• Crustaceans, members of the subphylum Crustacea, have two pairs of antennae. Most crustaceans have a pair of chewing mouthparts called mandibles and one pair of branched appendages on each body segment. The exo-skeletons of many crustaceans contain large amounts of calcium carbonate.
• Crustaceans include shrimps, lobsters, crabs, crayfish, barnacles, isopods, copepods, and water fleas. Most crustaceans are aquatic, use gills to respire, and have a larval stage called a nauplius.
• The body of a crayfish is divided into a cephalothorax and an abdomen. The appendages on each body segment are specialized for sensing, feeding, respiration, locomotion, or reproduction.
• Crayfish have a digestive gland that is near the stomach and that secretes enzymes for digestion. Walking circulates water across the gills for respiration. The circulatory system is open. Green glands assist in excretion of excess water that enters the body by osmosis.
Vocabulary nauplius (p. 726) cirrus (p. 727) isopod (p. 727) decapod (p. 728)
cephalothorax (p. 728) thorax (p. 728) carapace (p. 728) abdomen (p. 728)
antenna (p. 728) antennule (p. 728) cheliped (p. 728) swimmeret (p. 729)
telson (p. 729) uropod (p. 729) digestive gland (p. 729) green gland (p. 730)
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