Readers discuss swimming sperm, a fishing fox and more
Against the current
In the race to fertilize an egg, bull sperm that swim in groups travel on a more direct path than sperm traveling alone, James R. Riordon reported in “Sperm in groups outswim loners” (SN: 11/5/22, p. 14).
Given that sperm can’t see where they’re going, reader Donald Bruns wondered how the cells know the way to go.
Sperm make their way to an egg by swimming against a current of mucus that streams through the cervix and away from the uterus. That fluid flows in a thin layer on the surface of the female reproductive tract’s walls, Riordon says. The drag between the head of the sperm and the wall slows the sperm down and swings its tail downstream. This makes the sperm tend to swim into the oncoming current, he says.