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Mollusk Characteristics

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)

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Mollusk Characteristics

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  1. 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

  2. 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)

  3. Mollusk Characteristics • 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

  4. 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

  5. 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

  6. OCTOPUS • Octopus in Aquarium

  7. SQUID

  8. NAUTILUS

  9. Cuttlefish • Cuttlefish Video

  10. 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

  11. SNAIL

  12. SLUG • Sea slugs- reproduction

  13. CONCH

  14. Snail Anatomy

  15. 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

  16. CLAM

  17. OYSTER

  18. MUSSEL

  19. SCALLOPS

  20. Squid External Anatomy Fins Mantle Siphon

  21. Squid Internal Anatomy

  22. Gills Fins Siphon Reproductive Organs

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