Crustacean

Crustacean, invertebrate animal (phylum Arthropoda) with a bilaterally symmetrical segmented body, including crabs, shrimps, lobsters, and barnacles. A few live on land and are parasitic, but most are aquatic, breathing by gills or through the skin, their heads covered with a protective shell and bearing paired series of antennae, 3 paired sets of biting mouth parts, and 2 lateral eyes (plus 1 medial). Periodically they shed their exoskeleton (external skeleton).