gastropods, bivalves,cephelapods 3 GENERAL BODY REGIONS 1. head- with “brain” or sense organs 2. visceral mass- contains internal organs 3. foot-

gastropods, bivalves,cephelapods

3 GENERAL BODY REGIONS 1. head- with “brain” or sense organs 2. visceral mass- contains internal

organs 3. foot- muscular part of body

Soft body in CaCO3 shell secreted by mantle

Body is bilaterally symmetrical Ventral muscular foot for locomotion Radula- rasping tongue, ribbon of small

teeth used to feed on algae “breathe” through gills

HI I’M GARY!

I’M SPONGE BOB’S PET SNAIL!

The radula is a rasping, protrusible feeding structure found in most molluscs (not bivalves). Ribbon-like

membrane with rows of tiny teeth.

The shell of a gastropod is always one piece – univalve – and may be coiled or uncoiled. The apex contains

the oldest and smallest whorl.

Shells may coil to the right or left – this is genetically controlled.

Early gastropods had a planospiral shell where each whorl lies outside the others. Bulky

Conispiral shells have each whorl to the side of the preceding one. Unbalanced

Shell shifts over for better weight distribution.

Many snails can withdraw into the shell and close it off with an operculum.

SNAILS

LIMPETSABALONE

NUDIBRANCH (sea slugs) gastropods that have lost their shell

CONE SNAIL (car nivorous)

CONCH

Clams, oysters, mussels Laterally compressed body enclosed in

two shells(valves) joined at a hinge, controlled by strong muscles

Gills used for getting 02 and filter feed No head or radula

CLAMS- use foot to burrow in sediment. Uses siphon to draw in water for O2 and food.

Largest bivalve- giant clam up to 3ft in length! (Tridacna gigas)*symbiotic zooxanthella help its size

OYSTERS- cement their shells to a hard surface, sometimes to other oysters

MUSSELS- not burrowers, secrete strong byssal threads to attach to surfaces

SCALLOPS- some can swim by ejecting water rapidly out siphon

GEODUCK

PEARL OYSTERS- when there’s an irritant or parasite in the mantle, shiny layers of nacre coats it to form pearl in some

* Most pearls we encounter are cultured pearls

Scallops have a row of small blue eyes along the mantle edge.

Native freshwater clams in the U.S. are jeopardized. Of more than 300

species once present, 12 are extinct, 42 are endangered and 88 more are of concern.

Sensitive to water quality changes,

Zebra mussels are a serious exotic invader into the Great Lakes Region.

Octopuses, squids, cuttlefish Active lifestyles, agile swimmers Complex nervous system, eyes similar

to ours Reduction/loss of shell Foot is modified into tentacles/arms

with suckers

Last living type of externally-shelled cephalopod

Don’t exhibit many other squid/octopus-like qualities

“Swimming snail”

“Jet-propulsion” of water, controlled by flexible siphon, for quick movement

Fans out body in defense

OCTOPUSES- 8 long arms, lack shell, bite prey (crabs, lobsters, shrimp) with beak-like jaws

Distract predators by emitting cloud of dark fluid produced by ink sac

SQUID- better swimmers, elongated body, two triangular fins, 8 arms and two tentacles w/suckers circling mouth, shell reduced to stiff pen

Colossal squid- largest invertebrate, hooks on tentacles

GIANT SQUID: up to 60ft in length, teeth on suckers.

CUTTLEFISH: have calcified internal shell that helps in bouyancy and gives its shape (cuttle bone)

Look like squid but have fin running along sides

Chromatophores-Red, brown, yellow pigments under skin controlled by muscles

Light reflectors under skin Muscles able to change texture