"promiscuous peromyscus spermatozoa cycles" Nope, I'm afraid the fixation remains...
--Doug On Mon, Mar 29, 2010 at 10:59 AM, Roger Critchlow <r...@elf.org> 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 <htrench...@shaw.ca>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:* ERIC P. CHARLES <e...@psu.edu> >> *To:* Nicholas Thompson <nickthomp...@earthlink.net> >> *Cc:* Hugh Trenchard <htrench...@shaw.ca> ; friam@redfish.com >> *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" < >> nickthomp...@earthlink.net>* 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 (nthomp...@clarku.edu) >> http://home.earthlink.net/~nickthompson/naturaldesigns/ >> http://www.cusf.org [City University of Santa Fe] >> >> >> >> >> > [Original Message] >> > From: Hugh Trenchard <htrench...@shaw.ca> >> >> > To: <nickthomp...@earthlink.net>; The Friday Morning Applied >> Complexity >> Coffee Group <friam@redfish.com> >> >> > 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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