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Phylum Mollusca

Phylum Mollusca. Phylum Mollusca. Protostomes Lophotrochozoan group Eucoelomates (coelomates). Tridacna gigas. Tridacna squamosa. Phylum Mollusca. Soft Bodied Shelled Some without Cephalization Sensory organs Mouths Body Divisions Visceral Mass Head-Foot Mantle.

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Phylum Mollusca

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  1. Phylum Mollusca

  2. Phylum Mollusca • Protostomes • Lophotrochozoan group • Eucoelomates (coelomates) Tridacna gigas Tridacna squamosa

  3. Phylum Mollusca • Soft Bodied • Shelled • Some without • Cephalization • Sensory organs • Mouths • Body Divisions • Visceral Mass • Head-Foot • Mantle Tonicella lineata

  4. Phylum Mollusca Octopus briareus • Complete digestive tract • Digestive glands • Specialized feeding structures • Circulatory system • Heart (2 chambers) • Open system in most groups • Closed in cephalopods • Coelom restricted to pericardium in most cases

  5. Phylum Mollusca • Advanced nervous system • Brain • Sensory organs • Eyes (simple and camera) • Sensory papillae • Excretory system • Kidney-like nephridia • Reproduction • Monoecious and dioecious • External development • External & internal fertilization

  6. Mollusc Phylogeny • ~50-80K extant species • ~40K extinct species • Fossil records from precambrian period of proterozoic eon (>570my BP)

  7. Mollusc Phylogeny • Mantle secreting shell • Muscular foot • Chambered heart

  8. Mollusc Taxonomy Chiton tuberculatus lives in the rocky intertidal zones eat algae with its radula 8 shell plates • Major classes • Polyplacophora • Chitons

  9. Mollusc Taxonomy Atlantic triton’s trumpet (Charonia variegata) • Major classes • Polyplacophora • Gastropoda • Subclasses: • Prosobranchia • Shelled marine gastropods Tiger cowrie (Cypraea tigris)

  10. Mollusc Taxonomy Spotted sea hare (Aplysia dactylomela) • Major classes • Polyplacophora • Gastropoda • Subclasses: • Prosobranchia • Opisthobranchia • Sea slugs (marine) Phidiana hiltoni zebra sea goddess(Hypselodoris zebra)

  11. Mollusc Taxonomy Helminthoglypta walkeriana • Major classes • Polyplacophora • Gastropoda • Subclasses: • Prosobranchia • Opisthobranchia • Pulmonata • Terrestrial snails/slugs • Freshwater snails Giant banana slug (Ariolimax columbians)

  12. Mollusc Taxonomy Bay scallop (Aequipecten irradians) • Major classes • Polyplacophora • Gastropoda • Bivalvia • Clams, oysters, mussels, scallops Edible mussels (Mytilus edulis)

  13. Mollusc Taxonomy Giant cuttlefish (Sepia latimanus) • Major classes • Polyplacophora • Gastropoda • Bivalvia • Cephalopoda • Octopus, squid, nautilus Octopus sp Nautilus sp

  14. Mollusc Taxonomy • Major classes • Polyplacophora • Gastropoda • Bivalvia • Cephalopoda • Minor classes • Monoplacophora • Solenogastres • Caudofoveata

  15. Generalized Mollusc Anatomy

  16. Gastropod Feeding Apparatus

  17. Respiration: Gills

  18. Shell Structure & Formation

  19. A Pearl Among the Swine

  20. Mollusc Reproduction & Development • Indirect development • Larval stages • Trochophore larva • Free swimming, ciliated, shell formation begins • Veliger larva • Free swimming, ciliated velium forms, • Shell/body torsion occurs • Spat • Metamorphic form between veliger and juvenile • Shell elaborates

  21. Trochophore Larva

  22. Gastropod Veliger Larva Mouth Velia Shell

  23. Veliger Zygote Trochophore Juvenile Spat Adult

  24. Class Polyplacophora - chitons

  25. Polyplacophoran Anatomy

  26. Class Gastropoda The Shell Game

  27. Class Gastropoda - Torsion

  28. Gastropod Shell Coiling

  29. Gastropod Gill/Mantle Cavity Evolution

  30. Generalized Gastropod Anatomy

  31. Marine Gastropods Sea Hare – Aplysia sp

  32. Marine Gastropods - Nudibranch

  33. Terrestrial Gastropods - Pulmonata • The mantle cavity serves as a “lung” • Glandular epidermis • Secrete mucus (slime) upon which gastropod glides

  34. Terrestrial Gastropod - Pulmonata Pneumostome • Slugs lack shells • Mantle thickened • Pneumostome • Air intake into mantle cavity

  35. Phylum Mollusca, Class Bilvalia • Two shells • Incurrent & excurrent siphons • No cephalization

  36. Generalized Bivalve Anatomy

  37. Generalized Bivalve Anatomy (XS)

  38. Bivalve Anatomy (Sagittal)

  39. Bivalves are Typically Filter Feeders

  40. Bivalve Life Cycle

  41. Glochidia – Unique Larval Stage of Freshwater Bivalves • Internal fertilization • Early development in brood chamber (region of mantle cavity) • Release of glochidia veliger larvae • Glochidia attach to gills of fish and are distributed

  42. Phylum Mollusca, Class Cephalopoda • Closed circulatory system • Shell: lost in Octopus, extremely reduced and enclosed in mantle in squid, planar spiral in Nautilus • Cephalization • eye • Beak around mouth • Tentacles/arms

  43. Cephalopod Anatomy

  44. Squid are the largest Cephalopods

  45. Nautilus Anatomy

  46. Cephalopod Eye

  47. Mating

  48. Direct Development in Cephalopods

  49. Color & Morphology Changes for Camouflage

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