Why Thousands of 'Penis Fish' Washed Up on a California Beach

Nature works in mysterious ways. The latest example materialized at Drakes Beach near San Francisco, California, in early December, when visitors strolling along the shore stumbled upon what looked to be the discarded inventory of an adult novelty shop. In fact, it was thousands of Urechis caupo, a marine worm that bears more than a passing resemblance to a human penis.

The engorged pink invertebrate, which is typically 10 inches in length, is native to the Pacific coast and frequently goes by the less salacious name of “fat innkeeper worm.” Burrowing in sand, the worm produces mucus from its front end to ensnare plankton and other snacks, then pumps water to create a vacuum where the food is directed into their tunnel. Since it builds up a small nest of discarded food, other creatures like crabs will stop by to feed, hence the “innkeeper” label.

You can see the worm in "action" here:

Because the worms enjoy a reclusive life in their burrows, it’s unusual to see thousands stranded on the beach. It’s likely that a strong storm broke up the intertidal sand, decimating their homes and leaving them exposed. The event is likely to thrill otters, as they enjoy dining on the worm. So do humans: Penis fish are served both raw and cooked in Korea and China.