How difficult it must be to have to face off as a sperm! From the moment you arrive you are racing along in a wave of competitors. Now complicate that with the fact that your host mammal has been making the rounds! Live together die alone (if you know what that means its our secret) is apparently the biological answer.

According to the work published in the January 20th edition of the journal Nature by biologists Heidi S. Fisher and Hopi E. Hoekstra some mice sperm are able to differentiate between those related to them and competitors. The clustering of sperm only occurred in the promiscuous species.

“The race among sperm toward the egg is fierce, but never more so than when sperm of different males compete,” said Fisher, a postdoctoral researcher in OEB. “In some species where females mate with multiple males, groups of sperm join forces to outswim their uncooperative competitors. We’ve shown that, in deer mice, cooperation only occurs among close relatives — sperm from the same male.”

This ability of sperm to discriminate between related and unrelated sperm is not seen in monogamous species, in which sperm of different males are unlikely ever to interact. The results suggest that competition among males drives cooperative behavior among their sperm.

Fisher and Hoekstra studied sperm from two species of deer mice, Peromyscus polionotus and Peromyscus maniculatus. Although closely related, the species differ greatly in their sexual behavior: P. polionotus is monogamous, while P. maniculatus females are promiscuous, mating with successive males as little as one minute apart.

Moore also investigated whether human sperm clusters in the same way, finding little evidence that it does.

“Most rodent sperm have hooked heads, enabling mouse sperm to cluster together,” Fisher said. “In humans, the sperm head is rounder, which does not facilitate clustering.”

The work is described this week (released Jan. 20) in the journal Nature by biologists Heidi S. Fisher and Hopi E. Hoekstra of Harvard University.
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08736.html
http://www.oeb.harvard.edu/

Source Article from Harvard Science