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Mollusks

Mollusks. Odyssey Expeditions. Jason Buchheim. Phylum Molluska. Means “soft body” Includes clams, snails, sea slugs, and octopus Freshwater, marine and terrestrial Most have external shell of calcium carbonate. Radula. General Characteristics. Posses a mantle

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Mollusks

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  1. Mollusks Odyssey Expeditions

  2. Jason Buchheim Phylum Molluska • Means “soft body” • Includes clams, snails, sea slugs, and octopus • Freshwater, marine and terrestrial • Most have external shell of calcium carbonate

  3. Radula General Characteristics • Posses a mantle • Circulates water through organism • Feeding, propulsion, and/or shell production • Gills or lungs found in mantle cavity • Posses a muscular foot • Used to crawl with • Tentacles in cephalopods • Posses a radula • Tongue bearing teeth used for feeding (like a conveyor belt)

  4. Classes • Class Monoplacophora • Class Polyplacophora • Class Aplacophora • Class Gastropoda • Class Bivalvia • Class Scaphopoda • Class Cephalopoda

  5. Class Monoplacophora • Relic class • Many fossilized mollusks belong to this class • Less than 20 extant (living) species • Single cap-like shell • Creeping foot • Found in deep water (2000 to 7000m)

  6. Class Polyplacophora • Chitons • Oval in shape • Eight over lapping plates • Creeping foot that adheres tightly to rocky surfaces • Mostly inhabit rocky intertidal zones • Feed on algae and other organisms on the rocks

  7. Ventral View Class Aplacophora • Worm-like • Small (<5mm) • No shell, have calcareous spicules in mantle • Inhabit deep water (200 to 7000m) • Creep or burrow • Very little known

  8. Class Gastropoda • Largest class of mollusks (30,000 species) • Snails and snail-like organisms • Well developed head with tentacles and eyes • Most possess single coiled asymmetrical shell • Most crawl with foot but some swim with it

  9. Gastropod Subclasses • Subclass Prosobranchia • Subclass Opisthobranchia • Subclass Pulmonata

  10. Subclass Prosobranchia • Mantle cavity anterior • Marine • Shelled • Many have operculum (hard disc attached to the foot that covers the opening to the shell for protection) • Some use mantle as camouflage • Includes conchs, whelks, cones, abalone, and drills • Herbivores and carnivores

  11. Subclass Opisthobranchia • Mostly marine • Shell reduced or lacking • Mantle cavity on right side, posterior, or even lacking • Some respire through skin or external gills • Mantle generally colorful and ornate • May have modified foot to swim with • Typically few inches in length • Includes sea hares, nudibranchs, sea slugs • Herbivores and carnivores (have very specific diets)

  12. Subclass Pulmonata • Typically terrestrial • Shelled (except slugs) • Mantle cavity modified into lungs • Includes terrestrial snails, freshwater snails and slugs • Typically herbivores

  13. Class Bivalvia • Consists of two hinged shells or valves • Gills used for filter feeding as well as respiration (water brought in and out by siphons while buried in sediment) • The mantle of some contains tentacles and eye spots to detect movement. • No head • Second largest molluscan class (8,000 extant species) • Freshwater and marine • Includes cockles, mussels, oysters, scallops, and clams

  14. Class Scaphopoda • Tusk or tooth shell (looks like elephant’s trunk) • Marine • Single elongated tube-like shell. • Burrowing • Modified foot for digging • Possess tentacles to capture interstitial (organisms found among sediment grains) • 2-6 cm long

  15. Jason Buchheim NOAA Class Cephalopoda • Elongated • Highly cephalized • Well developed nervous system • Foot modified into specialized arms and tentacles for prey capture • Shell external, internal, or absent • Includes nautilus, squid, octopus, and cuttlefish • Propulsion created by expulsion of water from mantle cavity

  16. Cephalopod Subclasses • Subclass Nautiloidea • Subclass Ammonidea • Subclass Coleoidea

  17. Subclass Nautiloidea • Nautilus • Only 4 extant species (most are extinct) • Multi-chambered external shell • Gas in chambers provides buoyancy (connected by central siphuncle canal and separated by septa) • Siphuncle used to add or remove gas to chambers • Many arms (~90) for prey capture

  18. Subclass Ammonidea • All members extinct • Coiled, external, multi-chambered shells • Complex septa with siphuncle found along outer axis of shell • Index fossils

  19. NOAA Jason Buchheim Subclass Coleoidea • Squid, octopus, cuttlefish • Internal or lacking shell • Eight arms with suckers • Squid and cuttlefish also have two tentacles for prey capture • Ability to camouflage is exceptional • Have large nerve cells used in research

  20. Resources • Barnes, Robert D. and Edward Ruppert. Invertebrate Zoology: Sixth Edition. Fort Worth: Saunders College Publishing, 1994 • Humann, Paul and Ned Deloach. Reef Creature Identification: Florida Caribbean Bahamas. Florida: New World Publications, Inc., 2003 • Kinsella, John, Drew Richardson and Bob Wohlers. Life on an Ocean Planet. California: Current Publishing Corp., 2006 • Taylor, Walter K. and Robert L. Wallace. Invertebrate Zoology: A Laboratory Manual Sixth Edition. New Jersey: Prentice Hall, 2002

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