The document describes key characteristics of the phylum Mollusca. It includes information on their anatomy, physiology and taxonomy. Some key points are: - Molluscs are soft-bodied or shelled animals including snails, slugs, clams, squid and octopuses. - They have a mantle, visceral mass, and in most cases a shell secreted by the mantle. - Major classes include gastropods, bivalves, cephalopods, chitons and others. - Life cycles typically involve a trochophore larva, veliger larva and indirect development to adulthood.

1. Phylum MolluscaPhylum Mollusca

2. Phylum MolluscaPhylum Mollusca
 ProtostomesProtostomes
 Lophotrochozoan groupLophotrochozoan group
 Eucoelomates (coelomates)Eucoelomates (coelomates)
Tridacna squamosa
Tridacna gigas

3. Phylum MolluscaPhylum Mollusca
 Soft BodiedSoft Bodied
 ShelledShelled
 Some withoutSome without
 CephalizationCephalization
 Sensory organsSensory organs
 MouthsMouths
 Body DivisionsBody Divisions
 Visceral MassVisceral Mass
 Head-FootHead-Foot
 MantleMantle
Tonicella lineata

4. Phylum MolluscaPhylum Mollusca
 Complete digestive tractComplete digestive tract
 Digestive glandsDigestive glands
 Specialized feedingSpecialized feeding
structuresstructures
 Circulatory systemCirculatory system
 Heart (2 chambers)Heart (2 chambers)
 Open system in mostOpen system in most
groupsgroups
 Closed in cephalopodsClosed in cephalopods
 Coelom restricted to pericardium in most casesCoelom restricted to pericardium in most cases
Octopus briareus

5. Phylum MolluscaPhylum Mollusca
 Advanced nervous systemAdvanced nervous system
 BrainBrain
 Sensory organsSensory organs
 Eyes (simple and camera)Eyes (simple and camera)
 Sensory papillaeSensory papillae
 Excretory systemExcretory system
 Kidney-like nephridiaKidney-like nephridia
 ReproductionReproduction
 Monoecious and dioeciousMonoecious and dioecious
 External developmentExternal development
 External & internalExternal & internal
fertilizationfertilization

6. Mollusc PhylogenyMollusc Phylogeny
 ~50-80K extant~50-80K extant
speciesspecies
 ~40K extinct~40K extinct
speciesspecies
 Fossil recordsFossil records
from precambrianfrom precambrian
period ofperiod of
proterozoic eonproterozoic eon
(>570my BP)(>570my BP)

7. MolluscMollusc
PhylogenyPhylogeny
 Mantle secretingMantle secreting
shellshell
 Muscular footMuscular foot
 Chambered heartChambered heart

8. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
ChitonsChitons
Chiton tuberculatusChiton tuberculatus lives inlives in
the rocky intertidal zonesthe rocky intertidal zones
eat algae with its radulaeat algae with its radula
8 shell plates8 shell plates

9. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
Subclasses:Subclasses:
ProsobranchiaProsobranchia
 Shelled marineShelled marine
gastropodsgastropods
Atlantic triton’s trumpetAtlantic triton’s trumpet
((Charonia variegataCharonia variegata))
Tiger cowrie (Tiger cowrie (Cypraea tigrisCypraea tigris))

10. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
Subclasses:Subclasses:
 ProsobranchiaProsobranchia
OpisthobranchiaOpisthobranchia
 Sea slugs (marine)Sea slugs (marine) zebra sea goddesszebra sea goddess
((Hypselodoris zebraHypselodoris zebra))
Spotted sea hare (Spotted sea hare (Aplysia dactylomelaAplysia dactylomela
Phidiana hiltoni

11. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
Subclasses:Subclasses:
 ProsobranchiaProsobranchia
 OpisthobranchiaOpisthobranchia
PulmonataPulmonata
 TerrestrialTerrestrial
snails/slugssnails/slugs
 FreshwaterFreshwater
snailssnails
Helminthoglypta walkeriana
Giant banana slug
(Ariolimax columbians)

12. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
 BivalviaBivalvia
 Clams, oysters,Clams, oysters,
mussels, scallopsmussels, scallops
Bay scallop (Aequipecten irradians)
Edible mussels
(Mytilus edulis)
Ostrea edulis

13. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
 BivalviaBivalvia
 CephalopodaCephalopoda
 Octopus, squid, nautilusOctopus, squid, nautilus
Giant cuttlefish (Giant cuttlefish (Sepia latimanusSepia latimanus))
Nautilus sp
Octopus sp

14. Mollusc TaxonomyMollusc Taxonomy
 Major classesMajor classes
 PolyplacophoraPolyplacophora
 GastropodaGastropoda
 BivalviaBivalvia
 CephalopodaCephalopoda
 Minor classesMinor classes
 MonoplacophoraMonoplacophora
 SolenogastresSolenogastres
 CaudofoveataCaudofoveata

