All Things Considered has this story today:
On the Delaware Bay shore, there's a swinging party that's been taking place for millions of years.Those female crabs have this one night a year to, well, be mounted by up to 13 males:
If you're a female horseshoe crab, then it's your night. You'll swim to shore, meet a special someone and he'll clasp onto the back of your shell. You and he will crawl onto the beach together, where you'll spawn at high tide under the light of the full moon.
But the mate attached to your shell is not your only tryst. On this night, you will mate with up to 13 males, all at the same time. Thousands of horseshoe crabs will pile on top of one another, glistening shells covering the beach for miles.
Wow. The mind boggles.