1. Phylum Mollusca 75000 species 2nd only to Phylum Arthropoda
Includes octopuses, oysters, snails, slugs, squids, clams…
Divided into 6 classes based on shell and foot

3. Common Characteristics
Shell ~ tough multilayered structure, for protection or body support
Mantle ~ sheath of tissue that encloses vital organs, secretes its shell and forms its respiratory structures
Visceral hump ~ contains its heart, digestive, and excretory organs, covered by mantle
Foot ~ fleshy, muscular organ used for locomotion
Radula ~ small organ covered with tiny teeth that scrapes up food particles and draws them into mouth.
Trochophore- ciliated larval form

4. 3 Mollusk Classes Bivalvia – two shelled mollusks
Gastropoda - stomach footed mollusks
Cephalopoda – head footed mollusks

5. Clam Nutrition and Digestion
Filter feeders- feed on organic material strained from the water
Bivalves lack a radula
Siphons- tubes used to filter water over the clams body
Palps- pair of lobelike organs surrounding the mouth
Gills and palps secrete a stringy, sticky mucus that catches the food
Cilia move food to the mouth
Digestive system also includes a stomach, digestive gland, intestines, and anus

6. Class Bivalvia: Two-Shelled Mollusks
Clams, oysters, mussels, scallops

7. Clams
Clams secrete shiny material around an irritating foreign object forming a pearl
Foot is used for locomotion and burrowing
Can also move by rapidly opening and closing shell which causes it to bounce along the seafloor
Nervous system including ganglia, nerves, and various sensory organs including as many as 100 simple eyes along the margin of the valve that can detect light and movement
Sexual reproduction

9. Circulation and Respiration
Open circulatory system including a heart and a kidney which filters waste from the blood
Respiratory system including gills- thin walled ciliated structures richly supplied with blood vessels where oxygen and carbon dioxide are exchanged

11. Class Gastropoda: Stomach-Footed Mollusks
Snail, slugs, nudibranchs
The foot is immediately below the visceral hump which is where the stomach is located.
Nudibranch Videos

12. Nutrition and Digestion
Eats plant material
Scrapes food with tonguelike radula
Torsion- body develops into twisted, asymmetrical arrangement unique to gastropods, anus is close to anterior region of the body, above the mouth

13. Respiration Mantle cavity
space between the mantle lining, the shell, and the animal’s soft body
Thickly supplied with blood vessels and functions as a lung in respiration

14. Locomotion Lays down a layer of slime
Glides on slime by rhythmical contractions of its muscular foot (10ft per hour)

15. Response Series of ganglia around the head region
Pair of eyes at the end of two tentacles
Other receptors for smell, touch, and chemical detection located in the head and foot

16. Class Cephalopoda: Head-Footed Mollusks
Octopus, squid, nautilus, cuttlefish

17. Class Cephalopoda The foot extends from the head region
The foot is usually divided and contains suckers
Squids eyes are much like mammalian eyes and are capable of very accurate vision.
Amazing camouflage and mimicry abilities