first example the authors provide, is mixed into an initial single
>> aggregate, the aggregate will begin to divide according to PDR as the
> sperm
>> accelerate. Sorting occurs as weaker sperm end up being "dropped" into
>> trailing sub-aggregates, as in the peloton illustration above.  Thus, if
> a
>> set of sperm from an individual conspecific male are, as a group, fitter
>> than those of the heterospecific competitor, there will be a
> self-organized
>> tendency for sperm of close physical fitness to group together.  Some
>> individual sperm from other groups, however, will be capable of
> sustaining
>> the speed of fitter sperm if they group with fitter sperm, as long as
> they
>> are at PDR<1  The proposition is thus that genetically related sperm are
>> naturally closer in physical fitness and therefore will tend to aggregate
>> together through self-organized coupling dynamics, as presented here.
>>
>> The composition of sperm aggregates is thus determined by individual
> sperm
>> fitness levels and the energy savings due to drafting at the velocity
>> travelled.  Divergences in the aggregates occur at critical individual
>> output/speed levels.  This is particularly so in the case of the
> promiscuous
>> species, P. maniculatus, and here it is assumed that sperm in a
> competitive
>> situation naturally swim at or near maximum sustainable speeds.  This is
> a
>> reasonable assumption in a competitive situation, in which all sperm are
>> seeking to reach the egg first.
>>
>> However, as indicated in the Fisher and Hoekstra article, in the case of
> P.
>> polionatus, the monogamous species, sperm may not travel at or near
> maximum
>> sustainable speeds, which suggests that the same degree of sorting does
> not
>> occur as among their faster swimming P. maniculatus counterparts.  This
>> provides an explanation why P. polionatus sperm tend to mix
>> indiscriminately, as the authors describe (see Table 1); i.e. the sperm
> have
>> adapted to swimming at less than maximum speeds as an intrinsic
>> characteristic of monogamous species, and the sorting of sperm into
> groups
>> with nearly equal fitness does not occur because the critical output
>> threshold is not reached for this to happen.
>>
>> Table 1 summarizes findings presented in the Fisher and Hoekstra article
> and
>> provides an alternative peloton model explanation.  Fisher and Hoekstra
> show
>> results for three experiments involving different combinations of mouse
>> species sperm mixes.  Table 1 summarizes both the results of the Fisher
> and
>> Hoekstra study, and the alternative peloton model explanation:
>>
>>
>>      Test
>>      Result
>>      Peloton model explanation
>>
>>       1
>>      Sperm from one heterospecific (P. polionotus) male and one
> conspecific
>> (P. maniculatus) male are mixed in vivo assay
>>      "found that overall groups were composed of significantly more
>> conspecific sperm than expected at random"
>>      Sperm from each of the conspecific males exhibit closer
> physiological
>> fitness than as between heterospecifics; i.e. conspecific males have
> average
>> fitness close to each other, as do rival heterospecifics to each other .
>> Some sperm for each sets, however, exhibit close physiological fitness
>> levels, and these represent the proportion of the aggregates that are not
>> from conspecific males. There are also percentages of each of
>> heterospecifics and conspecifics whose fitnesses are such that they are
>> capable of travelling with groups, but which are "trapped" in the slower
>> travelling groups.
>>
>>       2
>>      Sperm from two unrelated male P. maniculatus, a promiscuous species,
>> are mixed
>>      "sperm group significantly more often with sperm of the same male
> than
>> expected at random"
>>      The explanation above applies to the related conspecific maniculatus
>> males
>>
>>       3
>>      Sperm from two unrelated conspecific males of P. polionatus, a
>> monogamous species, are mixed
>>      "aggregations form indiscriminately in assays"
>>      The speed at which these sperm aggregations travel is relevant.  It
> may
>> be that the sperm of monogamous species travel slower (due to decreased
>> competition) than the critical speed at which self-organized sorting
> occurs.
>>
>>       4
>>      Sperm from related P. maniculatus was mixed
>>      "found a greater proportion of sperm from the same male grouped
>> together than was expected at random."
>>      The explanation in cases 1 and 2 above applies to the related
>> conspecific maniculatus males
>>
>>
>> Table 1
>>
>> In cases 1,2 and 4, the sorting process described in the foregoing
> provides
>> a reasonable alternative explanation to the formation of sperm
> aggregrations
>> with close average fitness, and the proposition that it is likely that
> sperm
>> of one male have closer average fitness than another male, whether it is
>> related or not.  Some proportion of the two sets of sperm will mix, but
> at
>> the critical threshold when sorting occurs, sperm with nearest average
>> fitness will aggregate.
>>
>> In case 3, the lower vitality of monogamous sperm, as the authors'
> finding
>> indicate, and the smaller testes of P. polionatus suggests that sperm
>> swimming speeds are slower and/or do not proceed at near maximal output
>> levels.  The slower sperm speeds of monogamous species is supported by
> other
>> finding (Nascimento, 2008; Fitzpatrick et al. 2009), although it is not
>> clear whether sperm are simply slower with a lesser maximum output
> capacity,
>> or whether they are in fact capable of swimming faster, but simply do
> not.
>> If the peloton model holds, then the inference is that the sperm of
>> monogamous species are capable of swimming faster but do not do so and,
> as a
>> result, are less likely to reach the critical output threshold by which
> they
>> will sort into sub-aggregates that contain sperm of near equal fitness
>> levels.  These relative speeds and output levels should be investigated
> and
>> confirmed.
>>
>>
>>
>> Conclusion
>>
>> The analysis here presents an alternative hypothesis for the findings
>> presented in the Fisher and Hoekstra article. Based upon analogous
> behavior
>> observed in bicycle-pelotons, it provides an analytical and experimental
>> framework by which existing data could be re-analyzed or further
> experiments
>> conducted to test for the observations and principles outlined.
>>
>> References
>>
>>
>>
>> FRIAM email listserv Feb 12, 2010, R. Critchlow. Vertical axis windmills
> and
>> sperm pelotons.
>>
>>
>>
>> Hagberg, J. and McCole, S. 1990.  The effect of drafting and aerodynamic
>> equipment on energy expenditure during cycling. Cycling Science 2:20.
>>
>> Immler, S., Harry D.M. Moore, H., William G. Breed, W., Birkhead, R.
> (2007).
>> By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent
>> Sperm, PLoS ONE. 2(1): e170.
>>
>> Published online 2007 January 24.
>>
>>
>>
>> Lauga, E., Powers, T. The hydrodynamics of swimming microorganisms.  Rep.
>> Prog. Phys. 72 (2009) 096601
>>
>>
>> Moore, H., Dvorakova, K., Jenkins, N. Breed., W. (2002). Exceptional
> sperm
>> cooperation in the wood mouse. Nature 418, 174-177
>>
>>
>> Nascimento JM, et al.(2008) The use of optical tweezers to study sperm
>> competition and motility in primates. J R Soc Inter 5:297-302. Published
>> online 2007 July 24. doi: 10.1098/rsif.2007.1118.
>>
>> Fitzpatrick, J., Montgomerie, R., Desjardins, J., Kelly, S., Kolm, N.,
>> Balshine, S. Female promiscuity promotes the evolution of faster sperm in
>> cichlid fishes PNAS January 27, 2009 vol. 106 no. 4 1128-1132
>>
>>
>> Riedel, et al. 2005. A Self-Organized Vortex Array of Hydrodynamically
>> Entrained Sperm Cells
>>
>> Science 8 July 2005: 300-303
>>
>> Trenchard, H., Mayer-Kress, G.  (2005) Self-organized oscillator coupling
>> and synchronization in bicycle pelotons during mass-start bicycle racing.
>> Intl Conference on Control and Synchronization of Dynamical Systems. Oct
> 4-7
>> Leon, Gto. Mexico.
>>
>>
>>
>> Trenchard, H.  (2009).  Self-organized coupling dynamics and phase
>> transitions in bicycle pelotons.  AAAI Fall Symposium, Arlington VA.
>> Technical Report Series FS-09-03.
>>
>>
>>
>> Woolley, D., Crockett, R., Grook. W., Revell, S. (2009). A study of
>> synchronisation between the flagella of bull spermatozoa, with related
>> Observations. The Journal of Experimental Biology 212, 2215-2223
>>
>>
>>
>> Yang, Y., Elgeti, J, Gompper, G. (2008) Cooperation of sperm in two
>> dimensions: synchronization, attraction, aggregation through dynamic
>> interactions. Phys Rev. E. 061903
>>
>>
>>
>>
>>
>> Appendix A
>>
>> Further development of the peloton/sperm aggregation model
>>
>> Note that PDR is a useful model if an energy savings mechanism exists
>> whereby one of two coupled sperm benefits from the energy savings
> mechanism,
>> while the other does not.  This may be the mechanism in the mouse species
>> described in the Moore (2002) and Immler (2007) articles, as indicated by
>> the "train" formation, which is similar to "single paceline" peloton
>> formations when cyclists are aligned near or at PDR=1 to each other
>> (Trenchard, 2009; 2005).
>>
>>  There do appear, however, to be other energy savings mechanisms in sperm
>> aggregates, such as for example the conjunction and synchronized dynamic
> of
>> bull sperm (Woolley et al, 2009).  In a sperm conjunction (Woolley et al,
>> 2009), the PDR equation does not strictly apply and must be adjusted
> because
>> the stronger sperm also appears to benefit from the coupled formation,
> which
>> does not occur to any significant degree between coupled cyclists; i.e.
> in a
>> peloton the front riding cyclist does not receive any reduction in output
>> from the rider behind, while the rider behind benefits substantially by
>> drafting; for bull sperm, it appears that both coupled sperm benefit by
>> increased velocity.
>>
>> This leads to a further hypothesis that the stronger sperm increases
> speed
>> with some reduction in metabolic cost, while the weaker sperm increases
>> speed with little or no change in metabolic cost, although they both
> travel
>> faster than they would individually.  Thus it is the stronger sperm that
>> benefits by energy savings, while the weaker sperm benefits by increased
>> speed, but with no savings in energy.  There is an implication that the
>> stronger sperm will always be able to advance to the front of the sperm
>> aggregation faster than weaker sperm.  However, this is not necessarily
> so,
>> as it depends on the relative durations of coupling and separations.
> That
>> is to say, a weaker sperm could advance farther and faster than a
> stronger
>> sperm if it spends sufficiently more time coupled than a stronger sperm
>> which may spend relatively more time isolated.  Thus the faster sperm are
>> not necessarily those that are stronger, but those whose proportion of
> total
>> coupling time exceeds the percent differences in their relative fitness
>> levels.
>>
>> The following model is descriptive for coupled organisms that may
> alternate
>> durations of time spent coupled with time spent non-coupled, and which
>> mutually benefit from coupling because it accounts for the proportions of
>> total time spent both saving energy in coupled positions and not saving
>> energy in non-coupled positions.  It is a simplified model because there
> are
>> other factors that affect total output than time spent in energy-saving
>> positions (coupled) and positions where there is no energy savings.
>> However, it provides insight into the energetic dynamics of coupled
> agents
>> of varying degrees of fitness and why they do not necessarily achieve
>> positions based on inherent fitness.
>>
>>
>>
>> TO = Wa-(Wa*%E) * T)  /  Wb-(Wb*%E) * T)
>>
>>
>>
>> ·         Where TO is ratio of total output of two agents in coupled
>> positions (not necessarily with each other) with identical objective
> (e.g.
>> to win a race or impregnate an egg); here, sperm or cyclist; in the case
> of
>> sperm, millijoules; for cyclists, calories
>>
>> ·         T is total time spent in coupled positions and travelling at
>> mutually faster velocities than achievable in isolation
>>
>> ·         %E is percent energy savings in coupled formation
>>
>> ·         Wa is the maximum sustainable power output; picoNewtons for
> sperm,
>> watts for cyclists of stronger agent A (cyclist or sperm) at a given
> moment
>> , assuming that in a competitive situation, agents are travelling as fast
> as
>> their metabolisms will allow.
>>
>> ·         Wb is the maximum sustainable power output at a given moment of
>> weaker agent B, again assuming that in a competitive situation, agents
>> travel as fast as metabolisms will allow.
>>
>>
>>
>> For example (quantities and units for illustration only): if stronger
> sperm
>> A has max sustainable output of 50pN, and B has max sustainable output of
>> 45pN, and A saves an average of 10% output when coupled and spends a
> total
>> of 10 minutes coupled, total output for A is 50-5*10, or 450mj, while the
>> weaker sperm saves no energy when coupled, but spends 11 minutes in
> coupled
>> positions, we have 45-0*11, 495; and 450/495 = 0.91. Thus where this
> ratio
>> is <1, the weaker sperm potentially can be ahead of the stronger sperm
> over
>> the duration of the coupling interactions.  Thus this ratio indicates why
> it
>> is not necessarily the case that stronger sperm will impregnate the egg.
>>
>>
>>
>>
>>
>>
>>
>> ============================================================
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>> Meets Fridays 9a-11:30 at cafe at St. John's College
>> lectures, archives, unsubscribe, maps at http://www.friam.org
>
>
>
>

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>



============================================================
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[Nick Thompson]

Hugh,

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now.

