The Common Marine Hermit Crab (Pagurus bernhardus) is a saltwater aquatic decapod (10-armed) crustacean. It is also known as the Soldier Crab.
Hermit crabs include the Marine Hermit Crab, which lives in saltwater, and the Land Hermit Crab, which is terrestrial in tropical regions.
The Common Marine Hermit Crab is a crab inside a shell – its mobile home. It finds empty mollusc shells to live in. It has a long soft body – not like land crabs which have a hard exo-skeleton – which is why it looks for a hard shell to protect it. It can put its whole body inside the shell. As it grows, it looks for larger shells.
The Common Marine Hermit Crab has a spirally-curved soft body (abdomen) with a columella on the tip, which is used to hold onto the shell it occupies. It has 10 appendages (legs, called pereiopods), but two of them are claws, called nippers, pinchers, or chelipeds. Its large black compound eyes are at the end of an eyestalk. It has gills to breathe (like fish).