The Animal Kingdom Web Links Science Main Index Crustaceans have a hard, external shell which protects their body. Crustaceans have a head and abdomen. The head has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system. The abdomen also has appendages, such as legs, for crawling and swimming.
Many crustaceans also have claws that help with crawling and eating.