15. Generalized Mollusc AnatomyGeneralized Mollusc Anatomy

16. Gastropod FeedingGastropod Feeding
ApparatusApparatus

17. Respiration: GillsRespiration: Gills

18. Shell Structure & FormationShell Structure & Formation

19. A Pearl Among the SwineA Pearl Among the Swine

20. Mollusc Reproduction & DevelopmentMollusc Reproduction & Development
 Indirect developmentIndirect development
 Larval stagesLarval stages
 Trochophore larvaTrochophore larva
 Free swimming, ciliated, shell formation beginsFree swimming, ciliated, shell formation begins
 Veliger larvaVeliger larva
 Free swimming, ciliated velium forms,Free swimming, ciliated velium forms,
 Shell/body torsion occursShell/body torsion occurs
 SpatSpat
 Metamorphic form between veliger and juvenileMetamorphic form between veliger and juvenile
 Shell elaboratesShell elaborates

21. Trochophore LarvaTrochophore Larva

22. Gastropod Veliger LarvaGastropod Veliger Larva
Velia
Mouth
Shell

24. Zygote
Trochophore
Veliger
Spat
Juvenile
Adult

25. Adult AbaloneAdult Abalone

26. Class Polyplacophora - chitonsClass Polyplacophora - chitons

27. Polyplacophoran AnatomyPolyplacophoran Anatomy

28. ClassClass
GastropodaGastropoda
The Shell GameThe Shell Game

29. Class Gastropoda - TorsionClass Gastropoda - Torsion

30. Gastropod ShellGastropod Shell
CoilingCoiling

31. GastropodGastropod
Gill/Mantle CavityGill/Mantle Cavity
EvolutionEvolution

32. Generalized Gastropod AnatomyGeneralized Gastropod Anatomy

33. Marine GastropodsMarine Gastropods
Cowries

34. Marine GastropodsMarine Gastropods
Sea Hare – Aplysia sp

35. Marine Gastropods - NudibranchMarine Gastropods - Nudibranch

36. Terrestrial GastropodsTerrestrial Gastropods
- Pulmonata- Pulmonata
 The mantle cavity servesThe mantle cavity serves
as a “lung”as a “lung”
 Glandular epidermisGlandular epidermis
 Secrete mucus (slime)Secrete mucus (slime)
upon which gastropodupon which gastropod
glidesglides

37. Terrestrial Gastropod -Terrestrial Gastropod -
PulmonataPulmonata
 Slugs lackSlugs lack
shellsshells
 Mantle thickenedMantle thickened
 PneumostomePneumostome
 Air intake into mantle cavityAir intake into mantle cavity
PneumostomePneumostome

38. Phylum Mollusca, Class BilvaliaPhylum Mollusca, Class Bilvalia
 Two shellsTwo shells
 Incurrent & excurrent siphonsIncurrent & excurrent siphons
 No cephalizationNo cephalization

39. Generalized Bivalve AnatomyGeneralized Bivalve Anatomy

40. Generalized Bivalve AnatomyGeneralized Bivalve Anatomy
(XS)(XS)

41. Bivalve Anatomy (Sagittal)Bivalve Anatomy (Sagittal)

42. Bivalves are Typically Filter FeedersBivalves are Typically Filter Feeders

43. Bivalve Life CycleBivalve Life Cycle

44. Glochidia – Unique Larval Stage ofGlochidia – Unique Larval Stage of
Freshwater BivalvesFreshwater Bivalves
 Internal fertilizationInternal fertilization
 Early development in broodEarly development in brood
chamber (region of mantlechamber (region of mantle
cavity)cavity)
 Release of glochidia veligerRelease of glochidia veliger
larvaelarvae
 Glochidia attach to gills ofGlochidia attach to gills of
fish and are distributedfish and are distributed

45. Phylum Mollusca, Class CephalopodaPhylum Mollusca, Class Cephalopoda
 Closed circulatory systemClosed circulatory system
 Shell: lost in Octopus, extremely reduced andShell: lost in Octopus, extremely reduced and
enclosed in mantle in squid, planar spiral inenclosed in mantle in squid, planar spiral in
NautilusNautilus
 CephalizationCephalization
 eyeeye
 Beak aroundBeak around
mouthmouth
 Tentacles/armsTentacles/arms

46. Cephalopod AnatomyCephalopod Anatomy

47. Squid are the largestSquid are the largest
CephalopodsCephalopods

48. Nautilus AnatomyNautilus Anatomy

49. Cephalopod EyeCephalopod Eye

50. MatingMating

51. Direct Development in CephalopodsDirect Development in Cephalopods

52. Color & Morphology Changes forColor & Morphology Changes for
CamouflageCamouflage