Today’s Objectives:

1. Today’s Objectives: • TSW list key characteristics of mollusks, including, but not limited to, • Major organs/organ systems • Major classes and representatives • Economic importance • Evolutionary history • Other major characteristics

2. Mollusks

3. New evolutionary steps • Protostomes, characters including • Trochophore larvae • Spiral cleavage • Schizocoelous coelom formation • Eucoelomate • Advanced brain (some classes)

4. Key characteristics • Head-foot • Visceral mass • Mantle & mantle cavity • True coelom only in cavities around • Heart • Nephridia • Gonads • True circulatory system • Radula often present

5. Gastropoda – Gut Foots • Includes snails, limpets, & slugs • Freshwater, marine, and terrestrial • Display torsion • Shell coiling • Move on mucus with cilia or use foot

6. Gastropod Feeding Methods • Use radula to scrape algae • Some radula modified to pierce prey • Protostyle in digestive cavity

7. Gastropod Respiration & Circulation • Gas exchange in mantle cavity • Can have 1 or 2 gills • Some have a siphon • Open circulatory system • Blood acts as a hydraulic skeleton

8. Gastropod Nervous System • Nerves concentrated into large ganglia • Most ganglia in head • Simple or complex eyes • Statocysts • Chemoreceptors

9. Gastropod Excretory System • Nephridium (nephridia – plural) • Ammonia is the primary waste product in aquatic species • Uric acid is the waste for terrestrial species

10. Gastropod Reproduction • Can be monecious or dioecious • Usually cross-fertilize inside the mantle cavity • First development of a penis • Marine gastropods produce a veliger larva

11. Economic Importance of Gastropods • Garden pests • Good eating – escargot • Major intermediate host for several nasty parasitic infections

12. Representative Gastropods • Nudibranchs – sea slugs • Helix pomatia – escargot • Garden slugs

14. Bivalvia – 2 Shells • Umbo • Hinge • Nacre – mother of pearl • Shell made of calcium carbonate

15. Bivalve Respiration & Circulation • Gills expanded into multi-layered sheets (lamellae) • Usually 2 siphons – incurrent & excurrent • Open circulatory system

16. Gastropod Feeding & Digestion • Labial palps filter food particles • Mucus food string • Crystalline style • Gastric shield

17. Bivalve Nervous System • Ganglia located in esophagus, foot, and adductor muscle • Most sense organs located in margin of mantle (some have eyes there too) • Statocysts • Chemoreceptors

18. Bivalve Reproduction • Most are dioecious, some monoecious • Gonads in visceral mass • Fertilization usually external

19. Bivalve Development • Trochophore larva • Veliger larva • Glochidium – often parasitic

20. Bivalve Economic Importance • Often used as food • Pearl production • Invasive species – zebra mussel

21. Representative Bivalves • Mytilus – common mussel • Pinctada – pearl oysters • Dreissena polymorpha – zebra mussel

23. Cephalopoda – Head Foots • Octopi, squid, nautili, cuttlefish • Tentacles • Jet Propulsion • Closed Circulatory System

24. Cephalopoda Shell • External on nautili • Internal in squid (pen) • Internal in cuttlefish (cuttlebone) • Absent in octopi

25. Cephalopoda Locomotion • Use siphon for jet propulsion • Squeeze mantle cavity forcefully • Sometimes have external “wings” or fins for steering or slow locomotion • Nautili use internal air for neutral buoyancy

26. Cephalopoda Feeding • Most capture prey by sight • Use arms or tentacles to grab (sometimes have hooks and suckers) • Bring prey to beaked mouth • Muscular digestive system • Digestion in stomach and cecum • Anus near the funnel

27. Cephalopoda Respiration & Circulatory Systems • Closed ciculatory system – more efficient • 3 hearts • High metabolic rates • Respiration through gills

28. Cephalopoda Nervous System • Complex brains • Very advanced, large eyes • Statocysts • Touch receptors • Chemoreceptors • Chromatophores – color changing, signalling • Some bioluminescent • Ink gland

29. Cephalopoda Reproduction & Development • All are dioecious • Males have testes and package sperm in spermatophores • Fertilization mostly internal in back of female’s mantle cavity • Octopi have external fertilization of eggs • Often males have hectocotylus • All larval development inside eggs.

30. Economic Importance of Cephalopods • Research on nervous system • Bait • Food – calamari • Minerals for pets – cuttlebone

31. Representative Cephalopods • Loligo – common squid • Architeuthis dux – giant squid • Octopus dofleini – Giant pacific octopus

33. The Vampire Squid from Hell!!!!

34. Polyplacophora – Many Plate Bearing Animals • Used for food – hard to chew • Chitons • Crawl over floor using muscular foot • Can roll into a ball for protection • Most feed on algae • Ladderlike nervous system

35. Chiton

36. Scaphopoda – Boat feet • Often called “tusk shells” • Burrowing animals • Conical shell open at both ends • Often feed on foraminiferans • Dioecious

37. Monoplacophora – One Plate Bearing Animals • Dioecious • Considered living fossils • Neopilina • Live in deep ocean

38. Caudofoveata – Animals with Tails in Small Pits • Wormlike • Deep sea floor dwellers • Spicules on body wall

39. Aplacophora – No Plate Bearers • Also called solenogasters • Lack a shell • Nervous system similar to flatworms • Live on corals • Carnivores