For years, scientists have thought sperm were propelled by their tails, which thrash back-and-forth with snake-like movements. But now technology has derailed that belief.
Using a state-of-the-art microscope, researchers have determined a sperm's tail lashes only to one side as the sperm spins around. "Sperm are very cheeky little creatures," says Polymaths Laboratory's Hermes Gadelha, the lead author of the study. "Our new research using 3D microscopy shows that we have all been victims of a sperm deception. If you want to see the real beating of the tail, you need to move with the sperm and rotate with the sperm."
Gadelha and his team have concluded sperm developed the rolling technique to prevent them from swimming in an endless circle. "Human sperm figured out if they roll as they swim, much like playful otters corkscrewing through water, their one-sided stroke would average itself out, and they would swim forwards," Gadelha says. "The rotation of the sperm is something that is very important."