 Nick

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied Complexity
Coffee Group <[hidden email]>
> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great questions, and they help me to
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a
> peloton: the energy savings effect of drafting narrows the range of
fitness
> between the strongest and weakest riders.  In contrast, think of a pack
of
> runners of varying fitness levels.  There is negligible drafting effect
-
> there is some, esp if running into a headwind, but overall it's small
enough
> that it can be ignored for this illustration.  Say there are 50 runners,
all
> separated incrementally by 1% difference in fitness; say they run a
couple
> of miles. If they all start off slowly at say the max speed of the
slowest
> runner, they can all run in a big group, separated only by enough
distance
> between them to keep them from kicking and elbowing each other.  As they
> pick up speed, the group thins into a line and are separated
incrementally
> by distances that correspond to their differences in fitness.  In the
space
> of two miles, they all finish individually in a single long line
according
> to their fitness, and it can be predicted accurately where runners will
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save
> at least 25% by drafting (approx savings 1%/mph) - all the riders who are
> within 25% fitness of the fastest rider can ride together even at the max
> speed of the strongest rider.   So their fitness levels are effectively
> narrowed, and they can all finish together as a group (ie. globally
coupled
> by finishing within drafting range of each other), and so the paradox.
Part
> of the paradox is also that, while fitness levels are effectively
narrowed
> by drafting, it means, conversely, that a broader range of fitness levels
> can ride together in a group, which maybe isn't something that is clear
from
> my initial post (though it is certainly implied).  Also, there are other
> important things going on in a peloton which precede the sorting of
riders
> into groups, some of which I see I do need to clarify to make my model
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations,
> and 2) points of instability when riders are forced into positions where
> they do not have optimal drafting advantage. Below a certain output
> threshold, when all drafting riders in a group are sufficiently below max
> output, riders have sufficient energy to shift relative positions within
the
> peloton, and in this particular phase, a self-organized rotational
pattern
> forms whereby riders advance up the peripheries and riders are forced
> backward down the middle of the peloton. However, instabilities in pace
> occur along the way, caused by such things as course obstacles, hills
(when
> lower speeds reduce drafting advantage, but when output may be at least
as
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among
> riders at the front - all of which cause splits (i.e. PDR>1 at these
> points).   In a competitive situation, instabilities occur frequently
> causing temporary splits at various places in the peloton, but these are
> often closed when the cause of the instability has ceased.  Sorting thus
> occurs according to some combination of peloton rotations in which
stronger
> riders are able to get to the front and the continual splits in the
peloton
> at points of instability and reintegrations. I would need to develop the
> model some more to show this as an equation (though I touch on a basic
> version of it in my Appendix).
>
> For sperm, I don't know what the initial state of the aggregates are when
> they begin their travels, but I am assuming (perhaps quite incorrectly),
> that there is some initial phase in which they are mixed (such as
cyclists
> on a starting line), and then they begin to sort as they increase speed.
> During the process, they aggregate like cyclists because a broader range
of
> fitness levels can aggregate together (causing an effective narrowing of
> fitness). As in a peloton, there are  instabilities that allow for
> continuous re-adjustments to the relative positions of all the sperm, and
> over time they begin to sort into groups where each have fitness levels
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the
> first pulse aggregation if all the pulsed aggregations do not mix first,
but
> the principles apply to each aggregation.  However, I don't know whether
> there is some other process of mixing first among all the pulses of sperm
> aggregations before they begin traveling (I imagine I could find the
answer
> in the literature), in which case there could easily be a sperm in,  say,
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and

> coupling principles that allow sperm to end up in groups which otherwise
> appear to have occurred because genetically related sperm can somehow
> identify each other?   I am really only suggesting the existence of some
> dynamics of the sperm aggregations that could be studied for, which don't
> yet appear to have been addressed.
>
> Hugh
>
> ----- Original Message -----
> From: "Nicholas Thompson" <[hidden email]>
> To: <[hidden email]>
> Sent: Friday, March 26, 2010 8:04 PM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
>
> > This is fun to think about.  Hopefully, REC will help me:
> >
> > Is there a paradox here.  let it be the case that sperm sort themselves

by

> > fitness;  let it further be the case that sperm in peletons have an
> > advantage over sperm that dont.  Isnt it now the case that sperm are no
> > longer sorting themselves by fitness?
> >
> > Ok, forget that:  so let be the case that "fitness" is not defined by
> > fertization probability, but more in the sense of "physical fitness".
> > Some
> > of the sperm go to the gym, and some don't.  Or some are more muscular
> > than
> > others.  So let it be the case that sperm sort themselves by swimming
> > speed. The more muscular sperm swim side by side and the less muscular
> > sperm swim side by side.  But wait a minute, other things being equal
> > wouldnt everybody bet the peleton effect?  Ok,  forget THAT, too.
> >
> > All these models assume that everbody starts from the same starting

point,
> > right?  Are they  jostling at the starting gate in the prostate as they
> > are
> > mixed with the seminal fluid.  Is there an advantage to being in the

first

> > pulsation?  So f orth.  Wouldnt these factors overwhelm the peleton
> > effect?
> >
> > And, what about the kamakaze sperm, that stick pumps in the spokes of
> > unrelated sperm as in that unforgettable scene in Breaking Away.
> >
> > Ok.  Sorry.  Forget the whole thing.  I do so like metaphors.
> >
> > Nick
> >
> > Nicholas S. Thompson
> > Emeritus Professor of Psychology and Ethology,
> > Clark University ([hidden email])
> > http://home.earthlink.net/~nickthompson/naturaldesigns/
> > http://www.cusf.org [City University of Santa Fe]
> >
> >
> >
> >
> >> [Original Message]
> >> From: Hugh Trenchard <[hidden email]>
> >> To: The Friday Morning Applied Complexity Coffee Group
> >> <[hidden email]>
> >> Date: 3/26/2010 8:38:22 PM
> >> Subject: [FRIAM]  Sperm pelotons; article in Nature
> >>
> >> On February 12, Roger Critchlow posted a reference to "sperm pelotons",
> >> which inspired me to read the Nature article and to think a bit about

how

> >> principles of peloton interactions could be applied to sperm
> > aggregations.
> >> I've outlined some thoughts below.
> >>
> >>
> >>
> >> __________________________________________
> >>
> >> DRAFT
> >>
> >>
> >>
> >> Applications of a peloton model to sperm aggregration dynamics
> >>
> >> An analysis of article: Fisher, H., Hoekstra, H. (2010) Competition
> > drives
> >> cooperation among closely related sperm of deer mice. Nature. Vol. 463,
> > 11
> >> Feb 801-803
> >>
> >> Hugh Trenchard
> >>
> >>
> >> Abstract
> >>
> >> The Nature article by Fisher and Hoekstra suggests that a mechanism
> > exists
> >> among the sperm of certain species of mice to identify genetic

relatives.
> >> The identification mechanism itself is not apparent and, based upon
> >> observations of analogous processes in bicycle pelotons, an alternative
> >> hypothesis is suggested.  There are similarities between bicycle

pelotons
> >> and sperm aggregations: they are both competitive dynamical systems,
and
> >> there are energy savings mechanisms by which agents couple and
facilitate
> >> self-organized aggregate formations.  A model for the division of a
> > peloton
> >> at critical output levels is shown and suggested as analogous to
certain,
> >> but not all, sperm aggregations, and a model for the relative energy
> >> consumption of coupled and non-coupled aggregates is shown, which
> > suggests
> >> how sub-aggregates may form that are composed of agents within a
narrowed
> >> fitness range, and also why the strongest individual agents may not
> > always
> >> reach the target objective first.  This suggests that no mechanism is
> >> required for the identification of genetic relatives, but that sorting
> >> occurs according to a self-organized metabolic process whereby sperm
with
> >> close fitness levels will aggregate.  Sorting among sperm is
hypothesized
> > to
> >> occur at a critical output threshold, and is more likely to occur among
> >> promiscuous species than monogamous species because sperm velocity of
> >> monogamous species may not be high enough to reach the critical sorting
> >> threshold.  Genetically related sperm are more likely to have closer
> > average
> >> fitness levels, and so will naturally sort into groups composed of
> >> predominantly related sperm. Thus proposed is an alternative framework
by
> >> which to analyze the data.
> >> _______________________
> >>
> >>
> >>
> >>
> >>
> >> Introduction
> >>             Fisher and Hoekstra (2010) provide evidence that supports
the

> >> hypothesis that sperm identify related sperm, aggregate and cooperate
> > with
> >> them and, through increased velocity when travelling in aggregations,
> >> provide an advantage to genetically related sperm in advancing one of
> > their
> >> kind to impregnate the egg. The authors report a species of mouse whose
> >> sperm exhibits "the ability to recognize sperm based on genetic
> > relatedness
> >> and preferentially cooperate with the most closely related sperm." The
> >> question was raised: "how do sperm identify their brothers?" (FRIAM,
> > 2010).
> >> The question reveals a problem in Fisher's and Hoekstra's analysis,

and a
> >> clear mechanism for this identification process does not appear to be
> >> suggested in their article.
> >>
> >> Observations of peloton dynamics allow an alternative explanation to

the
> >> cooperative aggregates that Fisher and Hoekstra (2010) have observed.
> > Here
> >> presented, instead, is the hypothesis that any aggregation among
> > genetically
> >> related sperm is coincidental to what is better explained by aggregates
> > that
> >> form due to coupling among groups of sperm as a result of an energy
> > savings
> >> effect that occurs when sperm travel closely together, an effect that
is
> >> similar to drafting in a bicycle peloton. This is a self-organized
> > process
> >> and, as such, no mechanism is required for sperm to identify
genetically

> >> related sperm to adjust their positions to be near each other.  This
> > process
> >> includes a sorting of individual sperm into groups with proportionately
> > high
> >> numbers of sperm whose swimming fitness is closest to their own.
> >> Genetically related sperm are more likely to have similar swimming
> > fitness
> >> levels than are unrelated sperm.  Hence grouping is based upon swimming
> >> fitness and not genetic relatedness, which also partially explains why
> >> aggregates are not entirely homogenous according to relatedness:
> > genetically
> >> unrelated sperm with fitness levels near others, who may be related,

will
> >> group with them.
> >>
> >> For simplicity, here this self-organized energetic process is referred

to
> > as
> >> drafting, although for sperm the energy savings mechanism is a
> > hydrodynamic
> >> one (Lauga and Powers, 2009; Woolley et al, 2009).  Similarly, the
> >> interactive dynamic between sperm that allows for this energy savings
to
> >> occur is referred to as coupling.  Coupling of this nature has been
> >> described as a synchronization of flagellar motion and optimal
> > positioning
> >> of sperm-heads for friction reduction and increased sperm velocities
when
> >> travelling in coupled formations as opposed to individually (Woolley,
et
> > al,
> >> 2009). Woolley et al (2009) describe the mechanism for coupling in bull
> >> sperm as follows:
> >>
> >> The subject of the present study, the flagellar synchronisations,
> > resulted
> >> from chance contacts between individual spermatozoa. These events will
be
> >> called 'conjunctions'. In a few instances, the two spermatozoa
separated
> >> again after a period of conjunction and they resumed the swimming
speeds

