1. PHYLUM MOLLUSCA

2. Phylum Mollusca 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

3. Class Gastropoda (stomach-footed)
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

4. HI I’M GARY!
I’M SPONGE BOB’S PET SNAIL!

6. Head-Foot Region
The radula is a rasping, protrusible feeding structure found in most molluscs (not bivalves).
Ribbon-like membrane with rows of tiny teeth.

7. Class Gastropoda
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.

8. Class Gastropoda
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.

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

10. ABALONE SNAILS LIMPETS CONCH
NUDIBRANCH (sea slugs) gastropods that have lost their shell
CONE SNAIL (car nivorous)

11. Class bivalvia 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

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

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

14. SCALLOPS- some can swim by ejecting water rapidly out siphon
MUSSELS- not burrowers, secrete strong byssal threads to attach to surfaces
OYSTERS- cement their shells to a hard surface, sometimes to other oysters
SCALLOPS- some can swim by ejecting water rapidly out siphon
GEODUCK

15. 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

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

17. Class Bivalvia 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.

18. Class cephalopoda (“head-footed”)
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

19. Nautilus Last living type of externally-shelled cephalopod
Don’t exhibit many other squid/octopus-like qualities
“Swimming snail”

20. “Jet-propulsion” of water, controlled by flexible siphon, for quick movement
Fans out body in defense

21. 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

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

23. Colossal squid- largest invertebrate, hooks on tentacles
GIANT SQUID: up to 60ft in length, teeth on suckers.

24. CUTTLEFISH: have calcified internal shell that helps in bouyancy and gives its shape (cuttle bone)
Look like squid but have fin running along sides

25. CAMOUFLAGE
Chromatophores-Red, brown, yellow pigments under skin controlled by muscles
Light reflectors under skin
Muscles able to change texture