Hermit crab

Size 5 cm, Most species have long, spirally curved abdomens, which are soft, unlike the hard, calcified abdomens seen in related crustaceans. The vulnerable abdomen is protected from predators by a salvaged empty seashell carried by the hermit crab, into which its whole body can retract.[3] Most frequently hermit crabs use the shells of sea snails (although the shells of bivalves and scaphopods and even hollow pieces of wood and stone are used by some species).[4] The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell.