Mollusc Characteristics• Unsegmented soft body

– Visceral mass• Molluscs have a Modified Foot

– Muscular foot and/or tentacles• Have a mantle (fold in the body wall

that lines the shell) • Most have shell (internal or external)

– Or remnants of a shell• Pen in squid

Tentacles/ modified foot head Mantle

cavityShellfootMantle

Classes of MolluscsThere are 8 classes of molluscs but this course will look at the 3 main classes.

• Class Cephalopoda –

octopus and squid

• Class Gastropoda –

slugs and snails

• Class Bivalvia – clams,

mussels, scallops

Class Gastropoda

• free-living; marine, terrestrial, fresh water• noticeable head• single shell, often spiral• muscular foot is attached near the stomach area

Class Bivalvia

• marine and freshwater

• gill used for gas exchange

• all are sessile, suspension feeders and filter food from the water

• all have two part shells

(bivalves)

A giant clam can be 4 to 6 feet in diameter!

Other Bivalves

• Limatula strangei. Some bivalves, such as the scallops are able to actively move when endangered by vigorously flapping their shells and squirting out jets of water. Limatula also moves very vigorously when disturbed. The tentacles around the mantle edge are sticky, very mobile and parts can break off them when the animal is disturbed, leaving a potential predator with a sticky writhing worm-like object to deal with as the Limatula escapes (25mm).

The bivalves are the second largest class of molluscs. They differ from snails in having two shells, usually mirror images of each other. Some like oysters and mussels live attached to rocks and other hard surfaces while others, like pipis, burrow in sand. Leptonoidean bivalves (in picture) are a group which usually live commensally with other animals. Most have a large foot and are active crawlers (1mm).

Scallop with a “buddy” on top!

Bay Scallop before cooking

Inside of Bay Scallop

Cooked scallops! YUMMY!

Class Cephalopoda• Exclusively marine• Shell- “pen”- internal

remnant of a shell• Use fins and siphon to

move• Modified foot= tentacles• Fast swimming

predators-use tentacles to catch prey

• Have a special camera like eye

Ex- Giant Squid

Squid External Anatomy

Siphon

Fins

Mantle

Squid Internal Anatomy

Squid swimming with Mrs. Ross while scuba diving off the coast of Jamaica

Can you see the squid?

Do you think these squid are related?

BEFORE….

AFTER!

So, when do I get to see you and your relatives photos?