> > and
> >> beat frequencies that they had shown before the conjunction.
> >>
> >>
> >>
> >>     Woolley et al. (2009) go on to show distinct increases in mutual
> > speeds
> >> when coupled (i.e. in conjunction states).  Their article does not,
> > however,
> >> appear to discuss overall average savings in energy as sperm accelerate
> > and
> >> decelerate while alternating between conjunctive and separated states
> >> between different sets of coupled sperm, nor do they appear to discuss
> > the
> >> durations of conjunctions/separations, which would provide clues as to
> >> relative differences in inherent fitness and whether sperm aggregations
> > form
> >> with sperm whose range of fitness is relatively narrow.  Here it is
> >> hypothesized that this is, however, what does in fact occur:  this
> > narrowed
> >> fitness range among sperm sub-aggregates due to sorting is more likely

to
> > be
> >> the mechanism underlying the genetically related sperm aggregations in
> > the
> >> Fisher and Hoekstra (2010) findings.
> >>
> >> The Woolley et al (2009) article suggests that, similarly to cyclists

who
> >> save energy by coupling in a peloton, it is unnecessary for sperm to be
> > of
> >> equal physical fitness to travel at the same (mutually increased)
speed:
> > to
> >> travel at equal velocity while being of unequal fitness is facilitated
by

> > a
> >> coupled energy savings mechanism.  Similarly, Riedel et al (2005), and
> > Lauga
> >> and Powers (2009), for example, appear to support the notion that there
> > is
> >> in fact some form of energy savings occurring among sperm aggregates.
> >>
> >>
> >>
> >>
> >>
> >> The peloton sorting model
> >>
> >> In bicycle pelotons, drafting allows riders within a range of output
> >> capacities to sustain the same speed: weaker riders drafting can

maintain

> >> the same speed as stronger riders ahead according to the equation
> >>
> >>                         PDR = (Wa-Wb/Wa) / D*100
> >>
> >> ¡  Wa is maximum sustainable power (watts) of cyclist A at any given
> > moment
> >>
> >> ¡  Wb is maximum sustainable power of cyclist B at any given moment
> >>
> >> ¡  D/100  is the percent energy savings at the speed travelled
> >>
> >>
> >>
> >> This is referred to as the Peloton Divergence Ratio (PDR) (Trenchard,
> > 2009;
> >> 2005). Cyclists save energy by drafting at approximately 1% per mile an
> > hour
> >> (Hagberg and McCole, 1990).  So, if for example, cyclists are traveling
> > at
> >> 25 mph, they save approximately 25% energy by drafting riders ahead.
> >> Extending the illustration, if stronger cyclist A has a maximum
> > sustainable
> >> output at 400w at 25mph, and cyclist B has a maximum sustainable output
> > of
> >> 300w, cyclist B could not sustain the same speed as cyclist A if they
> > were
> >> travelling individually and without drafting.  Thus where cyclist B has
> > only
> >> 75% the output capacity of cyclist A, PDR = (400-300/400) /D*100;

PDR=1.

> > As
> >> long as PDR is <1, cyclists can maintain the same speed.  If PDR>1,
> > cyclists
> >> will not be able to maintain the same speed and will diverge, or
> > decouple.
> >> So, at a speed of 25mph, all cyclists within a range of 25% output
> > capacity
> >> can travel at the same speed.
> >>
> >> Here it is suggested that PDR applies to certain types of sperm
> >> aggregations, though not necessarily to all types, as there are several
> >> different types of sperm morphology (Immler, et al. 2007), and their
> >> respective energy savings mechanisms therefore cannot be assumed to be
> > the
> >> same.  In fact, PDR does not appear to apply to the Woolley et al

(2009)
> >> bull sperm observations, although it may to the Riedel (2005)
> > observations,
> >> the Moore et al. (2002) and Immler (2007) observations of "train"
> >> aggregations, which in pelotons occur during a distinctive phase of
> > energy
> >> output when all riders are riding at or near maximum sustainable

speeds,
> > or
> >> when riders are at or near PDR=1.   The phase is unstable and small
> >> increases in speed or disturbances in rider positioning can put riders
at
> >> PDR>1 and precedes peloton separations and the formation of
sub-pelotons.
> >>
> >> When cyclists in a peloton approach PDR=1,  a sorting process occurs
> > whereby
> >> sub-pelotons form that are composed of cyclists within a smaller range
of
> >> inherent fitness levels; i.e. each cyclist in the group has an inherent
> >> fitness level (max sustainable output) that is closer to the average of
> > the
> >> sub-group than it is to the larger aggregate.  When peloton divisions
> > occur
> >> at points of instability (PDR >1) and cyclists in a competitive
situation
> >> exert maximal efforts to remain among the composition of the group
ahead,
> >> but are unable to do so, it is self-evident that the average fitness of
> > the
> >> group behind is less than that ahead, and that each of the groups
contain
> >> cyclists of closer average fitness than when among the undivided
> > aggregate.
> >>
> >> The range of fitness within each sub-group is also effectively narrowed
> >> further by the drafting process, as evidenced by the fact that
> > sub-pelotons
> >> in a mass-start bicycle race finish a race with nearly identical
> > finishing
> >> times (eg. see data in Trenchard, H., Mayer-Kress, G., 2005). This
would
> > not
> >> be self-evident or a reasonable conclusion if the groups were not all
> >> proceeding at maximum sustainable outputs, but had divided for
> >> non-competitive reasons.
> >>
> >> This conclusion, however, does not preclude the possibility that some
> >> cyclists with fitness levels which could sustain them in faster groups
do
> >> end up in slower groups (i.e. fitness levels that are substantially
above
> >> the average of the group), and so there may be a small proportion of
> >> cyclists with fitness levels that overlap the ranges of different
groups,
> > as
> >> would there be among sperm sub-aggregates.
> >>
> >> The sorting process and formation of aggregates with close average
> > fitness
> >> is well illustrated by imagining a peloton composed of 75 cyclists
with a

> >> broad range of abilities: 25 cyclists are professional level and can
> > sustain
> >> speeds of 50k an hour on the flat without drafting, 25 cyclists are
> > medium
> >> amateur level and can sustain speeds of 30km on the flat without
> > drafting;
> >> 25cyclists are kids who can sustain speeds of 15km per hour on the flat
> >> without drafting.  If they all start together, the peloton is 75 strong
> > up
> >> to approximately 20km/h (because the kids can draft, they can go faster
> > than
> >> they could without drafting); at 21 km/h, the peloton sorts into two
> > groups:
> >> 25 kids, and 50 medium and pro cyclists.  The group of 50 accelerates,
> > and
> >> when they travel at approximately 36km/h the peloton divides again.  It
> >> divides at 36km/h and not 30km/h because the medium-level riders can
> > draft
> >> up to speeds approximately 20 percent faster than they could achieve on
> >> their own without drafting.  When speeds of 36km/h are sustained,
> > eventually
> >> all the medium-level cyclists will be separated from the professional
> >> cyclists, and most, if not all, will end up together in a group.  At

this
> >> point the original peloton has divided into three groups containing
> > riders
> >> with fitness levels near to the average of the group.  In an actual
> >> competition and peloton that is composed of all professional riders,

the
> >> sorting process is more subtle because average fitness of all the
> > cyclists
> >> is very close from the outset, but the effect is fundamentally the
same.

> >>
> >>
> >>
> >> Applying the peloton model to sperm aggregations and the Fisher and
> > Hoekstra
> >> findings
> >>
> >> Here it is hypothesized that a similar sorting dynamic occurs in sperm
> >> aggregations and may provide a clue as to the composition of the
> >> sub-aggregates and the proportional representation of conspecific and
> >> heterospecific sperm in any given aggregate, as identified by Fisher

and
> >> Hoekstra (2010).  Thus if the sperm of two males, say heterospecific in
> > the
> >> first example the authors provide, is mixed into an initial single
> >> aggregate, the aggregate will begin to divide according to PDR as the
> > sperm
> >> accelerate. Sorting occurs as weaker sperm end up being "dropped" into
> >> trailing sub-aggregates, as in the peloton illustration above.  Thus,

if
> > a
> >> set of sperm from an individual conspecific male are, as a group,
fitter
> >> than those of the heterospecific competitor, there will be a
> > self-organized
> >> tendency for sperm of close physical fitness to group together.  Some
> >> individual sperm from other groups, however, will be capable of
> > sustaining
> >> the speed of fitter sperm if they group with fitter sperm, as long as
> > they
> >> are at PDR<1  The proposition is thus that genetically related sperm
are
> >> naturally closer in physical fitness and therefore will tend to
aggregate

> >> together through self-organized coupling dynamics, as presented here.
> >>
> >> The composition of sperm aggregates is thus determined by individual
> > sperm
> >> fitness levels and the energy savings due to drafting at the velocity
> >> travelled.  Divergences in the aggregates occur at critical individual
> >> output/speed levels.  This is particularly so in the case of the
> > promiscuous
> >> species, P. maniculatus, and here it is assumed that sperm in a
> > competitive
> >> situation naturally swim at or near maximum sustainable speeds.  This

is
> > a
> >> reasonable assumption in a competitive situation, in which all sperm

are
> >> seeking to reach the egg first.
> >>
> >> However, as indicated in the Fisher and Hoekstra article, in the case
of

> > P.
> >> polionatus, the monogamous species, sperm may not travel at or near
> > maximum
> >> sustainable speeds, which suggests that the same degree of sorting does
> > not
> >> occur as among their faster swimming P. maniculatus counterparts.  This
> >> provides an explanation why P. polionatus sperm tend to mix
> >> indiscriminately, as the authors describe (see Table 1); i.e. the sperm
> > have
> >> adapted to swimming at less than maximum speeds as an intrinsic
> >> characteristic of monogamous species, and the sorting of sperm into
> > groups
> >> with nearly equal fitness does not occur because the critical output
> >> threshold is not reached for this to happen.
> >>
> >> Table 1 summarizes findings presented in the Fisher and Hoekstra

article

> > and
> >> provides an alternative peloton model explanation.  Fisher and Hoekstra
> > show
> >> results for three experiments involving different combinations of mouse
> >> species sperm mixes.  Table 1 summarizes both the results of the Fisher
> > and
> >> Hoekstra study, and the alternative peloton model explanation:
> >>
> >>
> >>      Test
> >>      Result
> >>      Peloton model explanation
> >>
> >>       1
> >>      Sperm from one heterospecific (P. polionotus) male and one
> > conspecific
> >> (P. maniculatus) male are mixed in vivo assay
> >>      "found that overall groups were composed of significantly more
> >> conspecific sperm than expected at random"
> >>      Sperm from each of the conspecific males exhibit closer
> > physiological
> >> fitness than as between heterospecifics; i.e. conspecific males have
> > average
> >> fitness close to each other, as do rival heterospecifics to each other

.
> >> Some sperm for each sets, however, exhibit close physiological fitness
> >> levels, and these represent the proportion of the aggregates that are

not
> >> from conspecific males. There are also percentages of each of
> >> heterospecifics and conspecifics whose fitnesses are such that they are
> >> capable of travelling with groups, but which are "trapped" in the
slower
> >> travelling groups.
> >>
> >>       2
> >>      Sperm from two unrelated male P. maniculatus, a promiscuous
species,
> >> are mixed
> >>      "sperm group significantly more often with sperm of the same male
> > than
> >> expected at random"
> >>      The explanation above applies to the related conspecific
maniculatus
> >> males
> >>
> >>       3
> >>      Sperm from two unrelated conspecific males of P. polionatus, a
> >> monogamous species, are mixed
> >>      "aggregations form indiscriminately in assays"
> >>      The speed at which these sperm aggregations travel is relevant.
It

