Bromance: Sperm Heads Cluster to Get Ahead.

Bromance: Sperm Heads Cluster to Get Ahead. In the race towards fertilization, speed matters. And you thought it was size? Researchers found that sperm of many mammals, including the deer mouse Peromyscus, come supplied with hooks so they can literally put their heads together (see image) and swim faster (127.4 μm s−1 ± 3.8 s.e.m. versus 109.8 μm s−1 ± 3.7 s.e.m.). In rats (Rattus norvegicus) for example, ‘trains’ of up to hundreds of sperm link up and boogie together. Yet, only one sperm can fertilize the egg. There is also a hidden danger to this altruism: contact could accidentally trigger the “acrosome” reaction prematurely, and take the sperm out of running altogether. So why do sperm indulge in this risky behavior?

Polygamy Rules: Did you know that 95% of all mammals are promiscuous? Humans (mostly!) fall in the 5% minority. It is scandalous but true that the female mouse P. maniculatus will mate with successive males as quickly as one minute apart. Scientists reasoned that sperm clustering within a species or within individual males could give a selective evolutionary advantage. They tested this by labeling sperm from different sources red or green. As seen in the image, kinship prevails: so, sperm of a feather flock together. This distinction was even seen between sperm from siblings! Boringly, human sperm do not cluster.

It’s in your jeans genes: Given that social amoebae like Dictyostelium can aggregate, scientists believe that simple genetics underlie this interesting behavior.  New research shows that genetic differences in the immune system distinguish promiscuous species of mice from closely related monogamous species. Other social behavior, that make some animals loners while others to live in groups, is now being studied. Read more: http://goo.gl/kt1Tg

REF: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2824558/#SD1

Video: NPR Science: Sperm Of A Feather Flock Together

#sciencesunday ScienceSunday 

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66 Responses to Bromance: Sperm Heads Cluster to Get Ahead.


  1. “Bromance” – love it!

  2. Rajini Rao says:


    Hehe, having some fun at the expense of our male friends here 😉


  3. It has always puzzled me why sperm travel so slowly. If nature favours faster then why don’t they travel at 500MPH by now?

  4. Rajini Rao says:


    Donald Farmer , they are in a hostile enviroment 🙂


  5. Amazing what is being figured out about sperm competition. Btw: Humans (mostly!) fall in the 5% minority. is very controversial. It appears that modern humans’ sexual physiology is much more in keeping with multiple partner intercourse than “monogamy”. The biological anthropologists are telling us that the “standard model” of human pair bonding is falling apart like so much wishful thinking.


  6. Hostile to speed? Or is there something that disfavours speed?


  7. Donald Farmer they are very small. That alone limits how fast they can move.

  8. Yonas Kidane says:


    Ah, cooperation.  A trait that seems to diminish when they grow to be big and burly.


  9. Smaller is always faster isn’t it? In relative terms I mean.

  10. Rajini Rao says:


    Donald Farmer , I meant that the normal environment of the female reproductive tract is quite hostile to sperm: it is highly viscous, acidic and patrolled by immune cells that kill the invading sperm. At a cellular level, those may be pretty good speeds given the conditions. I can look around for comparisons of other migrating cells and report back.


  11. In addition, viscosity has an outsized importance for very small things. To a sperm, the fluid dynamics of traveling through a liquid are more like trying to propel itself through peanut butter than trying to swim through water.

  12. Rajini Rao says:


    So the fastest moving cells don’t have a patch on the sperm, clocking in at 5 micrometers a minute ..of course, they do not have flagella so the mechanism is different. See, http://www.popsci.com/science/article/2011-12/international-cell-race-clocks-cells-speeding-along-microscopic-race-tracks-science

  13. Chad Haney says:


    So I guessed right. Nice money shot. You are so good at aggregating information.


  14. Interesting, but those are applied across the board aren;t they? Can’t see how those disfavour speed. Evolution favoured speed enhancers ie the long tail and now we see clustering is also useful. Hmm, I guess it is that speed comes at a cost.


