A large class of aquatic animals (phylum Arthropoda) with a chitinous exoskeleton and jointed appendages; the crab, lobster, crayfish, shrimp, isopods, ostracods, and amphipods. Some, (certain copepods), are parasitic; others serve as intermediate hosts for parasitic worms that cause disease in humans and various other vertebrates.
[L. crusta, a crust]
See Also: Copepoda
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Examples: glitazone, GI cocktail, etc.