Invertebrate Zoology

abdomen aboral ambulacral animal annelids antennae anteriorly anus arachnids arms arthropods asteroids attached barnacles blood body wall book lungs buccal burrow canal carapace cells chamber chelicerae chitinous ciliated coelom composed contains copepods coxae crabs crustaceans cuticle decapods digestive tract dorsal duct echinoderms eggs epidermis esophagus excretory exopodite extends eyes feeding female fibers Figure fresh-water fused ganglia ganglion genital gills gland gonads gonopore groove groups Hyman inner intestine larva lateral layer located longitudinal lophophore male mantle cavity marine maxillae maxillipeds median membrane modified mouth muscle nephridia nephridiopore nerve cord nervous system oral organs ossicles pair of legs parasitic pedipalps pharynx phylum plates pleopods podia polychaetes posterior posteriorly primitive proboscis radial region sand segments sensory sessile setae shell shrimp side species sperm spiders spines stalk statocyst stomach structure surface swimming telson tentacles terrestrial tissue trunk tube tubules uropods usually valves ventral worms