Dept of Zoology, S.M.Joshi Collge , Hadapsar. Mollusca Tamboli Alija Z. Dept of Zoology, S.M.Joshi Collge , Hadapsar. S.Y.B.Sc

Structure Soft-bodied coelomates, multicellular, bilateral symmetry Divided into three parts: head-foot- muscular organ covered in cilia and rich in mucous cells visceral mass- it is the body cavity that holds the digestive, excretory, and reproductive organs; includes gonads, the kidney, the heart mantle- folds arise from dorsal body wall and enclose a cavity between themselves and visceral mass mantle cavity acts as lung

Structure Gills- specialized portions of mantle that consist of a system of filament as projections rich in blood vessels open circulatory system except cephalpods nephrida-tubular structures, remove nitrogenous waste outer surface of mantle secretes protective shell

Diversity Phylum: Mollusca Second most diverse phylum Over 110,000 species Phylum: Mollusca Classes Polyplacophora- marine mollusks oval bodies, not segmented Ex: chitons

Gastropods- primarily marine, freshwater and terrestrial mollusks, typically live in hard shell Ex: Snail and slugs

Cephalopods- active marine predators, well developed brains, intelligent invertebrates Ex: octopuses and squids blue ringed octopus

Nutrition Uniqueness Heterotroph Radula is used for feeding, it’s a rasping, tongue-like organ, chitinous teeth in rows Gastropods use radula to scrape algae and food materials Food is taken up by cells lining the digestive glands arising from the stomach, and then is passed into the blood. Uniqueness Mollusks have unique structure because some contain radula.

Reproduction Distinct male and female individual Few bivalves and gastropods are hermaphroditic Cross fertilization most common Aquatic mollusks-external fertilization Male and female release gametes in water and mix fertilization occurs Gastropods-internal fertilization- adaptation allows gastropods to live on land

Ecological significance Important source of food for humans Economic significance-pearls are produced in oysters Bivalve mollusks called shipworms burrow through wood submerged in the sea damaging boats, docks, and pilings. Zebra mussel invaded North American ecosystems it affected aquatic ecosystems. Snail fever-schistosomiasis