Some mouse sperm can identify, and even cooperate with, its brethren
ScienceDaily (2010-01-25) -- Some mouse sperm can discriminate between its brethren and competing sperm from other males, clustering with its closest relatives to swim faster in the race to the egg. But this sort of cooperation appears to be present only in certain promiscuous species, where it affords an individual's sperm a competitive advantage over that of other males. ... > read full article
Back in the day I wrote a diddy on Sperm Warfare, which is a sweet book worth reading. It is also a controversial book, and the results have been challenged in the years since its publication. However, as one famous but egotistically arrogant professor told me, "don't believe any results until at least five different labs replicate the findings."
Which brings us to today's news item: more support for the idea that sperm are highly adaptable, multipurpose creations. For some time, it was believed that a large portion of sperm were not viable, thus not functional. Sociobiologically, something sounds wrong with this statement. Evolution doesn't waste such an important commodity.
Some truly wasted sperm are bound to be malformed, but not a significant number. Sperm Wars (and the research behind the book) suggests that there are many varieties of sperm, all of which are functional in their own way. Inseminators, warriors, blockers, and now cooperators. If sperm are shown to be doing something adaptive, then chances are this isn't going to be an isolated example.
The authors of the paper mention that most human sperm do not possess the necessary head shape to facilitate cooperative clustering. Human sperm is known for quite high variability, however, so I wouldn't rule out the possibility just yet. Again, at least five labs ought to reproduce the data. Plus, this could catch on in humans any day now.
Sperm competition is the counter to female cryptic choice, another devious reproductive tactics. Sperm Wars received considerable flak because the subject material is frankly disturbing, largely because it talks about the adaptability of infidelity. As with Wilson's original Sociobiology, it the book did not support any such actions. The fair view is to recognize the utility of all major strategies, paying due homage to the monogamous family which dominates human bonding.