What is a Crustacean? Definition of CRUSTACEAN 1 :any of a large class (Crustacea) of mostly aquatic mandibulate arthropods that have a chitinous or calcareous and chitinous exoskeleton, a pair of often much modified appendages on each segment, and two pairs of antennae and that include the lobsters, shrimp, crabs, wood lice, water fleas, and barnacles. (reference: Merriam-Webster Online Dictionary)
Harlequin Land Crab
Crustaceans are invertebrate animals with shells such as crabs, shrimp, lobsters, crayfish, krill, barnacles, etc. that are part of the phylum arthropods which include insects and arachnids with segmented bodies, jointed appendages and an exoskeleton.
There are 67,000 species of crustaceans that range in size from Stygotantulus stocki at 0.004 in to the Japanese Spider Crab with a leg span of 12.5 feet and weighing as much as 44 pounds.
