Scientists Describe 'Incredible' Movements of Fruit Fly Sperm

Tiny fruit flies are packing some seriously big sperm—roughly 40 times larger than human sperm, each one nearly as long as the insect itself. How does that work? That's the question answered in a new study in Nature Physics focused on the male Drosophila melanogaster and its seminal vesicle, which stores thousands of 2-millimeter-long sperm despite being only a tenth of that length across, per a release. You might think that would result in a tangle of knotted tails, but that's not what researchers find, Popular Science reports.

They used fluorescent dyes and 3D electron microscopy to watch how the supersized sperm stay in line and found that the tightly packed cells generate slow, coordinated flows that can course through the entire storage organ for hours. While human sperm propel themselves by making waves through fluid, the fruit fly sperm push off other sperm moving in the opposite direction. Those contact-driven movements keep the long tails stretched and less likely to tangle, the team says. As study co-author Brato Chakrabarti notes, per the Simons Foundation, "It's an incredible system from [an] evolutionary perspective and from a mechanics perspective."