  15. Wow, bone marrow cells beat out breast cells. Who would of thought that !!!Fascinating Rajini. Thanks for sharing.

  16. Rajini Rao says:


    More comparisons: Bacteria, that do have flagella, move at 50 µm/sec, which is about 0.00015 kilometers/hr. That’s 10 body lengths per sec. A human can go around 5 body lengths per sec whereas a cheetah can do 25!


    When the sperm cluster, they must be able to generate a large propelling force that helps overcome the disadvantage of size mentioned above.


  17. Clustering must also favour survivability like herding does in the animal kingdom given the hostile environment you mentioned.

  18. Rajini Rao says:


    Wow, great link Joseph Moosman . Will check it out.

  19. Rajini Rao says:


    Excellent review, thanks Chad Haney . Longer sperm swim faster, so perhaps size does matter after all? 🙂

  20. jackie says:


    Wow, guys!!  Color me enlightened today, thank you.

  21. Sabin Iacob says:


    actually I remember reading that human sperm is quite complex in behaviour, with only a fraction of the fertile cells, the rest being divided between “killer” cells that seem to target sperm from other males and “blockers” who move slower and clog micro-channels in the mucus so sperm from other guys would have a hard time passing through


    The internet seems to provide contradictory texts on this, with the more academic looking ones (albeit older) saying there is no proof for killer sperm in humans.

  22. Rajini Rao says:


    Take a look at the review article that Chad Haney posted above, Sabin Iacob , it’s a nice read. I’ve not heard of killer sperm in humans..if you find a good reference, do share it here. Much of my work deals with movement of ions across membranes and the genes encoding these transporters have profound impact on sperm motility. The “funniest” mutant I’ve seen lacked a calcium pump that made the sperm lose all sense of direction. It could swim but had no idea where to go. The male mice were infertile as a result.

  23. Chad Haney says:


    I’ll add to my re-share when I get home. I have to add value, you know.

  24. Rajini Rao says:


    You have already added value by supplementing my vocabulary with the term ‘money shot”, Chad Haney 🙂

  25. Sabin Iacob says:


    I think the most credible “pro” piece is http://www.robin-baker.com/books/sperm-wars/status/#Killer1 by the author of the book where I’ve read this (he basically says subsequent experiments didn’t invalidate his conclusions)


    and the first one “against” that came up in my searches is


    http://eprints.whiterose.ac.uk/197/ (which may be the one Robin Baker is talking about)

  26. Rajini Rao says:


    Fascinating stuff, thanks..checking it out now, Sabin Iacob !


  27. hello, u quoted at a place -‘size matters’, It recalled me to ask that like human doe’s size differs in mouse,rabbit and other species..

  28. Rajini Rao says:


    Size of what, Avinash Dixit ?


  29. I know , this would be a question.., anyway i m asking the size of genital organ. suppose in animals ?

  30. Rajini Rao says:


    I’m sure they have differences in size, just as in humans Avinash Dixit . All rabbits are not the same size, so why should we expect the same for their ears, legs or any other part? 🙂


  31. This is a very interesting post Rajini Rao which (of course :)) I am now going to go investigate their social behavior. What is up???


  32. ok, still the question stands on its place.. Thnx


  33. Well done Rajini Rao , must share.

  34. Rajini Rao says:


    Thanks, Jose M. G. Guerreiro ! I thought the image looked like fireworks 🙂


    Cheryl Ann MacDonald , there are two species of deer mice that have completely different social behavior..one is monogamous and the other highly promiscuous. They seem to be used as models of social behavior and their genetic basis, from my readings for this post.


  35. Fireworks in our mind 🙂 Rajini Rao 

  36. Rajini Rao says:


    That’s a wonderful thought! I have such creative friends 🙂


  37. where from u collect the interesting facts.. I mean what is ur profession. That u have time to collect n share..+Rajini Rao

  38. Rajini Rao says:


    I am a scientist, Avinash Dixit . It’s not so hard for me to collect these interesting findings, and I like to share my love of science.


  39. In Vedic Astrology, The size could be known by a term as ‘Yoni’ And this is wonderful…

  40. Rajini Rao says:


    Oh yes, cells can display social and even altruistic behavior (i.e, for the greater good). Cool, is it not?

