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Astacology
Crustaceans are invertebrate animals in the phylum Arthropoda, subphylum Crustacea, and include the barnacle, crab, crayfish, lobster, shrimp, water flea,
and pill bug. Although largely aquatic, a few crustaceans are found in terrestrial habitats. Of the nearly 40,000 aquatic species of crustaceans, only about
10% occur in freshwater habitats. Crustaceans have evolved a variety of specialized body forms and behaviors to cope with both aquatic and terrestrial
environments, however, all crustaceans share several characteristics: a hard exoskeleton; jointed, paired appendages; and three body regions (head,
thorax, and abdomen). The head and thorax regions are sometimes combined into a cephalothorax. [eng]
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