Epifaunal Bivalves• Their foot excretes tough threads that attach

organisms to rocks in order to prevent waves from washing them away.

• Mussels and Oysters do this but mussels attach to rock whereas oysters attach to each other and build reef structures.

Bivalve Morphology• Two valves are mirror shapes

of each other

• Made of aragonite (calcium carbonate)

• Two valves united dorsally (in the back) along the hinge line by a tough ligament

• Teeth and sockets interlock to prevent shearing between shells.

• Valves open ventrally (at the front).

Bivalve Morphology• Valves are secreted by mantle

lobes

• Attachment of mantle (organism) to shell is marked by the pallial line.

• Valves are closed by the contraction of a pair of adductor muscles.

• When adductor muscles relax, a ligament expands and the shell opens.

• Some bivalves have a pallial sinus showing they had a siphon.

Cephalopods• Cephalon means head, pod means foot• Most highly evolved mollusk• Includes marine predators such as nautiluses, octopuses,

and squid. • Have a head surrounded by a foot divided into tentacles. • Nautiluses have a coiled shell• Squid have a thin shell-type left over inside their bodies• Octopuses have evolved to completely get rid of a shell• Pelagic: Move by creeping on the ocean floor, swimming

with fins, or squirting jets of water.

Nautiluses• Like most cephalopods, they catch

their prey with stiff adhesive disks on their tentacles and tear or bite flesh with their beaks.

• Live in the open ocean and hunts at considerable depths. (5-550 meters)

• Pelagic Nekton lifestyle

• Carnivore and a scavanger

• They move up and down the water column with gas filled chambers (same way a submarine moves up and down). • Decrease air in chamber and you

sink. Increase air and float upwards.