Rough Keyhole Limpet

Rough keyhole limpet, Diodora aspera, is a species of sea snail in the family Fissurellidae, the keyhole limpets, found along the Pacific coast of North America. Though superficially similar to the common limpet, it is only distantly related and is easily distinguished by a small hole near the apex of its conical shell, used to expel waste and respiratory water. It often hosts a small scaled polychaete worm as a commensal living inside its shell, and when attacked by a starfish it extends flaps of its mantle over the shell to help drive the predator away.