By Harold McGee
All crustaceans share the same basic body plan, which can be divided roughly into two parts. The forward portion, or cephalothorax, often called the “head” in shrimp, is the equivalent of our head and trunk put together. It includes the mouth, sensing antennae and eyes, five pairs of manipulating and crawling appendages, and the main organs of the digestive, circulatory, respiratory, and reproductive systems. The rear portion, or abdomen, usually called the “tail,” is mostly a large, meaty block of swimming muscle that moves the fin-like plates at the back end. The major exception to this body plan is the crab, which seldom swims; its abdomen is a thin plate folded up underneath a greatly enlarged cephalothorax.