Thousands of exposed 'penis fish' washed up on a beach in California

Joshua Bote | USA TODAY

After a powerful storm washed away their cover, thousands of unsightly — and phallic-looking — worms were left bare on a California beach.

Fat innkeeper worms — colloquially known as "penis fish" — washed up on Drakes Beach in Point Reyes, Calif., around fifty miles northwest of San Francisco, last Friday.

First reported by nature publication Bay Nature, the "penis fish" that washed ashore is the Urechis caupo, a type of spoonworm that primarily lives on the Pacific coast from southern Oregon to Baja California, according to naturalist Ivan Parr. At around 10 inches, its peculiar shape is perfect for coastal life, allowing it to dig a U-shaped burrow for itself and for other sea creatures, like crabs and fish, in sand or mudflat, he said.

The burrow that U. caupo makes is also useful for catching food, letting them take water in using a mucus "net" and sucking in plankton and other bacteria. It even leaves behind residuals for its guests, hence the "innkeeper" moniker.

But how, exactly, did thousands of these worms — again, not fish — end up washed ashore? Since their homes are constructed out of sand or mud, strong storms can wash them away. This renders them entirely visible during high-storm seasons such as the ones in El Niño years, per Parr.

Its predators include seals, seagulls and other fish and sharks.

Another spoonworm in the fat innkeeper family, the Urechis unicinctus, is commonly eaten in South Korea, Japan, China and Russia as a delicacy, often served raw.

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