  41. Rajini Rao says:


    Haha, plausible theory Martin Geoffrey Lake 😉


  42. “Did you know that 95% of all mammals are promiscuous? Humans (mostly!) fall in the 5% minority. ”


    Perhaps the farming and industrial cultures have something to do with the sexual discipline in humans. It is not long ago that sexual correctness was imposed by organized religion. It still is the case in many places. Before the agricultural revolution, it may had been a different story.


    Sex At Dawn by Ryan and Jetha is quite enlightening about our sexual nature.

  43. Rajini Rao says:


    So monogamy is more advantageous to society as a whole, Akira Bergman ? Perhaps the added stability of the nuclear family unit helped focus man (I mean, humans!) on getting ahead.


  44. The emphasis is on the culture associated with the dominant economy, Rajini Rao . We are highly adaptable, and we seem to adapt our behaviour according to the demands of the economy, But we still are hunter-gatherers genetically and we miss some of the old ways.


    The fragmentation of the original tribal groupings was necessary for both farming and industrial cultures in increasing degrees. The problem now is that the states are abandoning their responsibility (or promise) of taking care of the nuclear family. A neo-feudal culture is on the rise economically, while a new global awareness is emerging, aided by the telecommunications revolution.


    I think reproductive culture will change this century, along with many other cultures.


  45. Rajini Rao Amazing post. I learnt so much today. One reason to keep checking G+. Thank You. 

  46. Rajini Rao says:


    The nuclear family is certainly fragmenting, Akira Bergman . I recall the statistics in the US are more children born out of marriage than ever before. Fascinating to follow, thanks for the insight. I’m fine with adaptation!


    Thanks, Ramesh Sundararajan , glad you enjoyed this 🙂


  47. The science of bromance


    Very interesting article about the nature’s intention to build alliance, if it’s necessary.


    Last year I had read an article about sperms, they swim in a swarm formation to survive the viscous enviroment.


    Because more of them survice the attacks of immune cells and can take more space on the ovum, that enemy sperms get not the chance to penetrate and put in their own cell material.

  48. Sunil Bajpai says:


    Fantastic lede: “In the race towards fertilization, speed matters. And you thought it was size?”


    Rajini Rao plus hundred!


  49. size doesn’t matter??? lol

  50. Kawthar A says:


    I enjoyed reading, while having my morning coffee at work! Fascinating read! 🙂

  51. Rajini Rao says:


    Awoke to shenanigans on Aida Hazlan post, Feisal Kamil 😉


    I crashed early last night..all this talk of swimming speeds exhausted me.

  52. Rajini Rao says:


    SciSun was busy but G+ has been glitchy of late. We were not trending even though we had half a dozen posts in What’s Hot and tons of # posts. As always, fun though.


  53. Rajini Rao glad you agreed, size does matter of course!!!


  54. wow, oh my god how is this possible, I can not think of anything more creative.


    In fact there are people with a great creativity, great as they seem firework. I know some people who’d never imagined how far your creativity, I am discovering day by day.


    Creativity and character go hand in hand, just see with all the depth and time, and there is, appears to the surface.


    It is fortunate to have friends who understand science, psychology, sociology, languages, art, and everything else, are true masters of knowledge that gives us the desire to bow before them mos, +José Guerreiro and +Rajini Rao. I bow to you for your friendship and mastery, in fact it is good to have friends like that with us, part of our life here as for example on google + and turn away those who do not want to be part of our friendships. Thank you because I have learned so much with sharing your knowledge that I apply to almost every day to have a better life, I bet it is you feel. So this firework in your minds. Well done 🙂 –

  55. Eric Hopper says:


    I do not believe humans fall into the minority. Many simply want to believe we do right now for cultural reasons.

  56. Arnav Kalra says:


    Cool pic.


    This post reminds me of an article. Rajini Rao you’d love reading http://goo.gl/0JQbP


  57. من میخام یه دوست داشته باشم که مفید باشه واز تنهایی رها بشم چکار باید بکنم


  58. میشه منو راهنمایی کنید


  59. انا ابي اعرف كيف يدركك وهوميت له. 1400سنه

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