1. Phylum Mollusca

2. Mollusc Characteristics
90,000+ living species
70,000+ fossil species
Mantle
Pair of dorsal folds of the body wall
Forms a mantle cavity
Modified into gills or lungs
Secretes shell
Coelom
Limited to area around heart

3. Mollusc Characteristics (continued)
Muscular Foot
Variously adapted for locomotion
Radula
Odontophore - supporting cartilage of the radula

4. Mollusc Characteristics (continued)
Open Circulatory System
Trocophore larva
Veliger sometimes follows trocophore

8. Class Polyplacophora Chitons ~ 1000 species 7 or 8 dorsal plates
Numerous gills found in the mantle cavity

9. Chiton Anatomy

11. Class Scaphopoda Tusk Shells ~ 900 species Tubular tusk shaped shell
Captacula - mucus-covered, ciliated tentacles

12. Scaphopod Anatomy

13. Class Gastropoda
Snails, slugs, limpets, whelks, conchs, periwinkles, sea slugs, sea hares, and sea butterflies
~ 70,000 species
Well developed head
Large flat foot
Torsion - during development some body parts rotate relative to the mouth and head
Coiling - the shell is coiled and typically conispiral

14. Gastropod Anatomy

15. Gastropod Torsion

16. Evolution of Shell Coiling in Gastropods

17. Conispiral shells are either right-handed (dextral) or left-handed (sinistral)

24. Figure: 16_34b
Title:
Gastropod mollusks
Caption:
(b) Spanish shawl sea slugs prepare to mate.

27. Gastropod Eggs

28. Class Bivalvia Mussels, Clams, Scallops, Oysters, and Shipworms
~ 15,000 species
Two-lobed mantle
Two valves
Hatchet shaped foot
Head is greatly reduced
Most are filter feeders

29. Bivalve Anatomy

30. Bivalve Gills

31. Bivalve Hinge Ligament and Adductors

32. Bivalve Development

33. Glochidium Larvae of Freshwater Clams

35. Figure: 16_35b
Title:
Bivalve mollusks
Caption:
(b) Mussels attach to rocks in dense aggregations exposed at low tide. White barnacles are attached to the mussel shells and surrounding rock.

41. Class Cephalopoda
Nautiluses, Ammonoids (extinct), Squids, Cuttlefishes, and Octopuses
~ 700 species
Well-developed head with a brain and complex eye
Foot modified into funnel and arms/tentacles
Shell reduced or absent
Ink glands in all except Nautiloids
Chromotophores present

43. Nautilus Anatomy

44. Squid Anatomy

46. Figure: 16_36b
Title:
Cephalopod mollusks
Caption:
(b) The squid moves by contracting its mantle to generate jet propulsion, which pushes the animal backward through the water.

47. Cephalopod Eyes

50. Figure: 16_36a
Title:
Cephalopod mollusks
Caption:
(a) An octopus can crawl rapidly by using its eight suckered tentacles. It can alter its color and skin texture to blend with its surroundings. In emergencies this mollusk can jet backward by vigorously contracting its mantle.