Mollusca Soft bodied animals Mollusca General Info 150

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 Ca. CO 3

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=n. HVo. V 0 MVw. Sc nudibranch http: //www. youtube. com/watch? v=zs. Sc. H 4 TJ 7 NA chiton http: //www. youtube. com/watch? v=5 o. Exwxku. T_c octopus camoflauge, beak, and feeding http: //www. youtube. com/watch? v=9 az. BDt 0 kik&feature=Play. List&p=EF 6646 ECD 09 DBAB 3&index=0&playnext=1 flexible octopus body http: //www. youtube. com/watch? v=T 8 cf 7 t. Po. N 5 o&feature=Play. List&p=EF 6646 ECD 09 DBAB 3&index =1&playnext=2&playnext_from=PL octopus intelligence http: //www. youtube. com/watch? v=k_co. XZq 05 x. Y swimming clam http: //www. youtube. com/watch? v=UUNsrk. V_KIY&feature=related burrowing clam http: //www. youtube. com/watch? v=Xb. Owj. E 8 Ek. Sw&feature=Play. List&p=859 B 17 D 0 EA 1926 B 2&playnex t=1&index=2 chambered Nautilus