1. Phylum Mollusca

2. Mollusks 100,000 species “soft bodied animals” Eumatazoans, bilaterally symmetrical, triploblastic coelomates Mostly marine, some freshwater, some terrestrial Size: microscopic snails to giant squids (largest invertebrate) Diverse group with varied appearances but similar body plans: Diverse ◦ Foot ◦ Visceral mass ◦ Mantle  Mantle cavity ◦ Shell ◦ Radula ◦ Siphon(s) Body systems

3. Characteristics Visceral Mass - contains the organs ◦ the “soft bodied” part Mantle – fold of tissue that drapes over the visceral mass makes shell in most organisms Internal or external Mantle cavity – water-filled chamber ◦ Contains gills, anus, and excretory pores Foot - muscular lower part used for movement Radula – sharp, tongue-like structure Head area is clearly defined ◦ contains the brain and sense organs

4. SYSTEMS Digestive – Complete gut Muscle – foot (for locomotion) Nervous (brain & nerve cords) ◦ Complex senses  Eye spots (light)  Chemical sensors/touch sensors (tentacles) Circulatory ◦ Blood vessels deliver oxygenated blood around the body (open system – blood mixes in coelom) ◦ Pumped by heart Respiratory – gills (aquatic)/lungs (on land) ◦ Siphons (move/pump water) ◦ Filter water Reproductive ◦ Ciliated larval stage (trochophore)

5. Nervous system and sense structures Gastropods: eye spots (on stalks at base of tentacles or on tentacles) and chemical sensors in tentacles Bivalves: photoreceptor and vibration cells Cephalopods: Best developed brain of all invertebrates- can detect light, vibrations, chemicals *Eye of snail* *Suckers on octopus tentacles*

6. Basic Body Plan

7. Shell vs. No Shell

8. Classes Class Aplacophora - 320 species ◦ Exclusively marine ◦ Burrowers ◦ No shell Class Bivalvia (clams, mussels, scallops, & oysters) Class Cephalopoda (squids & octopuses) Class Gastropoda (slugs & snails) Class Monoplacophora – 11 species ◦ Discovered in 1952 ◦ Many repeated organs (like annelids) ◦ Single shell Class Polyplacophora (chitons) Class Scaphopoda

9. 900 species Tusk shell Burrow on sea floor sediments Shell opened at both ends

10. Class Polyplacophora 600 species of Chitons Entirely marine species ◦ Inhabit rocky ocean bottoms and coastlines No head Oval body divided into 8 dorsal plates ◦ Body is unsegmented Foot used for movement and suction Feeds on algae

11. Class Gastropoda 3/4 th of all living species of mollusks “stomach-foot” Slugs and snails (move over slimy film) Slugs Marine, freshwater, and terrestrial Asymmetrical body plan Defined head with eyes and tentacles Usually have a single coiled shell ◦ Defense/safety ◦ Can be reduced or absent Open circulatory system Torsion: visceral mass rotates 180° causing the mantle cavity to be above its head (sea snails) Host to many parasites (zombie snails)zombie snails Eat algae & plants, or hunters (cone snail)cone snail ◦ Specialized radula

13. Sea snail Snail Slug Sea Slug

14. Class Bivalvia 15,000 species “2 door ways” Clams, oysters, mussels, and scallops Clamsscallops No distinct head, no radula Have two shells ◦ Attached at a hinge (by ligament) ◦ Adductor muscles open/close shells Gills in mantle cavity for respiration an ◦ Incurrent siphon – water in ◦ Excurrent siphon – water out Typically sessile suspension feeders (mussels have attaching threads) ◦ Can move with foot (clams) or “flapping” (scallops)scallops Some have eyes and sensory tentacles extending from mantle Reproduce through spawning (releasing sperm and egg) ◦ Seasonal

16. Oysters Mussels Scallops Clams

18. Bivalve Anatomy

19. Class Cephalopoda 700 species Octopi, squids, cuddle fish, chambered nautiluses Active, marine predators ◦ Beak like jaws (modified or absent radula) ◦ Some poisonous “head foot” Head (clearly defined) surrounded by grasping tentacles ◦ Modified foot ◦ Usually has suckers Shell can be internal (squids), external (chambered nautilus), or absent (octopi) Locomotion by jet propulsion (siphon) Only mollusk with a closed circulatory system Complex brain and sensory equipment (complex eyes)/nervous system (octopi – smartest invertebrate)octopi Chromatophores → color changing skin

20. OCTOPUS 8 tentacles ◦ Complete with suckers Intelligent hunters Intelligenthunters Can fit into tiny spaces ◦ No shell Masters of disguise Reproduction “intimate” and dangerous – male sometimes eaten Solitary and aggressive towards other members of their species Would you eat one?

21. Beak is surrounded by tentacles ◦ Sharp for tearing into prey (crabs, small fish, etc.)crabs Ink sack for defense against predators 3 hearts (2 for pumping blood through gills, 1 for pumping blood through body)

22. SQUID Internal shell Predators (squid feeding)feeding ◦ Beak ◦ Feeding tentacles Vampire squid Giant squid

24. CUDDLEFISH Excellent at camouflage ◦ Can change the color and texture of skin

25. CHAMBERED NAUTILUS CHAMBERED NAUTILUS Most primitive cephalopod Approx. 90 tentacles ◦ No suckers Grows shell in chambers Coloration helps avoid predators Eye has no lens Hunts with chemical sensors Hunts