Arthropoda: Decapoda

Decopod crustaceans are classified as an order of crustaceans in the phylum Arthropoda, class Malacostraca. Because decapod crustaceans are grossly, this chapter uses the lobster as the model in most discussions, and describes important anatomic differences that occur in other decapods. The lobster\u27s body is elongated and divided into a cephalothorax and an abdomen. The hard carapace that makes up most of the cephalothorax is further divided into head and thoracic regions by various indentations on the carapace. Underlying the carapace epithelium is the “spongy” hypodermis composed of large vacuolated cells (the glycogen contents are removed during histologic processing). The gastrointestinal tract of decapods is divided into the esophagus, foregut, midgut, hindgut, anterior and posterior ceca, and digestive gland. The excretory system of a decapod crustacean is the primary means of eliminating nitrogenous wastes and is composed of several parts: a coelomosac, a labyrinth, a bladder and bladder duct, a nephridiopore, and the surrounding hemosinus