> > may
> >> be that the sperm of monogamous species travel slower (due to decreased
> >> competition) than the critical speed at which self-organized sorting
> > occurs.
> >>
> >>       4
> >>      Sperm from related P. maniculatus was mixed
> >>      "found a greater proportion of sperm from the same male grouped
> >> together than was expected at random."
> >>      The explanation in cases 1 and 2 above applies to the related
> >> conspecific maniculatus males
> >>
> >>
> >> Table 1
> >>
> >> In cases 1,2 and 4, the sorting process described in the foregoing
> > provides
> >> a reasonable alternative explanation to the formation of sperm
> > aggregrations
> >> with close average fitness, and the proposition that it is likely that
> > sperm
> >> of one male have closer average fitness than another male, whether it

is

> >> related or not.  Some proportion of the two sets of sperm will mix, but
> > at
> >> the critical threshold when sorting occurs, sperm with nearest average
> >> fitness will aggregate.
> >>
> >> In case 3, the lower vitality of monogamous sperm, as the authors'
> > finding
> >> indicate, and the smaller testes of P. polionatus suggests that sperm
> >> swimming speeds are slower and/or do not proceed at near maximal output
> >> levels.  The slower sperm speeds of monogamous species is supported by
> > other
> >> finding (Nascimento, 2008; Fitzpatrick et al. 2009), although it is not
> >> clear whether sperm are simply slower with a lesser maximum output
> > capacity,
> >> or whether they are in fact capable of swimming faster, but simply do
> > not.
> >> If the peloton model holds, then the inference is that the sperm of
> >> monogamous species are capable of swimming faster but do not do so and,
> > as a
> >> result, are less likely to reach the critical output threshold by which
> > they
> >> will sort into sub-aggregates that contain sperm of near equal fitness
> >> levels.  These relative speeds and output levels should be investigated
> > and
> >> confirmed.
> >>
> >>
> >>
> >> Conclusion
> >>
> >> The analysis here presents an alternative hypothesis for the findings
> >> presented in the Fisher and Hoekstra article. Based upon analogous
> > behavior
> >> observed in bicycle-pelotons, it provides an analytical and

experimental
> >> framework by which existing data could be re-analyzed or further
> > experiments
> >> conducted to test for the observations and principles outlined.
> >>
> >> References
> >>
> >>
> >>
> >> FRIAM email listserv Feb 12, 2010, R. Critchlow. Vertical axis

windmills
> > and
> >> sperm pelotons.
> >>
> >>
> >>
> >> Hagberg, J. and McCole, S. 1990.  The effect of drafting and
aerodynamic

> >> equipment on energy expenditure during cycling. Cycling Science 2:20.
> >>
> >> Immler, S., Harry D.M. Moore, H., William G. Breed, W., Birkhead, R.
> > (2007).
> >> By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent
> >> Sperm, PLoS ONE. 2(1): e170.
> >>
> >> Published online 2007 January 24.
> >>
> >>
> >>
> >> Lauga, E., Powers, T. The hydrodynamics of swimming microorganisms.

Rep.

> >> Prog. Phys. 72 (2009) 096601
> >>
> >>
> >> Moore, H., Dvorakova, K., Jenkins, N. Breed., W. (2002). Exceptional
> > sperm
> >> cooperation in the wood mouse. Nature 418, 174-177
> >>
> >>
> >> Nascimento JM, et al.(2008) The use of optical tweezers to study sperm
> >> competition and motility in primates. J R Soc Inter 5:297-302.

Published
> >> online 2007 July 24. doi: 10.1098/rsif.2007.1118.
> >>
> >> Fitzpatrick, J., Montgomerie, R., Desjardins, J., Kelly, S., Kolm, N.,
> >> Balshine, S. Female promiscuity promotes the evolution of faster sperm

in
> >> cichlid fishes PNAS January 27, 2009 vol. 106 no. 4 1128-1132
> >>
> >>
> >> Riedel, et al. 2005. A Self-Organized Vortex Array of Hydrodynamically
> >> Entrained Sperm Cells
> >>
> >> Science 8 July 2005: 300-303
> >>
> >> Trenchard, H., Mayer-Kress, G.  (2005) Self-organized oscillator
coupling
> >> and synchronization in bicycle pelotons during mass-start bicycle
racing.
> >> Intl Conference on Control and Synchronization of Dynamical Systems.
Oct

> > 4-7
> >> Leon, Gto. Mexico.
> >>
> >>
> >>
> >> Trenchard, H.  (2009).  Self-organized coupling dynamics and phase
> >> transitions in bicycle pelotons.  AAAI Fall Symposium, Arlington VA.
> >> Technical Report Series FS-09-03.
> >>
> >>
> >>
> >> Woolley, D., Crockett, R., Grook. W., Revell, S. (2009). A study of
> >> synchronisation between the flagella of bull spermatozoa, with related
> >> Observations. The Journal of Experimental Biology 212, 2215-2223
> >>
> >>
> >>
> >> Yang, Y., Elgeti, J, Gompper, G. (2008) Cooperation of sperm in two
> >> dimensions: synchronization, attraction, aggregation through dynamic
> >> interactions. Phys Rev. E. 061903
> >>
> >>
> >>
> >>
> >>
> >> Appendix A
> >>
> >> Further development of the peloton/sperm aggregation model
> >>
> >> Note that PDR is a useful model if an energy savings mechanism exists
> >> whereby one of two coupled sperm benefits from the energy savings
> > mechanism,
> >> while the other does not.  This may be the mechanism in the mouse

species
> >> described in the Moore (2002) and Immler (2007) articles, as indicated

by
> >> the "train" formation, which is similar to "single paceline" peloton
> >> formations when cyclists are aligned near or at PDR=1 to each other
> >> (Trenchard, 2009; 2005).
> >>
> >>  There do appear, however, to be other energy savings mechanisms in
sperm
> >> aggregates, such as for example the conjunction and synchronized
dynamic
> > of
> >> bull sperm (Woolley et al, 2009).  In a sperm conjunction (Woolley et
al,
> >> 2009), the PDR equation does not strictly apply and must be adjusted
> > because
> >> the stronger sperm also appears to benefit from the coupled formation,
> > which
> >> does not occur to any significant degree between coupled cyclists; i.e.
> > in a
> >> peloton the front riding cyclist does not receive any reduction in
output

> >> from the rider behind, while the rider behind benefits substantially by
> >> drafting; for bull sperm, it appears that both coupled sperm benefit by
> >> increased velocity.
> >>
> >> This leads to a further hypothesis that the stronger sperm increases
> > speed
> >> with some reduction in metabolic cost, while the weaker sperm increases
> >> speed with little or no change in metabolic cost, although they both
> > travel
> >> faster than they would individually.  Thus it is the stronger sperm

that
> >> benefits by energy savings, while the weaker sperm benefits by

increased

> >> speed, but with no savings in energy.  There is an implication that the
> >> stronger sperm will always be able to advance to the front of the sperm
> >> aggregation faster than weaker sperm.  However, this is not necessarily
> > so,
> >> as it depends on the relative durations of coupling and separations.
> > That
> >> is to say, a weaker sperm could advance farther and faster than a
> > stronger
> >> sperm if it spends sufficiently more time coupled than a stronger sperm
> >> which may spend relatively more time isolated.  Thus the faster sperm

are
> >> not necessarily those that are stronger, but those whose proportion of
> > total
> >> coupling time exceeds the percent differences in their relative fitness
> >> levels.
> >>
> >> The following model is descriptive for coupled organisms that may
> > alternate
> >> durations of time spent coupled with time spent non-coupled, and which
> >> mutually benefit from coupling because it accounts for the proportions

of
> >> total time spent both saving energy in coupled positions and not saving
> >> energy in non-coupled positions.  It is a simplified model because
there

> > are
> >> other factors that affect total output than time spent in energy-saving
> >> positions (coupled) and positions where there is no energy savings.
> >> However, it provides insight into the energetic dynamics of coupled
> > agents
> >> of varying degrees of fitness and why they do not necessarily achieve
> >> positions based on inherent fitness.
> >>
> >>
> >>
> >> TO = Wa-(Wa*%E) * T)  /  Wb-(Wb*%E) * T)
> >>
> >>
> >>
> >> ·         Where TO is ratio of total output of two agents in coupled
> >> positions (not necessarily with each other) with identical objective
> > (e.g.
> >> to win a race or impregnate an egg); here, sperm or cyclist; in the

case

> > of
> >> sperm, millijoules; for cyclists, calories
> >>
> >> ·         T is total time spent in coupled positions and travelling at
> >> mutually faster velocities than achievable in isolation
> >>
> >> ·         %E is percent energy savings in coupled formation
> >>
> >> ·         Wa is the maximum sustainable power output; picoNewtons for
> > sperm,
> >> watts for cyclists of stronger agent A (cyclist or sperm) at a given
> > moment
> >> , assuming that in a competitive situation, agents are travelling as

fast
> > as
> >> their metabolisms will allow.
> >>
> >> ·         Wb is the maximum sustainable power output at a given moment

of
> >> weaker agent B, again assuming that in a competitive situation, agents
> >> travel as fast as metabolisms will allow.
> >>
> >>
> >>
> >> For example (quantities and units for illustration only): if stronger
> > sperm
> >> A has max sustainable output of 50pN, and B has max sustainable output
of
> >> 45pN, and A saves an average of 10% output when coupled and spends a
> > total
> >> of 10 minutes coupled, total output for A is 50-5*10, or 450mj, while
the
> >> weaker sperm saves no energy when coupled, but spends 11 minutes in
> > coupled
> >> positions, we have 45-0*11, 495; and 450/495 = 0.91. Thus where this
> > ratio
> >> is <1, the weaker sperm potentially can be ahead of the stronger sperm
> > over
> >> the duration of the coupling interactions.  Thus this ratio indicates
why
> > it
> >> is not necessarily the case that stronger sperm will impregnate the
egg.

> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> ============================================================
> >> FRIAM Applied Complexity Group listserv
> >> Meets Fridays 9a-11:30 at cafe at St. John's College
> >> lectures, archives, unsubscribe, maps at http://www.friam.org
> >
> >
> >
> >
>
>
>

----------------------------------------------------------------------------

----
>
>
> > ============================================================
> > FRIAM Applied Complexity Group listserv
> > Meets Fridays 9a-11:30 at cafe at St. John's College
> > lectures, archives, unsubscribe, maps at http://www.friam.org
> >
>




============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Eric Charles]

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Nick Thompson]

YIKES!  Eric, please don't encourage anybody to read sarcasm into my message.  Absolutely none was intended. 

 

The question I am toying with,  is, does the model work without a "genefur" peletonizing?  If you see me leaning toward some conclusion, it would only be that if such a gene is lurking in the model, it could only be supported by Wilsonian group selection.  Hugh's model could be unpacked as a version of trait-group selection. 

 

But really I havent thought carefully enough about the model to be sarcastic, or enthusiastic, either. 

 

N

 

 

 

 

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email]; [hidden email]

Sent: 3/27/2010 3:54:23 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Hugh Trenchard]



Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Douglas Roberts-2]

Does anybody besides me have problems getting past the term "sperm pelotons"  without having bizarre mental images of teeny little bicycles, spandex, and colorful itty bitty jerseys?

--Doug

On Mon, Mar 29, 2010 at 9:42 AM, Hugh Trenchard <[hidden email]> wrote:

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert

role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 


Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>

> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>

> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of

fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small

enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the

slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 

> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the

riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally

coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of

riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions

where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within

the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts

among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 

> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the

peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>

> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as

cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing

of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 

> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,

but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 

say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!

>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 

> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh

>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Nick Thompson]

Hugh,

 

I yield to no man in my ignorance of subject we are talking about.  However, two points:

 

The term "genefur" is one I use to remind myself (and anyone who happens to be listening) that the common expression, "a gene for",  (as in "a gene for blue eyes" or "a gene for prostate cancer" is deeply problematic.  I should probably say something with more words, such as, "a gene for peletonizing, whatever the hell that might mean."   Although we know that the path from a trait in parents to the same trait in an offspring is much more tortured than a Dawkinsian argument requires, and that the material basis for parent-offspring is not as "atomic" as the expression "a gene for" implies, we continue to need a term for a unit of inheritance and "genefur" is a quietly ironic way to speak of units of inheritance while acknowledging that that sort of speech is silly. 

 

As I understand this discussion it has a lot to do with the group/individual selection argument.  Think of it this way.  Think of a bike race containing 20 riders from 5 teams.  Let it be the case that the winning  TEAM  takes down all the prize money but that it is shared unequally by members of the team, with half taken by the winning rider, a quarter by the second rider, and the an eighth by the 3rd rider, and the balance by the fourth, etc.  Now we have set up a conflict between group level and individual level success. 

 

My comments on fitness are only to remind us that "fitness" in a Darwinian conversation means winning the race by any means.  In your terms, "fitness" means using your resources to produce the maximum output.   Call these "fitnessD" and "fitnessT".  One could be "fitT" all by oneself on a stationary bike. However, as the scene in Breaking Away demonstrates, there are lots of way to be "fitD" without being "FitT". 

