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

2. 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

3. 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

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

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

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

7. 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.

8. 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

9. 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