1. Phylum Mollusca

2. Phylum Mollusca (mollis, soft)
Body usually an anterior head, ventral foot and a dorsal visceral mass.
Covered by a fleshy outgrowth of the body wall called a mantle.
Shell if present is secreted by the mantle
Radula- a tongue-like structure bearing transvers rows of minute chitinous teeth.
Good phylum for demonstrating Adaptative Radiation.
With the exception of Monoplacophora, the phylum is unsegmented.

3. Systems
Skeletal- Mantle may secretes a shell. Use hydrostatic pressure for ventral muscular foot.
Muscles -Ventral muscular foot and other muscles present.
Digestive- complete complex with salivary glands, digestive gland and Rasping tongue (Radula).
Circulatory - Open except for Cephalopoda. Dorsal heart, usually in a pericardial cavity.
Respiratory - Ctenidia (gills) in mantle cavity, respiratory pigment is copper.

4. Systems
Excretory- by nephridia usually connecting to the pericardial cavity,
the coelom is usually reduced to the cavities of the nephridia, gonads and pericardium.
Nervous - Nerve ring with various pairs of ganglia—two pairs of nerve cords, one innervating the foot, the other the visceral mass (modified ventral ladder-like system)
Integumentary - Mantle
Endocrine - nervous systems produces hormones.
Reproductive - varied- monoecious, protandric, or dioecious. Larva in marine = trochophore and veliger, in freshwater clam is glochidium.

5. Taxonomy Classes: Monoplacophora (no specimens) Polyplacophora
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Classes:
Monoplacophora (no specimens)
Polyplacophora
Scaphopoda
Gastropoda
Bivalvia
Cephalopoda

6. Class Polyplacophora (Chitons)
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Class Polyplacophora (Chitons)
Elliptical body with dorsal surface bearing eight overlapping limy plates (valves)
Chitons are marine.
They live mostly in shallow water.
All are similar in morphology and ecology.
They are slow moving microphagous feeders, scraping algae and other small invertebrates from substrate with their radula.
Genera
Katherina
Cryptochiton

7. Polyplacophora representative genera.
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Polyplacophora representative genera.
Katherina
Katherina dorsal surface
Katherina ventral surface

8. Polyplacophora representative genera.
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Polyplacophora representative genera.
Cryptochiton
Cryptochiton dorsal surface
Cryptochiton ventral surface

9. Class Scaphopoda Tooth shells (or Tusk shells) Dentalium
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Tooth shells (or Tusk shells)
Shell and mantle slender, tubular, and slightly curved. It is open at both ends
Dentalium

10. Class: Gastropoda Return to Taxonomy
Univalves, Shell usually spiral, distinct head, scraping radula.
Visceral mass typically turned 180° counterclockwise = torsion. And the visceral mass is coiled in shell.
Representatives
Garden snail (Helix), Whelks (Busycon), Conch, Cowries,, Sea hare, Nudibranchs, Slugs, and abalone.

11. Helix (garden snail) Return to Gastropoda Helix, ventral view
Helix, dorsal view
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Helix, side view

12. Busycon (Whelk) Return to Gastropoda Busycon (shell removed)
Busycon shells
Busycon eggs

13. Other Gastropods Return to Gastropoda Abalone shells Conch
Examples of gastropoda

14. Other Gastropods (continues)
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Other Gastropods (continues)
Sea Hair side view
Sea Hair (ventral view)
Slug

15. Class Bivalvia Return to Taxonomy
Shell of two lateral valves, with dorsal hinge.
Mantle of flattened right and left lobes. Posterior margin commonly forming siphons
Labial palps beside mouth
No head
No radula
Representative bivalves

16. Representatives of Bivalvia
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Representatives of Bivalvia
Anadonta (Freshwater clam)
Teredo (Shipworm)
Rock boring clam
Ostrea (Oyster)
Pecten (Scallop)
Freshwater clam dissection

17. Return to Representatives
Anadonta
Dissection

18. Teredo (shipworm) and the Rock boring worm
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Teredo (shipworm) and the Rock boring worm
Teredo
Teredo in wood
Rock boring clam

19. Oyster and Scallop Return to Representatives Scallop shells
Oyster cluster
Oyster shells

20. Freshwater Clam Dissection
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Freshwater Clam Dissection
External shell
Mantle
One mantle flap removed.
Visceral Mass (not dissected)
Dissected Visceral Mass I
Dissected Visceral Mass II
Dorsal Heart
Dorsal heart I(showing auricle or atrium)
Dorsal heart II(showing ventricle)
Dorsal heart III (ventricle)
Internal shell (showing muscle scars and pallial line)

21. Return to contents
External Shell

22. Return to contents
Mantle

23. One side of mantle removed
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One side of mantle removed

24. Return to contents
Visceral Mass

25. Dissected Visceral Mass (I)
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Dissected Visceral Mass (I)

26. Dissected Visceral mass (II)
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Dissected Visceral mass (II)

27. Return to contents
Dorsal Heart I

28. Dorsal Heart II
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29. Return to contents
Dorsal Heart III

30. Internal parts of shell Shell
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Internal parts of shell Shell
Pallial line

31. Class Cephalopoda Return to Taxonomy Large head with conspicuous eyes
Ventral foot modified into tentacles(are arms) with suckers.
Representative Cephalopods
Nautilus(Chambered Nautilus)
Octopus (Octopus)
Loligo (Squid)
Sepia (Cuttle fish)

32. Return to Cephalopoda
Nautilus
(South Pacific and Indian Ocean)

33. Return to Cephalopoda
Octopus
Eight arms

34. Return to Cephalopoda
Loligo
Internal skeleton = Pen

35. Return to Cephalopoda
Sepia
Cuttlebone (internal skeleton)

36. Class Monoplacophora Return to Taxonomy
First 10 specimens of Neopilina were taken in 1952 from dark muddy clay at 3350 m(11,000 ft) off the coast of Costa Rica.
Since then other species have been found in Indo-Pacific and South Atlantic Oceans.
Neopilina is the only living genus
Neopilina has segmented muscles