mollusk

a member of phylum Mollusca

mollusk structure

have 3 germ layers; exhibit cephalization and bilateral symmetry; all have digestive, circulatory, nervous, and respiratory systems some have a nervous system composed of ganglia; aquatic use gills to breathe; aquatic also circulate water through two siphons

radula

platelike structure near the mouth of many mollusks; bears many tiny teeth used for scraping up food into the animal's mouth

siphon

one of a pair of tubes in many aquatic mollusks used to draw in or expel water

gastropods (e.g. slugs and snails)

rhinophores (sensory organ; think lunar moth eye-brows); external gills; singular foot; visceral mass; mantle

visceral mass

the portion of a mollusk's body that contains its internal organs

mantle

the sheath of tissue that covers the body of a mollusk

cephalopods (e.g. cuttlefish and octopi)

have feet that are divided into sucker bearing arms for catching prey; chromatophores (pigment-containing cells); eyes; visceral mass; mantle

bivalves (e.g. scallops, oysters, mussels, and clams)

mantle; shell; visceral mass; mouth; foot; eyes

mollusk reproduction

usually sexually; simpler mollusks reproduce via external fertilization, while more complex mollusks reproduce via internal fertilization

mollusks in the environment

have roles in a variety of ecosystems (e.g. eat algae, detritus, and even each other! Find refuge and food in coral reefs); food source for humans; medical resources (e.g. cuttlefish ink)