Arthropods Hermit crab in a whelk shell. Arthropods Crabs, lobsters, shrimp, barnacles and many other animals belong to the phylum arthropods.
All arthropods have a hard exoskeleton made of chiton, a type of protein.
This shell provides protection for the animals, and gives support for the attachment of the arthropod's muscles. Although arthropods grow, their exoskeletons do not grow with them. Lost limbs can gradually be regenerated after successive moltings. The most common type of amphipods are the gammarids. You probably know them better as beach hoppers, side-swimmers, scuds, or sand fleas.