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PHYLUM MOLLUSCA

PHYLUM MOLLUSCA. are second only to arthropods in numbers of living animal species. Latin " Mollis" : Soft. 555 Million Years Ago. Coelomates-body cavity lined with mesodermal tissue. Other protostomes. Major Characteristics . Soft bodied animals with a calcium carbonate shell

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PHYLUM MOLLUSCA

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  1. PHYLUM MOLLUSCA are second only to arthropods in numbers of living animal species

  2. Latin " Mollis" : Soft

  3. 555 Million Years Ago

  4. Coelomates-body cavity lined with mesodermal tissue

  5. Other protostomes

  6. Major Characteristics • Soft bodied animals with a calcium carbonate shell • Some animals have internal shells or the shells have been lost through the process of evolution

  7. 3 zone body plan • 1. Visceral mass: encloses all organs • a gut with mouth and anus, a circulatory system, reproductive system, and an excretory system with kidneys • 2. Mantle: enfolds visceral mass and secretes shell and has chemical sensory organs • Mantle cavity encloses and protects gills • 3. Head/foot: holds sensory and motor parts • (nervous system)

  8. The Radula • “Toothed ribbon” • Used for feeding, scraping, drilling.

  9. The Foot • Anchoring • Locomotion • Burrowing • Swimming • Jet propulsion • Crawling • Gliding • Modifications • Different shapes and sizes

  10. The Siphon • Respiration: Brings in water to gills • Feeding: Transports food to digestive system • Reproduction: brings in sperm, releases eggs or sperm • Locomotion: jet propulsion

  11. The Shell • Usually hatch from egg with a tiny shell • Protection from predators • Prevents loss of body fluids on shore • New growth occurs at the shell lip in gastropods and along ventral margin in bivalves • Mostly composed of calcium carbonate • Some will have no shell or internal shells

  12. Classification • Kingdom Animalia • Phylum Mollusca • Class Polyplacophora • Class Gastropoda • Class Bivalvia • Class Scaphopoda • Class Cephalopoda

  13. Class Polyplacophora: “Chitons” • Has 8 shell plates: • Protection and flexing abilities • Can role into a ball • Surrounded by a structure called a girdle • Most live in intertidal zone • Strong foot for adhesion • Uses radula tipped with magnetite to eat algae

  14. Chiton reproduction • Separate sexes • Fertilization is external in the water column or in the females mantle cavity • Disperse in plankton as trochophore larvae • Free swimming • Rings of cilia • Settle on sea floor as juveniles

  15. Class Gastropoda (stomach-foot)“snails, limpets, and slugs” • Most diverse class in Phylum • Some have shells (univalves), some don’t • Most of the sea shells • Can be coiled, colored, and textured • Torsion process: visceral mass is turned 180-allows head to go into shell • 2-4 tentacles with eyes or sensory cells • Operculum-trap door to shell • Separate sexes: external fertilization • Trochophore larvae

  16. Feeding • Modified radula pertaining to food source • Herbivores, carnivores, detritovors, parasitism • Uses • Scrape • Drill • Dart • Secrete poison • Grasp

  17. Class Bivalvia “Clams, Mussels, Oysters” • Only class with out a radula • 2 shells (bi-valves) • Umbo-oldest part of shell • Strong abductor muscles keep it closed • Most are filter feeders • Foot is used to burrow • The scallops use jet propulsion to move • http://www.youtube.com/watch?v=e6Qsm9F1G7o&NR=1 http://www.youtube.com/watch?v=_2iXHBuSIJY&feature=related

  18. Bivalve Reproduction Separate sexes Hermaphroditic • Release sperm and eggs into water • Some species may brood taking sperm in through the siphon • Trochophore larvae • Males when young • When get bigger turn into females • Trochophore larvae

  19. Class Scaphopoda “Tusk Shells” • Most live in deep sea • Tubular shell with 2 open ends • Heads burrow in sediments • No gills: mantle acts as gills • Reproduction: • Separate sexes, some hermaphroditic • 1 egg is released at a time • External fertilization • Trochophore Larvae

  20. Feeding • Heads burrow in sediments • Have tentacles surrounding the foot called captacula that latch onto food • Radula breaks food into smaller pieces

  21. Class Cephalopoda “Octopus, Squid, Nautilus, and Cuttlefish” • Most intelligent of all invertebrates , complex nervous system • Muscular foot has been modified into a muscular hydrostat: moving items with no skeletal support but instead with muscles (our tongues are an example) • Found in all oceans at all depths • Chromotophores : colored pigments that allow them to change color or flash light

  22. Arms and tentacles • Only squid and cuttlefish have retractable tentacles for hunting • The arms may have suckers, hooks, or sticky palps • Males have a special arm to deliver a sperm packet to the female • Longest Mollusk: Colossal Squid :46 feet

  23. Vision • complex camera-like eyes • Camoflauge: they use their chromatophores to change brightness and pattern according to the background they see • http://www.ted.com/talks/david_gallo_shows_underwater_astonishments.html • http://www.youtube.com/watch?v=t-LTWFnGmeg&feature=related Ink • All have ink sac but nautilus made of melanin (pigment) • Confuses predator • Mixes with mucus to make a cloud

  24. Circulatory System • Closed system • 2 gill hearts • 1 systemic heart • Gills are very efficient because water is being forced fast through the mantle • Gills are smaller than in other mollusk, but because they are so efficient that is ok

  25. Reproduction • Separate sexes • Usually includes courtship with color changes • Most may die after spawning • Males transfer a sperm packet to the female by means of a penis or modified tentacle • The female then lays large egg clusters on the sea floor • No Trochophore stage like other mollusks-juveniles hatch out of eggs • http://www.ted.com/talks/david_gallo_shows_underwater_astonishments.html

  26. http://video.nationalgeographic.com/video/player/animals/index.htmlhttp://video.nationalgeographic.com/video/player/animals/index.html

  27. Circulation Open Closed • All but cephalopods • Pumps hemolymph throughout body • No veins • Drains to and from the gills • Slow moving animals • Cephalopods • Pumps hemocyanin through veins • 3 hearts • 2 gill hearts pump blood to gills • 1 systemic hearts pumps to rest of body • Fast moving animals

  28. The no squid zone? • the oxygen-minimum zone begins at about 500 meters depth and extends to about 1,000 meters

  29. Decrease in O2 • Animal respiration and decomposition of organic material • Warm liquids cannot hold as much gas as cold liquids

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