The Crustacea The Crustacea are a mainly marinegroup including crabs, lobsters,crayfish, and woodlice. Woodlice areterrestrial but need to live in cooldamp places to avoid drying out.Crustacean body structure Crustaceans have highly segmentedbodies, although in some of the moreadvanced species the segments havefused together into larger blocks. Theoverall body plan follows standardarthropod structure with head, thorax,and abdomen, although the head andthorax are fused into a region calledthe cephalothorax. The head is well supplied with senseorgans, including two pairs ofantennae. In many crayfish and lobsterspecies, a pair of front legs has beenhighly modified into pincers(chelipeds). The marine crustaceans like lobstersand crayfish grow in size by moltingtheir exoskeleton, growing rapidly, andthen reforming a tough exoskeleton.This can occur a number of timesduring an animals life. The moltingand redevelopment of the exoskeletonimposes a significant cost on theanimal in terms of calcium, and this isrecovered from the old exoskeletonbefore it is shed. Crustaceans can lay eggs containingeither larvae (small shrimps, lobsters,and crabs) or fully formed, but small,adult forms (crayfish).Kingdom Animalia:CrustaceaabdomenexoskeletonsegmentthoraxKey words Diagram Visual Information Ltd.cephalothoraxabdomenCrayfishLateral viewVentral viewDorsal viewwalking legs pleopodsantennachelasecondantennafirstantennalabrumpalp of mandiblemandiblethirdmaxillipedfirst pereiopod(walking legs)fourthpereiopodpleopodssternite (ventral exoskeleton)uropod protopoditeuropod exopoditeuropod endopoditetergite (dorsal exoskeleton)telsoncarapacecephalicgroovecompound eyecheliped