Everybody knows the shortest distance between two points is a straight line, and now Harvard researchers have evidence that sperm have been taking the familiar axiom to heart.
Though competition among individual sperm is usually thought to be intense, with each racing for the chance to fertilize the egg, Harvard scientists say in some species, sperm form cooperative groups that allow them to take a straighter path to potential fertilization.
A new study, conducted by Heidi Fisher, a post-doctoral student working in the lab of Hopi Hoekstra, Howard Hughes Investigator and Professor of Organismic and Evolutionary Biology and Molecular and Cellular Biology and the Alexander Agassiz Professor of Zoology in the Museum of Comparative Zoology and post-doctoral student Luca Giomi working with L Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics shows that in Peromyscus maniculatus, a species of deer mouse known to be promiscuous sperm clump together to swim in a more linear fashion. The study is described in a July 23 paper in Proceedings of the Royal Society B.
"We generally think that each individual sperm cell swims its little heart out to get to the egg," Hoekstra said. "But it had been discovered that, in at least a handful of organisms, sperm will cooperate and swim as a group."
Exactly why sperm clump together, however, had remained a mystery until now.
"We had some hints that cooperation was enhancing their swimming performance, but what we didn't understand was how it was helping," Fisher said. "With this study, we combined a mathematical model with much finer-scale measurements that looked at groups that ranged from single sperm cells to groups of as many as 30 cells. What we realized was that that while their overall speed wasn't increasing at all, but that the time it took them to go from point A to point B was d
|Contact: Peter Reuell|