Crustacea

A very large class of aquatic animals (phylum Arthropoda) with a chitinous exoskeleton and jointed appendages; e.g., the crab, lobster, crayfish, shrimp, isopods, ostracods, and amphipods. Some, such as certain copepods, are parasitic; others serve as intermediate hosts for parasitic worms which cause disease in humans and various other vertebrates. SEE ALSO: Copepoda. [L. crusta, a crust]

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crus·ta·cea .krəs-'tā-sh(ē-)ə n pl

1) cap a large class of mostly aquatic 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, shrimps, crabs, wood lice, water fleas, and barnacles

2) arthropods of the class Crustacea

crus·ta·cean -shən adj or n

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Crus·ta·cea (krəs-taґshe-ə) [L., from crusta shell] a large class of arthropods including the lobsters, crabs, shrimps, wood lice, water fleas, and barnacles.