38-2 Arthropoda  Phylum: Arthopoda  Subphylum: crustacea  lobster, crayfish, shrimp, sow bugs, pill bugs, daphnia and barnacles

Daphnia

Barnacles

I. Digestion  Food  esophagus  stomach  intestines and digestive gland  anus  Stomach: contains teeth made of chitin and calcium carbonate which grind food into a fine paste  Intestines: final digestion and absorption  Digestive gland: secretes enzymes to aid in digestion

II. Respiration Gills  Located at base of each walking leg and extends up into a chamber under the carapace  As crayfish walks, this helps circulate water across gills

III. Circulation Open circulatory system  Dorsal heart pumps hemolymph into regions of the body and then into hemocoels where tissues are nourished. The hemolymph then passes through gills where it exchanges carbon dioxide for oxygen and then returns to heart.

IV. Excretion Green Glands  Eliminates excess water through a pore at the base of the antennae

V. Neural control: Nervous system  Brain consists of pair of ganglia above esophagus  Receives impulses from eyes, antennules and antennae  Ventral nerve cord carries impulses down body  Sensory hairs on body also pick up impulses  Eyes are compound (contains many lenses) and set on movable stalks  At base of each antennule is an organ which is used for orientation