1. Phylum Mollusca

14. Molluscan diversity

20. PoriferaPoriferaCycliophoraCycliophora CnidariaCnidaria CtenophoraCtenophora SipunculaSipuncula MolluscaMollusca AnnelidaAnnelida OnychophoraOnychophora TardigradaTardigrada BryozoaBryozoa PlatyhelminthesPlatyhelminthes NemerteaNemertea RotiferaRotifera GnathostomulidaGnathostomulida GastrotrichaGastrotricha NematodaNematoda NematomorphaNematomorpha PriapulidaPriapulida KinorhynchaKinorhyncha LoriciferaLoricifera PhoronidaPhoronida BrachiopodaBrachiopoda EchinodermataEchinodermata ChordataChordata HemichordataHemichordata ArthropodaArthropoda Adapted from Lesser Known Protostome Phyla. SICB 2001. J.R. Garey. Possess trochophore larvae Mollusca and Annelida are closely allied phyla

21. 93,000 species of described molluscs (extant) + 70,000 more species from fossil record Echinodermata Ciliophora Chordata Mollusca Platyhelminthes Nematoda Porifera Annelida Other Apicomplex Sarcomastigophora Arthropoda

22. Defining characteristics of Mollusca Bilateral symmetry, cephalization Coelom (around heart) Mantle –draped over viscera –secretes shell Complete digestive tract, Radula Trochophore larvae (often also veliger larvae) Locomotion by muscular foot Heart, liver, gills (ctenidia), kidney

23. Phylum. Mollusca Class. Aplacophora Class. Polyplacophora Class. Monoplacophora Class. Gastropoda Class. Cephalopoda Class. Bivalvia Class. Scaphopoda Phylum. Mollusca Class. Aplacophora Class. Polyplacophora Class. Monoplacophora Class. Gastropoda Class. Cephalopoda Class. Bivalvia Class. Scaphopoda

24. Aplacophora Polyplacophora Monoplacophora Gastropoda Cephalopoda Bivalvia Scaphopoda

25. Mollusc origins? Platyhelminthe-like ancestor with spicules on dorsal surface, cilia on ventral surface, and dorsoventral musculature.

26. Mollusc origins? Spicules fuse to form dorsal shell, cilia on ventral surface, and dorsoventral musculature.

27. Mollusc origins? Spicules fuse to form dorsal shell, cilia on ventral surface, dorsoventral musculature, gonads and excretory pores in mantle cavity

28. Mollusc origins? Spicules fuse to form dorsal shell, cilia on ventral surface, dorsoventral musculature, gonads, excretory pores, and ctenidia, in mantle cavity.

29. HAM: Hypothetical ancestral mollusc Mantle cavity CtenidiumCtenidium Pericardial cavity MetanephridiumMetanephridium RadulaRadula GonadGonad Stomach and digestive gland FootFoot

30. Dorsal mantle covers the visceral mass. Secretes the shell

31. Mollusc shell PeriostracumPeriostracum Prismatic layer Nacreous layer Mantle epithelium Mantle lobes

32. Pearl formation PeriostracumPeriostracum Prismatic layer Nacreous layer Developing pearl EpitheliumEpithelium

33. Ctenidium (Respiration)

34. Ctenidium (gill) InterlamellarjunctionsInterlamellarjunctions OstiumOstium FrontalciliaFrontalcilia Blood vessel ExhalentwaterExhalentwater

35. Paired ventral nerve cords

36. Complete digestive system

37. Radula

39. Aplacophora Gill folds MouthMouth Pedal pit Pedal groove

40. Class Aplacophora 320 spp, all marine No fossil record (!) & poorly studied Calcareous spines and scales in epidermis (no true shell) Radula used for grasping Burrow in the substrate Eat cnidarians

41. Polyplacophora

42. Mantle cavity MouthMouth CtenidiumCtenidium FootFoot AnusAnus

43. Polyplacophora MouthMouth DigestiveglandDigestivegland StomachStomachGonadGonad Pericardial cavity NephridiumNephridium AnusAnus

44. Polyplacophora The “chitons” 800 spp, marine Typically, shell = 8 dorsal plates Ctenidia use counter-current gas exchange Commonly encountered in the intertidal zone