Section 2

objectives

• Describe the characteristics of crustaceans.

• Compare aquatic crustaceans with terrestrial crustaceans.

• Explain the functions of the appendages on a crayfish.

• Summarize digestion, respiration, circulation, excretion, and neural control in crayfish.

vocabulary nauplius cirrus isopod decapod cephalothorax thorax carapace abdomen antenna antennule cheliped swimmeret telson uropod digestive gland green gland

Subphylum Crustacea

Th e subphylum Crustacea contains about38,000 known species. Crustaceans are abundant in oceans, lakes, and rivers, and a few species live on land. Some crustaceans are sessile, while others move by walking on legs, swimming with paddle-like appendages, or drifting with the currents.

figure 36-4

The free-swimming nauplius is an early stage in the development of most crustaceans. It has one eye and three pairs of appendages.

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