Three Classes
1. Gastropoda (gastropods)~ slugs and snails 2. Bivalvia (bivalves) ~ clams and other two- shelled shellfish 3. Cephalopoda (cephalopods) ~ squids, octopuses and cuttlefish
1 Bodies of Mollusks
• A mollusk has a soft body which is usually covered by a hard outer shell. • Exceptions: – Slugs and octopuses have lost their shells through evolution – Squids have very reduced shells
Anatomy of a Mollusk
• All mollusks have: – Foot ~ the muscular foot helps it move – Visceral mass ~ contains the gills, gut, and other organs – Mantle ~ covers the visceral mass to protect the mollusks without shells • Most mollusks have: – Shell ~ protects the mollusk from predators and keeps land mollusks from drying out.
2 Symmetry of Mollusks
• Mollusks have bilateral symmetry. – The two halves of the body mirror each other.
Anatomy of a Snail (gastropod)
3 Anatomy of a Clam (bivalve)
Anatomy of a Squid (cephalopod)
4 Eating Behaviors
• Bivalves (clams) ~ filter tiny plant and bacteria from the water • Gastropods (snails) ~ eat with a radula (tiny tongue covered with teeth. – The radula is used to scrape algae off rocks and pieces of leaves and seaweed • Cephalopods (squid) ~use tentacles to grab their prey and put it in their powerful jaws.
Blue-ringed octopus
5 Market Squid
Moon Snail chasing its food
6 Achatina fulica Giant African Land Snail
The largest land snail known is the Giant African Land Snail. It can weigh up to 2 pounds and be 15 inches long.
Commonly Eaten Mollusks
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