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Download 5/15/12 Mollusks - Solon City Schools
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Mollusk Characteristics • Unsegmented soft body • Mollusks have 3 main parts • Visceral mass: contains the internal organs • Modified Foot: – Muscular foot and/or tentacles • Mantle: fold that wraps around visceral mass & secretes the shell • Most have shell (internal or external) – Or remnants of a shell Mollusk Characteristics • Body Cavity- true coelom • Symmetry- bilateral • Organ systems-have organs for circulation, respiration, digestion, excretion, & nervous system • Respiration- most gills (some snails have simple lung) • Circulation- 3 chambered heart- most have open circulatory system (but squids & octopuses have closed circ. system) • Digestion- one way digestive system: separate mouth and anus • Reproduction- most are separate sexes and reproduce sexually by doing external fertilization (except snails which are hermaphrodites) • Nervous- ganglia, eyes, and nerves • Excretion- nephridia remove wastes Classes of Mollusks There are 7 classes of mollusks but this course will look at the 3 main classes • Class Cephalopoda – “head-foot” octopus and squid • Class Gastropoda – “stomach-foot” slugs and snails • Class Bivalvia – “two shells” clams, mussels, scallops . Class Cephalopoda •Types- octopus, squid, cuttlefish • Exclusively marine • Shell- “pen”- internal remnant of a shell • Use fins and siphon to move (jet propulsion) • Modified foot= tentacles • Fast swimming predators -use tentacles to catch prey • Use a beak-like jaw (radula) to eat prey • Have a special camera like eye Ex- Giant Squid OCTOPUS • Octopus in Aquarium SQUID NAUTILUS Cuttlefish • Cuttlefish Video Class Gastropoda • Types- snails, conches, limpets free-living; marine, terrestrial, fresh water • noticeable head • single shell, often spiral • muscular foot secretes mucus to form a slimy path to glide along • Feeding-most herbivores that scrape algae off rocks with radula- toothed tongue • Mantle- secretes shell SNAIL SLUG • Sea slugs- reproduction CONCH Snail Anatomy Class Bivalvia • Types- clams, scallops, oysters • marine and freshwater • gill used for gas exchange • all are sessile, filter feeders and filter food from the water • all have two part shells (bivalves) Muscular foot- used to dig into sand CLAM OYSTER MUSSEL SCALLOPS Squid External Anatomy Fins Mantle Siphon Squid Internal Anatomy Gills Fins Siphon Reproductive Organs
