1. Phylum Mollusca
the “mollusks”

2. General Characteristics
Have a soft body sometimes enclosed in a shell
Have a ventrally located muscular foot used for movement
The larvae stage is called a trochophore – microscopic and free swimming often not resembling the adult
Considered coelomates – meaning they have a fluid filled body cavity (coelom)
Have a specialized organ called a radula which is used to scrape food off of hard surfaces

3. Feeding and Digestion
Members of this phylum are filter feeders, herbivores or active carnivores
All members have a one way gut with two openings
Bivalves are filter feeders using the siphon to gather water to filter
Gastropods tend to gather algae using their radula
Cephalopods are carnivores that capture their prey using their arms and tentacles and then chew up the prey using a hard beak found between the arms

4. Excretion
Have a complex excretion system that gathers waste in a nephridia (similar to our kidneys)
This system recovers water and nutrients and expels a concentrated waste product

5. Circulation and Respiration
Complex circulatory system that moves nutrients through the body
Most members have a three chambered heart
Marine mollusks have gills located in the mantle cavity

6. Reproduction Most members have distinct male and female sexual members
Some have the ability to change sexes between male and female
This helps keep the population high by providing the right ratio of male to female

7. Class Gastropoda Include snails, slugs, nudibranches and abalones
Range in size from microscopic to 1 meter
Most have a single shell but some have lost this shell completely like the slug and nudibranch
Most have tentacles on top of their head that contain simple eyes
Often a source of food for humans
Most are herbivores

9. Class Bivalves Examples are clams, mussels and oysters
The body is laterally compressed with two shells that are hinged at the bottom
Gills are used not only for respiration but also to filter debris out of the water for feeding
Strong muscles are used to open and close the shell
Have sense organs on the edge of the mantle that respond to light and touch

11. Class Bivalves cont.
Some have siphons which are used to bring oxygen to the bivalve that is buried in the sand; allows buried organisms to filter feed
They have byssal threads which they use to attach themselves to hard surfaces
Pearls are produced by oysters or clams – the pearl is basically the same material that the shell is made of:
It forms around a piece of sand, debris or irritation that has gotten into the body cavity and is irritating the clam

13. Class Cephalopods
Characterized as strong predators that specialized in movement
Group includes octopus, squids, cuttlefish and nautilius.
Most are active swimmers that have a vestigial shell present, but reduced in size and not used by the animal
Movement is achieved by bringing water into the funnel and pushed out the siphon
The funnel is a muscular part of the foot found under the head
The siphon is another tube that is flexible and moveable to help steer the squid
Foot is modified into tentacle with sucker discs to capture prey

14. Class Cephalopoda
Octopuses have eight arms and range in size between 2 inches and 30 feet
Squid have eight arms and two long tentacles and range in size between a few inches to more than 65 feet
All members of this class squirt ink if disturbed – this acts as a smoke screen to hide them from predators
the members of this class have a well defined brain and are capable of complex behaviors as seen in the movie “incredible suckers”