The official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve
Elkhorn Slough Invertebrates: Fat Innkeeper Worm

Scientific Name:
Urechis caupo


Found at the Slough:
Mud flats

Did you know...
FIWs are eaten by otters, leopard sharks and rays here at the Slough.

The Fat Innkeeper Worms are common in the sandy mud of the Elkhorn Slough. They live in a U-shaped tunnel or burrow and have a unique method of eating. It secretes a slime net, which serves to trap small food particles. The worm circulates water through the tunnel, trapping food in the slime net. When the mucus net becomes loaded with food, it is loosened from its attachments and the entire net with its burden of food is swallowed by the worm.

Fat Innkeeper Worm mudAt least four other animals are known to live with the Fat Innkeeper Worm in its tunnel home. That's how it got its name. Frequent guests of the Worm include a fish called a goby, a small pea crab, a clam and a scale worm. They feed on food that the Innkeeper Worm leaves behind.

The Fat Innkeeper Worm is easy to spot from the surface. Look for hole with a small collar of mud poking up from the mud like a small volcano.

Fat Innkeeper Worms are eaten by bat rays, leopard sharks and otters, who suck or dig them out of their burrows.

You can see a larger than life model of a fat innkeeper worm at the Elkhorn Slough Reserve's visitor center.

VC worm


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This site is maintained by the Elkhorn Slough Foundation in partnership with the Elkhorn Slough National Estuarine Research Reserve