Mollusca aka the epitome of cool

1. Molluscaaka the epitome of cool Briana O’Leary Raissa Largman http://www.greenexpander.com/wp-content/uploads/2007/12/octopus.jpg

2. Animals Four major classes: 1. Polyplacophora: chitons 2. Gastropodia: snails 3. Bivalvia: clams, mussels, scallops, oysters 4. Cephalopoda: squids, octopuses, cuttlefish, chambered nautiluses Briana

3. Polypacophora http://reefguide.org/pix/thumb2/chiton4.jpg Chiton: marine, shell with 8 plates, foot used for locomotion, radula, no head. Raissa

4. Characteristics: Marine, freshwater or terrestrial Asymmetrical Body Usually has a coiled shell Shell reduced or absent in some Foot for locomotion Radula Gastropoda • http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/Content/green-snail-laman-400957-sw.jpg Briana

5. Bivalvia Marine and Freshwater Flattened shell with two valves Head reduced Paired gills No radula Most are suspension feeders Mantle forms siphons http://www.barrierreefaustralia.com/IMAGEGALLERY/giant-clam.jpg Raissa

6. Cephalopoda Marine Grasping tentacles Usually has suckers Can have shell/radula Locomotion through jet propulsion http://fractalontology.files.wordpress.com/2008/03/nautilus.jpg Briana

7. Basic Body Plan • Muscular foot • Visceral mass • mantle (fold of tissue over visceral mass) Body Cavity: Present. Fluid filled coelom. Raissa http://www.bio.miami.edu/dana/pix/ham.jpg

8. Body Symmetry: Varies. Gastropods: AsymmetricalOther classes are bilaterally symmetrical. http://open.live.bbc.co.uk/dynamic_images/naturelibrary_640_credits/downloads.bbc.co.uk/earth/naturelibrary/assets/o/oc/octopus/octopus_1.jpg http://www.bio.miami.edu/dana/pix/bodysymmetry.jpg Briana

9. Nervous System Nervous System: Present Nerve ring around the esophagus from which nerve cords extend Cephalopods: Highly complex system with brain. Estimated that an octopus has the same intelligence of a house cat. Raissa

10. Circulatory System Open system- heart pumps hemolymph through arteries into body spaces (constantly bathed) except in cephalopods- have closed circulatory systems http://www.cartage.org.lb/en/themes/sciences/lifescience/GeneralBiology/Physiology/CirculatorySystem/CirculatorySystem/TypesCirculatory/circsys_2.gif Briana

11. Digestive System Complete: mouth, anus complex stomach Many use radula to scrape up food, suspension feeders (many bivalves) collect food particles from water that passes over gills http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-21-ClamAnatomy-L.jpg Raissa

12. Excretory System Present: Nephridia: tubular structures that collect fluids and exchanges salts with body tissues. http://www.sharky1.com/Images/marine/mini%20cuttlefish.jpg Briana

13. http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Cephalopoda/Sub-squid.JPGhttp://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Cephalopoda/Sub-squid.JPG Locomotion/Musculature Varies Muscular foot (Chitons and Gastropods) Jet propulsion (Cephalopods) Lateral fins: (Cuttlefish) Bivalvia: Mainly sedentary http://www.pc.gc.ca/~/media/pn-np/bc/pacificrim/e-f/E-17_RAZOR_CLAM.ashx Raissa

14. Skeletal Type Soft bodied but most have a hard shell made of calcium carbonate. In some, the shell is absent or internalized. http://bama.ua.edu/~musselp/graphics/presentations/shell_show_2004_1.jpg Briana

15. Sensory Structures/Features Varies considerably between classes. Cephalopods have complex sensory capabilities. Giant Squids: Largest eyes in the animal kingdom Bivalves: Small eyes and sensory tentacles Gastropods: Eyes at the tips of tentacles http://www.nefsc.noaa.gov/press_release/2008/SciSpot/ss0810/T%20megalops%202038%20copy.jpg http://www.genomicon.com/wp-content/uploads/2009/04/snaileye.jpg http://www.augsburg.edu/home/biology/photoofmonth/scallopeyes-wide-big.jpg Raissa

16. Reproduction Mainly separate sexes with gonads: ovaries or testes. Many snails (gastropods) are hermaphrodites. Life cycle of many marine mollusks includes a ciliated larval stage: trochophore http://www.nicertutor.com/doc/class/bio1903/Locked/media/ch32/32_13Trochophore.jpg Briana

17. Gas Exchange Marine mollusks have gills. Water enters mantle cavity through a siphon, passes over gills, and then exits mantle cavity through another siphon. Terrestrial snails: lining of the mantle = lung http://kentsimmons.uwinnipeg.ca/16cm05/1116/33-21-ClamAnatomy-L.jpg Raissa

18. Other Unique Features There are twice as many species belonging to the phylum Mollusca than there are vertebrates. Gastropods: Torsion – Developing embryo’s visceral mass rotates up to 180 degrees causing its anus and mantle cavity to wind up above its head. http://www.palaeos.com/Invertebrates/Molluscs/Gastropoda/Images/torsion.gif Briana

19. QUIZ • Name the four classes that comprise Mollusca. • What type of excretory organ is present in Mollusca? A. Kidneys B. Nephridia C. No excretory organ D. Malpighian tubules

20. 3. What class has a closed circulatory system? A. Gastropods B. Bivalves C. Polyplacophora D. Cephalopods 4. Shells of Mollusks are • Absent • Internalized • Present • All of the above

21. http://www.fish.govt.nz/NR/rdonlyres/836B96BF-12FE-417D-AB49-4B46B2DB8729/0/ColossalSquid.jpghttp://www.fish.govt.nz/NR/rdonlyres/836B96BF-12FE-417D-AB49-4B46B2DB8729/0/ColossalSquid.jpg