PHYLUM MOLLUSCA

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

6. Other protostomes

7. 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

8. 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)

9. The Radula • “Toothed tongue” • Made of Chiton

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

11. 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

12. 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

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

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

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

16. 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

17. 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

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

22. Class Bivalvia “Clams, Mussels, Oysters” • Only class with out a radula • 2 shells (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

23. 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

25. Class Gastropoda “snails, limpets, and slugs” • Most diverse class in Phylum • Some have shells, some don’t • Most shells are 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

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

28. 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

29. 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

30. Vision • complex camera-like eyes • Camoflauge: they use their chromatophores to change brightness and pattern according to the background they see Ink • All have ink sac but nautilus made of melanin (pigment) • Confuses predator • Mixes with mucus to make a cloud

31. 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

32. 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

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