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