Figure 31.23 Crustacean Diversity (A) This decapod crustacean, a land crab, is found only on four islands in the South Atlantic Ocean. (B) This pillbug, a terrestrial isopod, can roll into a tight ball when threatened. (C) This tadpole shrimp, a branchiopod, is common in seasonal pools of the southwestern United States. (D) This minute copepod is found in freshwater lakes throughout Europe. (E) Gooseneck barnacles attach to a substrate by their muscular stalks and feed by protruding and retracting their feeding appendages.