Your Sperm Velocity Has Been Measured and Found Wanting

Human sperm can swim pretty fast, most of the time, but they've got nothing on the sperm of deer mice. What is the deer mouse's secret? Recently, a Harvard professor created a mathematical model of sperm behaviors to figure it out.

Deer mouse sperm image via Heidi Fisher

Over at Not Exactly Rocket Science, Ed Yong explains that the answer is teamwork:

Take the deer mouse. The sperm of this common North American rodent have heads that are flattened paddles with small hooks, rather than the usual round teardrops. These heads can stick to each other, forming clusters of up to 35 sperm. Scientists have reasonably assumed that the sperm swim better as a team, but that's not always the case. Sometimes, the groups are faster; sometimes, they barely move.

Heidi Fisher from Harvard University knows why. Together with Luca Giomi and L Mahadevan, she created a mathematical model that simulated the swimming sperm. It showed that while groups don't swim any faster, they do swim straighter because each cell cancels out the wobbling movements of its neighbours. Their speed stays the same but their velocity—their speed in a straight line—goes up. "The aggregate gets to the finish faster," says Fisher.

Team players win the egg. Of course, that's only if the team is the precise right size. Read the rest of the article to find out why.