Crustaceans: Shrimps, Lobsters, Crabs, and Relatives

Crustaceans are the shellfish that have legs and sometimes claws: shrimps and prawns, lobsters and crayfish, and crabs. Like the molluscs, the crustaceans are an ancient and successful group of animals. There were primitive shrimps 200 million years ago; today there are some 38,000 crustacean species, the largest with a claw span of 12 feet/4 meters! The crustaceans are members of the large animal group known as arthropods, and are relatives of the insects. Like the insects, they have a body made up of several segments, a hard outer cuticle, or exoskeleton, that protects and supports the muscles and organs within, and many rigid appendages that are adapted to a variety of purposes, including swimming, crawling, and attacking prey. Most edible crustaceans are “decapods,” meaning they have five pairs of legs, one of which is sometimes greatly enlarged into claws. The meat of crustaceans is mainly skeletal muscle like that of fish and our land livestock. (Notable exceptions are the immobile barnacles, prized in Spain and South America.)