 

I wish we could engage David Sloan Wilson in this discussion, but he is too damned busy running around the world being famous and talking about the evolution of religion.  Gawd I hate when that happens. 

 

Nick

 

 

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email];[hidden email]

Cc: [hidden email]

Sent: 3/29/2010 9:42:09 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Nick Thompson]

Doug,

 

Clearly you have never looked closely at Sperm under a microscope. 

 

We have made enormous strides in micro-visualization technology in the last generation.

 

Nick

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Sent: 3/29/2010 9:48:32 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Does anybody besides me have problems getting past the term "sperm pelotons"  without having bizarre mental images of teeny little bicycles, spandex, and colorful itty bitty jerseys?

--Doug

On Mon, Mar 29, 2010 at 9:42 AM, Hugh Trenchard <[hidden email]> wrote:

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert

role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 


Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>

> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>

> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of

fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small

enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the

slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 

> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the

riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally

coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of

riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions

where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within

the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts

among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 

> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the

peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>

> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as

cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing

of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 

> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,

but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 

say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!

>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 

> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh

>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Roger Critchlow-2]

Hugh --

I like the analysis very much.  There should be other cases of velocity sorting in microbiology and perhaps in developmental biology, any place where cells are potentially crowded and need to get some where.

I think that sustainability for sperm is an oxymoron -- they have fixed food reserves and run until they succeed or starve.  Fitness is probably the wrong word, too, you can frame this in terms of individual and group efficiency:  the "peloton" goes further and gets anywhere sooner than any of its individuals could do by itself.  

So the doggerel version of the proposal would be able to start with:  "promiscuous peromyscus spermatozoa".

Perhaps Doug can get over his brightly colored spandex fixation and finish it for us?

-- rec --

On Mon, Mar 29, 2010 at 9:42 AM, Hugh Trenchard <[hidden email]> wrote:

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert

role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 


Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>

> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>

> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of

fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small

enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the

slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 

> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the

riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally

coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of

riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions

where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within

the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts

among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 

> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the

peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>

> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as

cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing

of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 

> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,

but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 

say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!

>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 

> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh

>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Douglas Roberts-2]

"promiscuous peromyscus spermatozoa cycles"

Nope, I'm afraid the fixation remains...

--Doug

On Mon, Mar 29, 2010 at 10:59 AM, Roger Critchlow <[hidden email]> wrote:

Hugh --

I like the analysis very much.  There should be other cases of velocity sorting in microbiology and perhaps in developmental biology, any place where cells are potentially crowded and need to get some where.

I think that sustainability for sperm is an oxymoron -- they have fixed food reserves and run until they succeed or starve.  Fitness is probably the wrong word, too, you can frame this in terms of individual and group efficiency:  the "peloton" goes further and gets anywhere sooner than any of its individuals could do by itself.  

So the doggerel version of the proposal would be able to start with:  "promiscuous peromyscus spermatozoa".

Perhaps Doug can get over his brightly colored spandex fixation and finish it for us?

-- rec --

On Mon, Mar 29, 2010 at 9:42 AM, Hugh Trenchard <[hidden email]> wrote:

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert


role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 



Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/


http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>


> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>


> Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of


fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small


enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the


slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 


> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the


riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally


coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of


riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions


where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within


the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace > oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts


among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 


> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the


peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>


> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as


cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing


of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 


> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,


but 
&g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 


say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!


>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 


> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>

> Hugh

>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Eric Charles]

But Nick,
Hugh's point is that we DO NOT need trait-group selection to explain the clustering sperm. We merely need sperm to swim in the same direction, AND have a variety of abilities. Given that alone, Hugh thinks he can prove, sperm will cluster based on their swimming abilities (which he calls 'fitness'). Thus I (captial 'I') declare that the real empirical question is whether or not sperm-in-clusters are more genetically similar than Hugh's model would predict. Only if THAT were true, would we conclude that group selection was involved, as the authors of the Nature article have claimed. That is, the authors of the Nature article have a flawed notion of what would happen by chance if sperm were swimming along without 'relatedness' detectors, and hence they have a flawed 'null hypothesis', and hence they have a flawed statistical test.

(This is all in the same sense that Schank's models have convincingly demonstrated that the results of so-called 'menstrual synchrony' research are exactly what you would expect due to chance. Those who think they showed 'menstrual synchrony' just have a flawed notion of what happens by chance.)

Eric




On Mon, Mar 29, 2010 12:30 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh,

 

I yield to no man in my ignorance of subject we are talking about.  However, two points:

 

The term "genefur" is one I use to remind myself (and anyone who happens to be listening) that the common expression, "a gene for",  (as in "a gene for blue eyes" or "a gene for prostate cancer" is deeply problematic.  I should probably say something with more words, such as, "a gene for peletonizing, whatever the hell that might mean."   Although we know that the path from a trait in parents to the same trait in an offspring is much more tortured than a Dawkinsian argument requires, and that the material basis for parent-offspring is not as "atomic" as the expression "a gene for" implies, we continue to need a term for a unit of inheritance and "genefur" is a quietly ironic way to speak of units of inheritance while acknowledging that that sort of speech is silly. 

 

As I understand this discussion it has a lot to do with the group/individual selection argument.  Think of it this way.  Think of a bike race containing 20 riders from 5 teams.  Let it be the case that the winning  TEAM  takes down all the prize money but that it is shared unequally by members of the team, with half taken by the winning rider, a quarter by the second rider, and the an eighth by the 3rd rider, and the balance by the fourth, etc.  Now we have set up a conflict between group level and individual level success. 

 

My comments on fitness are only to remind us that "fitness" in a Darwinian conversation means winning the race by any means.  In your terms, "fitness" means using your resources to produce the maximum output.   Call these "fitnessD" and "fitnessT".  One could be "fitT" all by oneself on a stationary bike. However, as the scene in Breaking Away demonstrates, there are lots of way to be "fitD" without being "FitT". 

 

I wish we could engage David Sloan Wilson in this discussion, but he is too damned busy running around the world being famous and talking about the evolution of religion.  Gawd I hate when that happens. 

 

Nick

 

 

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University (nthompson@...)

<a href="http://home.earthlink.net/%7Enickthompson/naturaldesigns/" onclick="window.open('http://home.earthlink.net/~nickthompson/naturaldesigns/');return false;">http://home.earthlink.net/~nickthompson/naturaldesigns/

<a href="http://www.cusf.org" onclick="window.open('http://www.cusf.org');return false;">http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: Hugh Trenchard

To: ERIC P. CHARLES;Nicholas Thompson

Cc: friam@...

Sent: 3/29/2010 9:42:09 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages! of ! energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: ERIC P. CHARLES

To: Nicholas Thompson

Cc: Hugh Trenchard ; friam@...

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: <a href="http://en.wikipedia.org/wiki/Flavor_text" onclick="window.open('http://en.wikipedia.org/wiki/Flavor_text');return false;">http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' orga! nism. To fix the flavor text of your model, you would need to explicitly recogni! ze that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we wo! uld expect the relatedness to be significantly larger that what our mo del predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
>!
  Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace 
> oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&a!
 mp;a!
 mp;g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Eric Charles

Professional Student and
Assistant Professor of Psychology
Penn State University
Altoona, PA 16601

============================================================
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[Steve Smith]

Nick -

Doug,

 

Clearly you have never looked closely at Sperm under a microscope.

That is not what his middle school science teacher told me!

- Steve


============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Douglas Roberts-2]

Gentlemen,

It was certainly not my intention to hijack this thread...

--Doug

On Mon, Mar 29, 2010 at 12:22 PM, Steve Smith <[hidden email]> wrote:

Nick -

Doug,

 

Clearly you have never looked closely at Sperm under a microscope.

That is not what his middle school science teacher told me!

- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Pamela McCorduck]

This man is a treasure. Yeah, you, Doug.

On Mar 29, 2010, at 2:30 PM, Douglas Roberts wrote:

Gentlemen,

It was certainly not my intention to hijack this thread...

--Doug

On Mon, Mar 29, 2010 at 12:22 PM, Steve Smith <[hidden email]> wrote:

Nick -

Doug,

 

Clearly you have never looked closely at Sperm under a microscope.

That is not what his middle school science teacher told me!

- Steve

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Vladimyr Burachynsky]

To Hugh and the peloton discussion group,

 

I did a little riding in spandex and have a small sense of the dynamics inside a peloton. I always thought it a marvelous experience while participating.

 

The most striking oddity for me about the discussion is the focus on the group concept. Personally it appears an artifact of the human propensity to organize random events into a pattern that may or may not have any meaning, it sounds a lot like an argument about what the shape of a cloud appears to represent. Each individual argues tautologically to support their specific perspective.

 

The way a peloton transforms over time exchanging members and breaking into subunits then reassembling seems to contradict any notion of group. A group definition dependent on time velocity or orientation is simply an instantaneous attribute and I think misleading.

 

Hugh’s model should display behaviors that surprise everyone simply because we are trapped by personal perspectives and expectations.  A peloton is a merciless entity disposing of riders as callously as wind strips leaves from trees in autumn. Yet occasionally it appears merciful, a weak rider can be hidden in the shadow and carried along until it has healed, its only function to tell jokes. Sprinters are typically delivered to the attack position in such a manner. Often the sprinter in tow is not even related to the mules. The mules or pullers try every tactic possible to rid themselves of the unwanted hanger on. So affinity is not a parameter for apparent cooperaton. That kind of blows the “Genefur” concept out of the water. To the outside observer cooperation seems dominant, to the rider it can be either a pleasant exercise or one filled with dread depending on how close is the finish line. Some pullers will invite a good joker along for the ride knowing full well that he will be dumped when things get serious. I personally have dumped riders who did not do their laundry regularly enough! Yes I pulled ahead and hit his front wheel, Not Nice I admit but he reeked and I could get away with it or so I thought. I had to confess to Friam, how peculiar!

 

The fixation with sorting based on speed, reserve energy etc. will lead to finding the best rationale to explain that idea. I just wish to insert a new dimension namely that the purpose of a peloton might be  to deliver sprinters. Energy optimization is not the goal but simply a tool. The peloton is an artifact of a few cyclists with temporarily synchronous goals.  The rewards in the peloton are human constructs, sprinters are evaluated by the trophy and pullers by delivering sprinters. The puller has only to select sprinters with the same logo as he wears, he forces the role of sprinter upon the one they identify as being the most explosive on that particular day. The pullers define the structure of the peloton and determine who becomes identified as a sprinter. The pullers are ruthless, and they rule the roost so to speak. Pullers can be absolute tyrants and discourage any individualism when they sense the target. They amuse themselves with little attacks at various stages to evaluate the strength of each little team. The sorting by velocity is a dangerously biased view of a peloton. It has some merit but underestimates or oversimplifies what might actually be happening.

 

Let me put it in another context, a peloton is one thing to outside observers and another to the individual riders, it is neither and perhaps it is both. The model that Hugh builds will be watched closely as Hugh seems to be onto something very important. Let the model speak for itself and later we will all argue about the wonderful patterns that appear in the “clouds”. Peloton strategy sessions following a race are intriguing since they typically have both a personal  and collective viewpoint. The personal is always the must relevant. Good team leaders play the riders like chess pieces and have no room for sentiment.

 

If Hugh has time to spare could you please let us lurkers know of some of your progress building the model. I am just getting started myself and am interested in “Group Dynamics” as artifacts of an external perspective.

 

I hope Hugh has an easier time understanding the peromyscus peloton  than was my experience with the local FOG ( Fast Old Guys) riders, I never made the grade!.

 

My guess towards building a group model of sperm is to program the agents as Tyranical Pullers willing to destroy themselves and everyone around themselves for a programmed goal, the program would be moderated by proximity to the goal. Perhaps they start off simply looking for a shadow behind a stronger rider, when the shadow is inconsistent they switch to a stronger lead wheel, there is no group selection just individual selection for an easy ride. The individual monitors his own energy state and tries to keep expenses at a minimum. He does also recognize is own affinity group based on some markers and attempts to keep them close (just how close is Hugh’s problem) In cycling it is possible to dispose of a follower by simply slowing your pace and letting your back wheel touch the following front wheel. Such dirty tricks are not uncommon. The follower almost always loses control. If not, he will return with a major attitude ! In this case the goal is not to win but to eliminate the opponents.  One has to be careful when doing this or the falling rider might take out a group of your affinity clan as well!  On the other hand this may be the function of some  sperm to eliminate competition from behind.

