4. molluscs clams and octopus

Phylum Mollusca

Almost all have the following in common:

ShellMantleFootRadula

Phylum MolluscaClams, Cockles, Mussels - Class Bivalvia

• All possess a hinged two-valved shell.

• Shells are composed of Calcium carbonate.

• Body flattened laterally.

• Lack of cephalization• Do not have a radula

Phylum MolluscaShell, Mantle, Foot, Radula

Phylum MolluscaClams, Cockles, Mussels - Class Bivalvia

Phylum Mollusca Clams, Cockles, Mussels - Class Bivalvia


• Blue Mussel- Mytilus sp.

• Suspension feeders• Very large gills that

collect food particles• Great to eat, but

also great sentinels for the environment


• Giant Pacific Oyster Crassostrea sp.• Sedentary• Blue mussels attach

by byssal threads

the oysters cement to

rocks

• Oysters are ambisexual. Start out as males for three years then become female.


• Mahogany Clam Nuttallia sp.

• Most common clam on our beach

• Introduced to our beaches 20 years ago, range is from Puget sound to Alaska?


• Soft shell Clam Mya sp.

• Shells suited to their name.

• Located near fresh water streams

• Develop leukemia if habitat is contaminated with PCBs


• Geoducks Panopea sp • The world’s largest

burrowing clam (up to seven pounds)

• Can live for 150 years or more!

• Most of the population is subtidal but may find them at a 0m tide


• The Heart Cockle Clinocardium sp.

• Shallow burrowers• Most bivalves are

sedentary but some can escape by running away


• The swimming scallop Chlamys sp.

• Some bivalves can swim too.• Some have sensory cells for

light along the mantle

Phylum MolluscaSquid and Octopus - Class Cephalopoda

• The record breakers– The largest– The fastest– The smartest

Octopus sp.

Phylum Mollusca Squid - Class Cephalopoda

• The market squid

Loligo sp.• 8 long arms and

two tentacles• Species schools in

large numbers in shallows to lay eggs



Loligo sp.• Have corneas over

their eyes• Live from 4 to 5

months as adults• During the day live at depths of

500m and return to surface at night to hunt



Loligo sp.

• They have

chromatophores– Cells that can expand or contract and

are mediated by muscles and are under neural control

Phylum Mollusca Octopus - Class Cephalopoda

• The giant pacific octopus Octopus sp.

• Have 8 arms but no tentacles

• A cartilaginous skull• Have

chromatophores


• The red octopus Octopus sp.

• Not only can they change colour they can mimic as well


• The giant pacific octopus Octopus sp.

• Reproduction– Separate sexes– Modified arm for

sperm transfer– Male dies after mating– Female dies when her

eggs hatch.


• Octopus are smart

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4. molluscs clams and octopus