Mollusca Soft bodied animals

Mollusca General Info 150,000 known species Most mollusks are marine, but some live in fresh water environments Mollusks are soft-bodied animals that are sometimes protected by a hard shell

Symmetry in Mollusca In the beginning of the life cycle of a mollusk, bilateral symmetry is present, but this may be lost by adulthood as they have spiral development

Body Development in Mollusks 3 main parts: muscular foot, a visceral mass, and a mantle The muscular foot is used for movement The visceral mass contains most of the internal organs The mantle is a fold of tissue that secretes the shell if present, covers the visceral mass The shell secreted by the mantle is made of CaCO3

Movement In Polyplacophora, Gastropoda, and Bivalvia, a muscular foot is used for locomotion In Cephalopods, siphon made from the mantle allows jet propulsion

Germ Layers and Coelom Open circulatory system, where the body cavity is a blood-filled hemocoel filled with hemophyll (blood and lymph between organs)

Life Cycle/Reproduction Starts with a ciliated larva, otherwise known as a trochophore No true segmentation unlike Annelids Normal sexual reproduction is present, although some are hermaphrodites Most have external fertilization

Specialized Tissue The radula is a tongue-like structure that scrapes up food and is modified into a beak in the octopus The mantle cavity is a water-filled chamber that houses the gills, anus, and excretory pores Torsion is a process in Gastropoda where one set of muscles grows faster than the other, which creates the shell to grow in a spiral pattern

Chiton (Polyplacophora) Octopus (Cephalopoda) Snail (Gastropoda) Squid (Cephalopoda) Scallops (Bivalvia)

Mollusk behavior http://www.youtube.com/watch?v=nHVoV0MVwSc nudibranch http://www.youtube.com/watch?v=zsScH4TJ7NA chiton http://www.youtube.com/watch?v=5oExwxkuT_c octopus camoflauge, beak, and feeding http://www.youtube.com/watch?v=9-azBDt0kik&feature=PlayList&p=EF6646ECD09DBAB3&index=0&playnext=1 flexible octopus body http://www.youtube.com/watch?v=T8cf7tPoN5o&feature=PlayList&p=EF6646ECD09DBAB3&index=1&playnext=2&playnext_from=PL octopus intelligence http://www.youtube.com/watch?v=k_coXZq05xY swimming clam http://www.youtube.com/watch?v=UUNsrkV_KIY&feature=related burrowing clam http://www.youtube.com/watch?v=XbOwjE8EkSw&feature=PlayList&p=859B17D0EA1926B2&playnext=1&index=2 chambered Nautilus