 

I will follow your progress Hugh, as you build your model , with  much enthusiasm.

 

I just pumped my skinny tires up and hope to do some lazy riding as spring arrives in Winnipeg.

 

 

Dr.Vladimyr Ivan Burachynsky

Ph.D.(Civil Eng.), M.Sc.(Mech.Eng.), M.Sc.(Biology)

 

120-1053 Beaverhill Blvd.

Winnipeg, Manitoba

CANADA R2J 3R2 

(204) 2548321  Phone/Fax

[hidden email] 

 

 

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Hugh Trenchard
Sent: March 29, 2010 10:42 AM
To: ERIC P. CHARLES; Nicholas Thompson
Cc: [hidden email]
Subject: Re: [FRIAM] Sperm pelotons; article in Nature

 

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

 

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 



Even if it has nothing to do with sperm it is a nifty model.  



There is an idea lurking here that i dont know whether it plays a covert

role in your thinking or not, but what about the fate of a "genefur"

peletonizing.  



My email program is misbehaving and my computer is about to crash so I wont

say more, now. 



 Nick 



Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology, 

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]









> [Original Message]

> From: Hugh Trenchard <[hidden email]>

> To: <[hidden email]>; The Friday Morning Applied

Complexity

Coffee Group <[hidden email]>

> Date: 3/27/2010 10:54:41 AM

> Subject: Re: [FRIAM] Sperm pelotons; article in Nature

>

> Thanks for taking a peek at my post. Great que!

 stions, and they help me to 

> see how/where my descriptions can be clarified.

>

> On the paradox part - that is one of the really interesting features of a 

> peloton: the energy savings effect of drafting narrows the range of

fitness 

> between the strongest and weakest riders.  In contrast, think of a pack

of 

> runners of varying fitness levels.  There is negligible drafting effect 

- 

> there is some, esp if running into a headwind, but overall it's small

enough 

> that it can be ignored for this illustration.  Say there are 50 runners,

all 

> separated incrementally by 1% difference in fitness; say they run a

couple 

> of miles. If they all start off slowly at say the max speed of the

slowest 

> runner, they can all run in a big group, separated only by enough

distance 

> between them to keep them from kicking and elbowing each other.  As they 

> pick up speed, the gr!

 oup thins into a line and are separated

incrementally 

&!

 gt; by d

istances that correspond to their differences in fitness.  In the

space 

> of two miles, they all finish individually in a single long line

according 

> to their fitness, and it can be predicted accurately where runners will 

> finish if you know their starting levels of fitness.

>

> This is not the case with a peloton.  For example at 25mph, riders can

save 

> at least 25% by drafting (approx savings 1%/mph) - all the

riders who are 

> within 25% fitness of the fastest rider can ride together even at the max 

> speed of the strongest rider.   So their fitness levels are effectively 

> narrowed, and they can all finish together as a group (ie. globally

coupled 

> by finishing within drafting range of each other), and so the

paradox. 

Part 

> of the paradox is also that, while fitness levels are effectively

narrowed 

> by drafting, it means, conversely, that a broader range of fitn!

 ess levels 

> can ride together in a group, which maybe isn't something that is clear

from 

> my initial post (though it is certainly implied).  Also, there

are other 

> important things going on in a peloton which precede the sorting of

riders 

> into groups, some of which I see I do need to clarify to make my model 

> clearer.

>

> Of these, particularly important are 1) the occurrence of peloton

rotations, 

> and 2) points of instability when riders are forced into positions

where 

> they do not have optimal drafting advantage. Below a certain output 

> threshold, when all drafting riders in a group are sufficiently below max 

> output, riders have sufficient energy to shift relative positions within

the 

> peloton, and in this particular phase, a self-organized rotational

pattern 

> forms whereby riders advance up the peripheries and riders are forced 

> backward down!

  the middle of the peloton. However, instabilities in pace > oc

cur along the way, caused by such things as course obstacles, hills

(when 

> lower speeds reduce drafting advantage, but when output may be at least

as 

> high), cross-winds, narrowing of the course, or short anaerobic bursts

among 

> riders at the front - all of which cause splits (i.e. PDR>1 at

these 

> points).   In a competitive situation, instabilities occur frequently 

> causing temporary splits at various places in the peloton, but these are 

> often closed when the cause of the instability has ceased.  Sorting thus 

> occurs according to some combination of peloton rotations in which

stronger 

> riders are able to get to the front and the continual splits in the

peloton 

> at points of instability and reintegrations. I would need to develop the 

> model some more to show this as an equation (though I touch on a

basic 

> version of it in my Appendix).

>

> For sperm, I!

  don't know what the initial state of the aggregates are when 

> they begin their travels, but I am assuming (perhaps quite

incorrectly), 

> that there is some initial phase in which they are mixed (such as

cyclists 

> on a starting line), and then they begin to sort as they increase

speed. 

> During the process, they aggregate like cyclists because a broader range

of 

> fitness levels can aggregate together (causing an effective narrowing

of 

> fitness). As in a peloton, there are  instabilities that allow for 

> continuous re-adjustments to the relative positions of all the sperm, and 

> over time they begin to sort into groups where each have fitness levels 

> closer to the average.  This is my hypothesis, at least.

>

> On the second last question, there would be an advantage to sperm among

the 

> first pulse aggregation if all the pulsed aggregations do not mix first,

but 

&g!

 t; the principles apply to each aggregation.  However, I don't!

  know wh

ether 

> there is some other process of mixing first among all the pulses of sperm 

> aggregations before they begin traveling (I imagine I could find the

answer 

> in the literature), in which case there could easily be a sperm in, 

say, 

> the second pulse, which could end up impregnating the egg.

>

> I don't know about the kamikaze sperm - I'll leave that one for now!  But

I 

> do remember that scene from the movie as clear as day!

>

> In any event, my aim is really to ask the question - are there energetic

and 

> coupling principles that allow sperm to end up in groups which otherwise 

> appear to have occurred because genetically related sperm can somehow 

> identify each other?   I am really only suggesting the existence of some 

> dynamics of the sperm aggregations that could be studied for, which don't 

> yet appear to have been addressed.

>

> Hugh

>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Nick Thompson]

Eric,

 

That much I figured out.  I need to know more about the structure of cycle races.  I thought it was the case that races contained teams and that the team that produced a winning rider won the race, even if all the other team members died in the effort.  Not true?

 

if it IS true than group effects are obviously relevant,

 

N

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email]; [hidden email]

Sent: 3/29/2010 11:13:31 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

But Nick,
Hugh's point is that we DO NOT need trait-group selection to explain the clustering sperm. We merely need sperm to swim in the same direction, AND have a variety of abilities. Given that alone, Hugh thinks he can prove, sperm will cluster based on their swimming abilities (which he calls 'fitness'). Thus I (captial 'I') declare that the real empirical question is whether or not sperm-in-clusters are more genetically similar than Hugh's model would predict. Only if THAT were true, would we conclude that group selection was involved, as the authors of the Nature article have claimed. That is, the authors of the Nature article have a flawed notion of what would happen by chance if sperm were swimming along without 'relatedness' detectors, and hence they have a flawed 'null hypothesis', and hence they have a flawed statistical test.

(This is all in the same sense that Schank's models have convincingly demonstrated that the results of so-called 'menstrual synchrony' research are exactly what you would expect due to chance. Those who think they showed 'menstrual synchrony' just have a flawed notion of what happens by chance.)

Eric




On Mon, Mar 29, 2010 12:30 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh,

 

I yield to no man in my ignorance of subject we are talking about.  However, two points:

 

The term "genefur" is one I use to remind myself (and anyone who happens to be listening) that the common expression, "a gene for",  (as in "a gene for blue eyes" or "a gene for prostate cancer" is deeply problematic.  I should probably say something with more words, such as, "a gene for peletonizing, whatever the hell that might mean."   Although we know that the path from a trait in parents to the same trait in an offspring is much more tortured than a Dawkinsian argument requires, and that the material basis for parent-offspring is not as "atomic" as the expression "a gene for" implies, we continue to need a term for a unit of inheritance and "genefur" is a quietly ironic way to speak of units of inheritance while acknowledging that that sort of speech is silly. 

 

As I understand this discussion it has a lot to do with the group/individual selection argument.  Think of it this way.  Think of a bike race containing 20 riders from 5 teams.  Let it be the case that the winning  TEAM  takes down all the prize money but that it is shared unequally by members of the team, with half taken by the winning rider, a quarter by the second rider, and the an eighth by the 3rd rider, and the balance by the fourth, etc.  Now we have set up a conflict between group level and individual level success. 

 

My comments on fitness are only to remind us that "fitness" in a Darwinian conversation means winning the race by any means.  In your terms, "fitness" means using your resources to produce the maximum output.   Call these "fitnessD" and "fitnessT".  One could be "fitT" all by oneself on a stationary bike. However, as the scene in Breaking Away demonstrates, there are lots of way to be "fitD" without being "FitT". 

 

I wish we could engage David Sloan Wilson in this discussion, but he is too damned busy running around the world being famous and talking about the evolution of religion.  Gawd I hate when that happens. 

 

Nick

 

 

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University (nthompson@...)

<A onclick="window.open('http://home.earthlink.net/~nickthompson/naturaldesigns/');return false;" href="http://home.earthlink.net/%7Enickthompson/naturaldesigns/">http://home.earthlink.net/~nickthompson/naturaldesigns/

<A onclick="window.open('http://www.cusf.org');return false;" href="http://www.cusf.org">http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: Hugh Trenchard

To: ERIC P. CHARLES;Nicholas Thompson

Cc: friam@...

Sent: 3/29/2010 9:42:09 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages! of ! energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: ERIC P. CHARLES

To: Nicholas Thompson

Cc: Hugh Trenchard ; friam@...

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: <A onclick="window.open('http://en.wikipedia.org/wiki/Flavor_text');return false;" href="http://en.wikipedia.org/wiki/Flavor_text">http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' orga! nism. To fix the flavor text of your model, you would need to explicitly recogni! ze that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we wo! uld expect the relatedness to be significantly larger that what our mo del predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
>!
  Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace 
> oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&a!
 mp;a!
 mp;g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Eric Charles

Professional Student and
Assistant Professor of Psychology
Penn State University
Altoona, PA 16601

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Hugh Trenchard]



Thanks, Eric.  That puts it nice and succinctly. That said, I take the points about how best to characterize "fitness" and will adjust my draft accordingly (and I had some chuckles over the lighter responses too). I'll revise it and re-send it sometime over the next few days (it might be old news by then, but at least it motivates me to keep working on it!).  I've just seen Vladimir Burachynsky's post, and will respond to that momentarily too.

 

Hugh

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Monday, March 29, 2010 10:13 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

But Nick,
Hugh's point is that we DO NOT need trait-group selection to explain the clustering sperm. We merely need sperm to swim in the same direction, AND have a variety of abilities. Given that alone, Hugh thinks he can prove, sperm will cluster based on their swimming abilities (which he calls 'fitness'). Thus I (captial 'I') declare that the real empirical question is whether or not sperm-in-clusters are more genetically similar than Hugh's model would predict. Only if THAT were true, would we conclude that group selection was involved, as the authors of the Nature article have claimed. That is, the authors of the Nature article have a flawed notion of what would happen by chance if sperm were swimming along without 'relatedness' detectors, and hence they have a flawed 'null hypothesis', and hence they have a flawed statistical test.

(This is all in the same sense that Schank's models have convincingly demonstrated that the results of so-called 'menstrual synchrony' research are exactly what you would expect due to chance. Those who think they showed 'menstrual synchrony' just have a flawed notion of what happens by chance.)

Eric




On Mon, Mar 29, 2010 12:30 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh,

 

I yield to no man in my ignorance of subject we are talking about.  However, two points:

 

The term "genefur" is one I use to remind myself (and anyone who happens to be listening) that the common expression, "a gene for",  (as in "a gene for blue eyes" or "a gene for prostate cancer" is deeply problematic.  I should probably say something with more words, such as, "a gene for peletonizing, whatever the hell that might mean."   Although we know that the path from a trait in parents to the same trait in an offspring is much more tortured than a Dawkinsian argument requires, and that the material basis for parent-offspring is not as "atomic" as the expression "a gene for" implies, we continue to need a term for a unit of inheritance and "genefur" is a quietly ironic way to speak of units of inheritance while acknowledging that that sort of speech is silly. 

