Oyster Crab

An oyster crab is a very small crab that lives inside the shell of a living oyster. It is a commensal organism, using the oyster as shelter while usually causing little direct harm.

The oyster shell provides protection from predators and a stable place to live. The crab can feed on food particles and material brought into the oyster as the oyster filters water.

Oyster crabs occur along the North American Atlantic coast in association with living oysters. Their distribution follows suitable oyster beds and coastal shellfish habitat.

It is generally described as commensal rather than a true parasite. The crab benefits from shelter and food opportunities, while the oyster is not normally consumed as the crab's host tissue.