50,000 or more species of molluscs. They share 3 major sets of characteristics:

Body enclosed by a blanket-like mantle that secretes a shell made of calcium or some other stiff structure.

A mantle cavity between the mantle and the internal organs; the anus, reproductive, and excretory ducts open into the mantle cavity.

A ventral, muscular foot that is highly modified among the various groups of molluscs.

Three main parts of a Mollusca1. Visceral mass – Location of Organs 2. Mantle tissue makes a calcium

carbonate shell (may be reduced)3. Foot = muscular structure modified in

some way (how determines class)- used for movement

Reduced coelom

Free-living, multicellular animals Invertebrates (lack a backbone) Unsegmented Have a true coelom – BODY ADVANCE Bilateral symmetry Have a true heart Simple to complex nervous system Open circulatory System – BODY ADVANCE

Some mollusc habitats include: Marine (mostly) Freshwater (a few) Land (a few)

Mollusc niches (life-style): Most live on the ocean bottom and are mostly

sedentary Some are free-swimming (the cephalopods)

There are seven mollusc classes in total six major ones, of which we will study 3 of them.

Those 3 classes are: Gastropoda (gastro=body cavity; poda=foot)

Ex. Common garden snail, abalone, turban snail Bivalvia (bi=two; valvia=valves)

Ex. Clam Cephalopoda (cephalo=dealing with head; poda=foot)

Ex. Squid, octopus, etc.

Gastropods- The most common type of molluscs….Snails

Bivalves- The body is compressed into a two valved shell….Scallop

Cephalopods – Most agile of the molluscs complex nervous system and a reduction or absence of a shell. Highly Cephalized

Most popular class of molluscs. Consists of snails and snail-like

creatures. Specific characteristics:

They have a dorsally located shell (often coiled).

They have a well-developed radula. Visceral mass (organs) is located

inside the shell. Their visceral mass is rotated 180 degrees during development.

They are herbivores or predatory (carnivorous).

Habitats include: ocean, lake, river bottoms, coastal shores, and land.

1.Class: Gastropoda (gastro=stomach; pod=foot) or Univalvia (one shell)

ex: snail, abalone, conch

Their bodies are covered by one shell, except for the nudibranch.

Special tongue (radula) with a ribbon of flexible teeth on its surface works like a mini-chain saw. It is used to scrape surfaces for algae or to cut into other shells.

Precious Wentletrap

Most are benthic herbivores, although the dog whelk is carnivorous.

A. OpenB. ClosedC. They do not have

a circulatory system.

Open

Closed

They

do not hav

e a circu

lator..

.

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A. 2B. 4C. 3D. 6

2 4 3 6

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A. GastropodB. PseudopodC. CephalopodD. BiValve

Gastro

pod

Pseudopod

Cephalopod

BiValv

e

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A. PodiaB. RadulaC. MantleD. Visceral mass

Podia

Radula

Mantle

Viscer

al mass

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A. NudibranchB. Cuttle fishC. OctopusD. Conch

Nudibranch

Cuttle fish

Octopus

Conch

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Seconds Participant Seconds Participant

Specific Characteristics: They have no head. They have two shells held

together by powerful muscles. They have a ventrally located

foot that sticks out between the two valves.

Habitats include: marine and freshwater.

They tend to burrow into soft mud or sand or attach to rocks or other shells.

Large gills are used for respiration and filter feeding.

Food is trapped by mucus on the gills and moved by cilia. Water enters and exits through siphons.

2. Class: Pelecypoda or Bivalvia (two footed, also two shells) ex: clams, oysters, scallops

They are benthic, planktivores who filter sea water through an incurrent and excurrent pore. Some are sessile (oyster) others swim by opening and closing both shells (scallop).

Byssal ThreadsOn Mussels

Class BivalviaClams, Oysters, Mussels

Oysters

Scallops

Contains the largest molluscs. HIGHLY CEPHALIZED Specific Characteristics:

May lack a shell (like an octopus) Shell may be reduced to a stiffening rod (like

the squid or nautilus) A Chitionous Pen The foot is highly modified to form a group of

tentacles around the mouth. They are found in deep and shallow waters

along many coasts. Squids & Nautilus are free-swimming and move

very quickly. Octopuses are found among rocks or crawling on the bottom of the ocean.

Complex brain, two lateral eyes, excellent eyesight.

We will dissect a squid. If you are allergic to shellfish then speak up now!!!

Class Cephalopoda

- mouth has a sharp beak for eating worms, fish, etc.

- moves by jet-propulsion, mantle fills with water which can be squirted out to propel them backwards

- chromatophores in the skin change colors when the animal is alarmed and for camouflage

- ink gland is used as a “smoke screen” for a quick escape

- eyes have a cornea, lens and retina; excellent vision

In the octopus, reproduction is by internal fertilization. During the 30 days until hatching, the female carefully aerate, cleans and watches the eggs - never leaving even to eat.

The female usually dies from exhaustion and starvation soon after they hatch.

Cuttlefish Chambered Nautilus

The cuttlefish has an internal shell that is sold to pet stores as a source of calcium for birds. – a cuttle bone

Cuttlefish

The cuttlefish are masters of Color change

Cells in their skin called chromatophores cells which are controlled by muscles to create different colors.

A. HeadB. FootC. ArmD. False

Head

Foot

Arm

False

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A. CuttlefishB. OctopusC. SquidD. Sponges

Cuttlefish

Octopus

Squid

Sponge

s

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Seconds Participant Seconds Participant

The spiraled shell of the chambered nautilus is lined with mother-of-pearl and is perfectly proportioned mathematically.

Gas and liquid exchange occurs through the walls and allows the nautilus to regulate buoyancy.

If an irritant such as a grain of sand gets trapped under the oyster’s mantle, it secretes a coating of a pearl-like material called nacre. Selected oysters are carefully raised to produce pearls of various sizes and colors.

Oysters are at the center of the aquaculture industry and are raised for culturing pearls.

Bioluminescence