 

As I understand this discussion it has a lot to do with the group/individual selection argument.  Think of it this way.  Think of a bike race containing 20 riders from 5 teams.  Let it be the case that the winning  TEAM  takes down all the prize money but that it is shared unequally by members of the team, with half taken by the winning rider, a quarter by the second rider, and the an eighth by the 3rd rider, and the balance by the fourth, etc.  Now we have set up a conflict between group level and individual level success. 

 

My comments on fitness are only to remind us that "fitness" in a Darwinian conversation means winning the race by any means.  In your terms, "fitness" means using your resources to produce the maximum output.   Call these "fitnessD" and "fitnessT".  One could be "fitT" all by oneself on a stationary bike. However, as the scene in Breaking Away demonstrates, there are lots of way to be "fitD" without being "FitT". 

 

I wish we could engage David Sloan Wilson in this discussion, but he is too damned busy running around the world being famous and talking about the evolution of religion.  Gawd I hate when that happens. 

 

Nick

 

 

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology,

Clark University (nthompson@...)

<A onclick="window.open('http://home.earthlink.net/~nickthompson/naturaldesigns/');return false;" href="http://home.earthlink.net/%7Enickthompson/naturaldesigns/">http://home.earthlink.net/~nickthompson/naturaldesigns/

<A onclick="window.open('http://www.cusf.org');return false;" href="http://www.cusf.org">http://www.cusf.org [City University of Santa Fe]

 

 

 

 

----- Original Message -----

From: Hugh Trenchard

To: ERIC P. CHARLES;Nicholas Thompson

Cc: friam@...

Sent: 3/29/2010 9:42:09 AM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages! of ! energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: ERIC P. CHARLES

To: Nicholas Thompson

Cc: Hugh Trenchard ; friam@...

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: <A onclick="window.open('http://en.wikipedia.org/wiki/Flavor_text');return false;" href="http://en.wikipedia.org/wiki/Flavor_text">http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' orga! nism. To fix the flavor text of your model, you would need to explicitly recogni! ze that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we wo! uld expect the relatedness to be significantly larger that what our mo del predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 

Even if it has nothing to do with sperm it is a nifty model.  

There is an idea lurking here that i dont know whether it plays a covert
role in your thinking or not, but what about the fate of a "genefur"
peletonizing.  

My email program is misbehaving and my computer is about to crash so I wont
say more, now. 

 Nick 

Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University ([hidden email])
http://home.earthlink.net/~nickthompson/naturaldesigns/
http://www.cusf.org [City University of Santa Fe]




> [Original Message]
> From: Hugh Trenchard <[hidden email]>
> To: <[hidden email]>; The Friday Morning Applied
Complexity
Coffee Group <[hidden email]>
>!
  Date: 3/27/2010 10:54:41 AM
> Subject: Re: [FRIAM] Sperm pelotons; article in Nature
>
> Thanks for taking a peek at my post. Great que!
 stions, and they help me to 
> see how/where my descriptions can be clarified.
>
> On the paradox part - that is one of the really interesting features of a 
> peloton: the energy savings effect of drafting narrows the range of
fitness 
> between the strongest and weakest riders.  In contrast, think of a pack
of 
> runners of varying fitness levels.  There is negligible drafting effect 
- 
> there is some, esp if running into a headwind, but overall it's small
enough 
> that it can be ignored for this illustration.  Say there are 50 runners,
all 
> separated incrementally by 1% difference in fitness; say they run a
couple 
> of miles. If they all start off slowly at say the max speed of the
slowest 
> runner, they can all run in a big group, separated only by enough
distance 
> between them to keep them from kicking and elbowing each other.  As they 
> pick up speed, the gr!
 oup thins into a line and are separated
incrementally 
&!
 gt; by d
istances that correspond to their differences in fitness.  In the
space 
> of two miles, they all finish individually in a single long line
according 
> to their fitness, and it can be predicted accurately where runners will 
> finish if you know their starting levels of fitness.
>
> This is not the case with a peloton.  For example at 25mph, riders can
save 
> at least 25% by drafting (approx savings 1%/mph) - all the
riders who are 
> within 25% fitness of the fastest rider can ride together even at the max 
> speed of the strongest rider.   So their fitness levels are effectively 
> narrowed, and they can all finish together as a group (ie. globally
coupled 
> by finishing within drafting range of each other), and so the
paradox. 
Part 
> of the paradox is also that, while fitness levels are effectively
narrowed 
> by drafting, it means, conversely, that a broader range of fitn!
 ess levels 
> can ride together in a group, which maybe isn't something that is clear
from 
> my initial post (though it is certainly implied).  Also, there
are other 
> important things going on in a peloton which precede the sorting of
riders 
> into groups, some of which I see I do need to clarify to make my model 
> clearer.
>
> Of these, particularly important are 1) the occurrence of peloton
rotations, 
> and 2) points of instability when riders are forced into positions
where 
> they do not have optimal drafting advantage. Below a certain output 
> threshold, when all drafting riders in a group are sufficiently below max 
> output, riders have sufficient energy to shift relative positions within
the 
> peloton, and in this particular phase, a self-organized rotational
pattern 
> forms whereby riders advance up the peripheries and riders are forced 
> backward down!
  the middle of the peloton. However, instabilities in pace 
> oc
cur along the way, caused by such things as course obstacles, hills
(when 
> lower speeds reduce drafting advantage, but when output may be at least
as 
> high), cross-winds, narrowing of the course, or short anaerobic bursts
among 
> riders at the front - all of which cause splits (i.e. PDR>1 at
these 
> points).   In a competitive situation, instabilities occur frequently 
> causing temporary splits at various places in the peloton, but these are 
> often closed when the cause of the instability has ceased.  Sorting thus 
> occurs according to some combination of peloton rotations in which
stronger 
> riders are able to get to the front and the continual splits in the
peloton 
> at points of instability and reintegrations. I would need to develop the 
> model some more to show this as an equation (though I touch on a
basic 
> version of it in my Appendix).
>
> For sperm, I!
  don't know what the initial state of the aggregates are when 
> they begin their travels, but I am assuming (perhaps quite
incorrectly), 
> that there is some initial phase in which they are mixed (such as
cyclists 
> on a starting line), and then they begin to sort as they increase
speed. 
> During the process, they aggregate like cyclists because a broader range
of 
> fitness levels can aggregate together (causing an effective narrowing
of 
> fitness). As in a peloton, there are  instabilities that allow for 
> continuous re-adjustments to the relative positions of all the sperm, and 
> over time they begin to sort into groups where each have fitness levels 
> closer to the average.  This is my hypothesis, at least.
>
> On the second last question, there would be an advantage to sperm among
the 
> first pulse aggregation if all the pulsed aggregations do not mix first,
but 
&a!
 mp;a!
 mp;g!
 t; the principles apply to each aggregation.  However, I don't!
  know wh
ether 
> there is some other process of mixing first among all the pulses of sperm 
> aggregations before they begin traveling (I imagine I could find the
answer 
> in the literature), in which case there could easily be a sperm in, 
say, 
> the second pulse, which could end up impregnating the egg.
>
> I don't know about the kamikaze sperm - I'll leave that one for now!  But
I 
> do remember that scene from the movie as clear as day!
>
> In any event, my aim is really to ask the question - are there energetic
and 
> coupling principles that allow sperm to end up in groups which otherwise 
> appear to have occurred because genetically related sperm can somehow 
> identify each other?   I am really only suggesting the existence of some 
> dynamics of the sperm aggregations that could be studied for, which don't 
> yet appear to have been addressed.
>
> Hugh
>

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

Eric Charles

Professional Student and
Assistant Professor of Psychology
Penn State University
Altoona, PA 16601

============================================================
FRIAM Applied Complexity Group listserv
Meets Fridays 9a-11:30 at cafe at St. John's College
lectures, archives, unsubscribe, maps at http://www.friam.org

[Douglas Roberts-2]

Hi, Vladimyr,

I've also ridden in pelotons on multi-day longish rides.  In spandex.  

On those longish 10+ hour per day rides, the pelotons do indeed form, fragment, and then re-form throughout the ride.  One element of a functioning peloton that I doubt our teensy counterparts would exhibit is the structured rotation of the head of the pack.  As the lead rider tires, he (or they in a 2-abreast pack) peel off and then fall in again at the rear of the pack.  That way a peloton can maintain a speed a good 20% above what a single rider could maintain for considerable distances.

I have to confess, however, that frequently I found myself riding in the shadow of the stronger, faster members of the pack.  Telling jokes.  However, as much as they might have desired, they (like FRIAM) found it was usually more difficult than they might have expected to leave me in the dust.

BTW, for a real thrill you should hitch your wagon to a fast tandom pack just as it crests the pass on day two of the TOSRV West tour, heading down the long, steep stretch to Flathead Lake in Montana.  Tears and snot flying off the riders in the brisk morning air of the Bitterroot Mountains as the speeds approach 60 MPH.  No sperm, though.

--Doug

On Mon, Mar 29, 2010 at 4:30 PM, Vladimyr Ivan Burachynsky <[hidden email]> wrote:

To Hugh and the peloton discussion group,

 

I did a little riding in spandex and have a small sense of the dynamics inside a peloton. I always thought it a marvelous experience while participating.

 

The most striking oddity for me about the discussion is the focus on the group concept. Personally it appears an artifact of the human propensity to organize random events into a pattern that may or may not have any meaning, it sounds a lot like an argument about what the shape of a cloud appears to represent. Each individual argues tautologically to support their specific perspective.

 

The way a peloton transforms over time exchanging members and breaking into subunits then reassembling seems to contradict any notion of group. A group definition dependent on time velocity or orientation is simply an instantaneous attribute and I think misleading.

 

Hugh’s model should display behaviors that surprise everyone simply because we are trapped by personal perspectives and expectations.  A peloton is a merciless entity disposing of riders as callously as wind strips leaves from trees in autumn. Yet occasionally it appears merciful, a weak rider can be hidden in the shadow and carried along until it has healed, its only function to tell jokes. Sprinters are typically delivered to the attack position in such a manner. Often the sprinter in tow is not even related to the mules. The mules or pullers try every tactic possible to rid themselves of the unwanted hanger on. So affinity is not a parameter for apparent cooperaton. That kind of blows the “Genefur” concept out of the water. To the outside observer cooperation seems dominant, to the rider it can be either a pleasant exercise or one filled with dread depending on how close is the finish line. Some pullers will invite a good joker along for the ride knowing full well that he will be dumped when things get serious. I personally have dumped riders who did not do their laundry regularly enough! Yes I pulled ahead and hit his front wheel, Not Nice I admit but he reeked and I could get away with it or so I thought. I had to confess to Friam, how peculiar!

 

The fixation with sorting based on speed, reserve energy etc. will lead to finding the best rationale to explain that idea. I just wish to insert a new dimension namely that the purpose of a peloton might be  to deliver sprinters. Energy optimization is not the goal but simply a tool. The peloton is an artifact of a few cyclists with temporarily synchronous goals.  The rewards in the peloton are human constructs, sprinters are evaluated by the trophy and pullers by delivering sprinters. The puller has only to select sprinters with the same logo as he wears, he forces the role of sprinter upon the one they identify as being the most explosive on that particular day. The pullers define the structure of the peloton and determine who becomes identified as a sprinter. The pullers are ruthless, and they rule the roost so to speak. Pullers can be absolute tyrants and discourage any individualism when they sense the target. They amuse themselves with little attacks at various stages to evaluate the strength of each little team. The sorting by velocity is a dangerously biased view of a peloton. It has some merit but underestimates or oversimplifies what might actually be happening.

 

Let me put it in another context, a peloton is one thing to outside observers and another to the individual riders, it is neither and perhaps it is both. The model that Hugh builds will be watched closely as Hugh seems to be onto something very important. Let the model speak for itself and later we will all argue about the wonderful patterns that appear in the “clouds”. Peloton strategy sessions following a race are intriguing since they typically have both a personal  and collective viewpoint. The personal is always the must relevant. Good team leaders play the riders like chess pieces and have no room for sentiment.

