The stalls of the Trouville Fish Market in the Calvados department give pride of place to crustaceans: crayfish, lobsters, crabs, shrimps, etc. Crustaceans - of which there are more than 50,000 species - are characterized by one common point: their exoskeleton. Their body is indeed covered with a hard envelope (the chitinous integumentary cuticle) secreted by the epidermis and rich in chitin. Chitin is impregnated with calcareous salts and contains pigments of various colors. This more or less rigid, thick, and flexible carapace is articulated at different points to allow the movements of the body. It goes through several sloughing to follow the growth of the crustacean.