Worms Are Picky Ejaculators

Earthworms don't appear to be the most astute observers—they have no eyes, they wander foolishly onto heavily trafficked sidewalks whenever it rains, and they have simple pairs of cell clusters for brains. But when it comes to sex, these hermaphroditic critters can detect something that many humans can't: whether or not their partner is a virgin. And they compensate the sperm load accordingly. Earthworm sex is fascinatingly complex and slimy. It begins when two worms rub against each other, causing the clitellum (that swollen thing that looks like an armband) to ooze a tremendous amount of mucus and enclosing themselves in a slimy tube of lovemaking. In a process that can last up to an hour, the worms then ejaculate sperm into the slime, which makes it way into the other worm's sperm repositories. The earthworms then separate and slither their separate ways. Meanwhile, eggs are produced in a separate ...