 

If Hugh has time to spare could you please let us lurkers know of some of your progress building the model. I am just getting started myself and am interested in “Group Dynamics” as artifacts of an external perspective.

 

I hope Hugh has an easier time understanding the peromyscus peloton  than was my experience with the local FOG ( Fast Old Guys) riders, I never made the grade!.

 

My guess towards building a group model of sperm is to program the agents as Tyranical Pullers willing to destroy themselves and everyone around themselves for a programmed goal, the program would be moderated by proximity to the goal. Perhaps they start off simply looking for a shadow behind a stronger rider, when the shadow is inconsistent they switch to a stronger lead wheel, there is no group selection just individual selection for an easy ride. The individual monitors his own energy state and tries to keep expenses at a minimum. He does also recognize is own affinity group based on some markers and attempts to keep them close (just how close is Hugh’s problem) In cycling it is possible to dispose of a follower by simply slowing your pace and letting your back wheel touch the following front wheel. Such dirty tricks are not uncommon. The follower almost always loses control. If not, he will return with a major attitude ! In this case the goal is not to win but to eliminate the opponents.  One has to be careful when doing this or the falling rider might take out a group of your affinity clan as well!  On the other hand this may be the function of some  sperm to eliminate competition from behind.

 

I will follow your progress Hugh, as you build your model , with  much enthusiasm.

 

I just pumped my skinny tires up and hope to do some lazy riding as spring arrives in Winnipeg.

 

 

Dr.Vladimyr Ivan Burachynsky

Ph.D.(Civil Eng.), M.Sc.(Mech.Eng.), M.Sc.(Biology)

 

120-1053 Beaverhill Blvd.

Winnipeg, Manitoba

CANADA R2J 3R2 

(204) 2548321  Phone/Fax

[hidden email] 

 

 

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Hugh Trenchard
Sent: March 29, 2010 10:42 AM
To: ERIC P. CHARLES; Nicholas Thompson
Cc: [hidden email]

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

 

Thanks Eric for taking the time to look through my post.  For Nick's last post, I am not entirely sure what a "genefur" is, although it sounds like it is a reference to an inherent genetic trait, as you also discuss.

 

Yes, I agree it will help my argument if I hone in more closely on what I mean by fitness, and I will add some description to clarify this. My useage relates to inherent physical fitness in terms of maximum power output capacity. That too needs fine-tuning because I refer to "maximum sustainable output", which is not the same as absolute maximum power output, and I would need to outline more carefully what this means.  Regardless, I  think there are ways of testing for the actual power-output capacities of individual sperm - I have seen references in the literature to testing procedures for this.

 

Because I know very little about genetics, for my part I would be treading dangerously to begin describing the process in a gene-related sense (and I would not want to get into discussion about chromosomes), but to address the issue you raise (if I understand it correctly), it would be necessary to measure the power output of the sperm of individual male mice to determine the range of their output capacities and/or the sperms' average output. This is no doubt not easy, but I imagine there would be some sampling size that would provide an accurate indication of the overall output range. And certainly one would want clearly to correspond average sperm outputs and ranges with the genetic descriptions of the various mice tested, but this could be done according to a replication of the Fisher and Hoesktra procedures.  It would also be necessary to determine percentages of energy savings that occur when sperm are coupled (if this does in fact occur).

 

My model assumes that there is a difference in the average power output of individual males' sperm, whether related or unrelated or of the same species or not - a difference sufficiently significant to demonstrate that sorting occurs according to fitness (in the power-output sense) and not according to some mechanism for identifying the genetic relatedness of the sperm, as the authors of the Nature article appear to suggest.  The fact that sperm aggregate indicates coupling and energy savings, which is why (in my view) the peloton model applies.

 

In terms of chance, it seems to me Fisher and Hoekstra have taken a lot of care to establish that there is sorting beyond chance, but implicitly ascribe that sorting to some sensory/perceptual capacity of the sperm to identify related sperm.  My model begins with their proven result that there is sorting beyond chance, and asks whether there is some sorting mechanism involved other than an unidentified mechanism to perceive the location of related sperm, which is intuitively problematic because (it seems) sperm do not have a sufficiently developed sensory system (i.e. eyes, ears, or other) to do this.

 

My model provides a simpler explanation for the sorting process than the Hoekstra & Fisher explanation, because, in my model, sorting occurs according to self-organized energetic principles, and not according to a perceptual/sensory mechanism, as apparently implied by the authors. 

 

I can see how a basic computer simulation would be helpful as a starting point for making predictions according to my model, which I see is really my next step. 

 

Does anyone know how/where one could apply for some funding to resource such a simulation?  I could develop it myself (and have developed at least one simulation, but it really needs to be worked through again), but it would happen a whole lot faster if I could engage someone more adept at computer modelling than me.

 

 

----- Original Message -----

From: [hidden email]

To: [hidden email]

Cc: [hidden email] ; [hidden email]

Sent: Saturday, March 27, 2010 2:54 PM

Subject: Re: [FRIAM] Sperm pelotons; article in Nature

 

Hugh,
Very interesting model! One of my doctoral adviser's, Jeffrey Schank has demonstrated repeatedly that scientists are very bad at predicting what 'chance' looks like when trying to do experiments involving synchrony. This seems one of those situations, and the only way around it is modeling.

Nick's sarcasm aside, he has a point, and it has to do with some of the flavor text surrounding your model (for geeks of the wrong variety to know what flavor text is, see: http://en.wikipedia.org/wiki/Flavor_text). If I can take a shot at identifying the problem:

Rather than looking at 'fitness' as if it were a unified trait, you have created a model that needs some mutli-stage selection language (the better term escapes me at the moment). The reality is that what makes a 'fit' sperm is not necessarily what makes a 'fit' organism. To fix the flavor text of your model, you would need to explicitly recognize that (if the sperm sort, then) the sperm are going to sort based on a similarity in the genes that 'build' the sperm. Their sorting will be completely independent of all the other genes, or of any role that the sperm-building genes might later play as body-building genes. Ignoring chromosomal linkages (which you shouldn't), two sperm could be identical on all the genes important for building sperm, but completely different in terms of all other genes.

Your model would thus al! low a much clearer test of the prediction that sperm identify each other in some way. It does so because it provides a vastly improved predicted relatedness due to chance. GIVEN: We would expect sperm to cluster along the race track based on the similarity of certain, specifiable genes. MODEL: If we know the genes important for building sperm, we can model the expected relatedness of sperms within a cluster. IF: Sperm are implementing some weird sort of kin selection mechanism - THEN: we would expect the relatedness to be significantly larger that what our model predicts.

Any help?

Eric


On Sat, Mar 27, 2010 01:36 PM, "Nicholas Thompson" <[hidden email]> wrote:

Hugh, 



Even if it has nothing to do with sperm it is a nifty model.  



There is an idea lurking here that i dont know whether it plays a covert

role in your thinking or not, but what about the fate of a "genefur"

peletonizing.  



My email program is misbehaving and my computer is about to crash so I wont

say more, now. 



 Nick 



Nicholas S. Thompson

Emeritus Professor of Psychology and Ethology, 

Clark University ([hidden email])

http://home.earthlink.net/~nickthompson/naturaldesigns/

http://www.cusf.org [City University of Santa Fe]









> [Original Message]

> From: Hugh Trenchard <[hidden email]>

> To: <[hidden email]>; The Friday Morning Applied

Complexity

Coffee Group <[hidden email]>

> Date: 3/27/2010 10:54:41 AM

> Subject: Re: [FRIAM] Sperm pelotons; article in Nature

>

> Thanks for taking a peek at my post. Great que!

 stions, and they help me to 

> see how/where my descriptions can be clarified.

>

> On the paradox part - that is one of the really interesting features of a 

> peloton: the energy savings effect of drafting narrows the range of

fitness 

> between the strongest and weakest riders.  In contrast, think of a pack

of 

> runners of varying fitness levels.  There is negligible drafting effect 

- 

> there is some, esp if running into a headwind, but overall it's small

enough 

> that it can be ignored for this illustration.  Say there are 50 runners,

all 

> separated incrementally by 1% difference in fitness; say they run a

couple 

> of miles. If they all start off slowly at say the max speed of the

slowest 

> runner, they can all run in a big group, separated only by enough

distance 

> between them to keep them from kicking and elbowing each other.  As they 

> pick up speed, the gr!

 oup thins into a line and are separated

incrementally 

&!

 gt; by d

istances that correspond to their differences in fitness.  In the


space 

> of two miles, they all finish individually in a single long line

according 

> to their fitness, and it can be predicted accurately where runners will 

> finish if you know their starting levels of fitness.

>

> This is not the case with a peloton.  For example at 25mph, riders can

save 

> at least 25% by drafting (approx savings 1%/mph) - all the

riders who are 

> within 25% fitness of the fastest rider can ride together even at the max 

> speed of the strongest rider.   So their fitness levels are effectively 

> narrowed, and they can all finish together as a group (ie. globally

coupled 

> by finishing within drafting range of each other), and so the

paradox. 

Part 

> of the paradox is also that, while fitness levels are effectively

narrowed 

> by drafting, it means, conversely, that a broader range of fitn!

 ess levels 

> can ride together in a group, which maybe isn't something that is clear

from 

> my initial post (though it is certainly implied).  Also, there

are other 

> important things going on in a peloton which precede the sorting of

riders 

> into groups, some of which I see I do need to clarify to make my model 

> clearer.

>

> Of these, particularly important are 1) the occurrence of peloton

rotations, 

> and 2) points of instability when riders are forced into positions

where 

> they do not have optimal drafting advantage. Below a certain output 

> threshold, when all drafting riders in a group are sufficiently below max 

> output, riders have sufficient energy to shift relative positions within

the 

> peloton, and in this particular phase, a self-organized rotational

pattern 

> forms whereby riders advance up the peripheries and riders are forced 

> backward down!

  the middle of the peloton. However, instabilities in pace > oc

cur along the way, caused by such things as course obstacles, hills

(when 

> lower speeds reduce drafting advantage, but when output may be at least

as 

> high), cross-winds, narrowing of the course, or short anaerobic bursts

among 

> riders at the front - all of which cause splits (i.e. PDR>1 at

these 

> points).   In a competitive situation, instabilities occur frequently 

> causing temporary splits at various places in the peloton, but these are 

> often closed when the cause of the instability has ceased.  Sorting thus 

> occurs according to some combination of peloton rotations in which

stronger 

> riders are able to get to the front and the continual splits in the

peloton 

> at points of instability and reintegrations. I would need to develop the 

> model some more to show this as an equation (though I touch on a

basic 

> version of it in my Appendix).

>

> For sperm, I!

  don't know what the initial state of the aggregates are when 

> they begin their travels, but I am assuming (perhaps quite

incorrectly), 

> that there is some initial phase in which they are mixed (such as

cyclists 

> on a starting line), and then they begin to sort as they increase

speed. 

> During the process, they aggregate like cyclists because a broader range

of 

> fitness levels can aggregate together (causing an effective narrowing

of 

> fitness). As in a peloton, there are  instabilities that allow for 

> continuous re-adjustments to the relative positions of all the sperm, and 

> over time they begin to sort into groups where each have fitness levels 

> closer to the average.  This is my hypothesis, at least.

>

> On the second last question, there would be an advantage to sperm among

the 

> first pulse aggregation if all the pulsed aggregations do not mix first,

but 

&g!

 t; the principles apply to each aggregation.  However, I don't!

  know wh

ether 

> there is some other process of mixing first among all the pulses of sperm 

> aggregations before they begin traveling (I imagine I could find the

answer 

> in the literature), in which case there could easily be a sperm in, 

say, 

> the second pulse, which could end up impregnating the egg.

>

> I don't know about the kamikaze sperm - I'll leave that one for now!  But

I 

> do remember that scene from the movie as clear as day!

>

> In any event, my aim is really to ask the question - are there energetic

and 

> coupling principles that allow sperm to end up in groups which otherwise 

> appear to have occurred because genetically related sperm can somehow 

> identify each other?   I am really only suggesting the existence of some 

> dynamics of the sperm aggregations that could be studied for, which don't 

> yet appear to have been addressed.

>

> Hugh

>

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