1. Polyplacophora Gastropoda Bivalvia Cephalopoda
Mollusks
Polyplacophora
Gastropoda
Bivalvia
Cephalopoda

2. Eucoelomates

3. Trochophore Larva
Many mulloscs start as free swimming trochophore larva
Larava pass through an intermediate stage called veliger

4. Basic Anatomy

5. Body Plan Head/Foot Visceral Mass Mantle
Sense organs, locomotion, mouth
Visceral Mass
Organ systems
Mantle
Secretes shell
Gaseous exchange (gills or lungs)

6. Radula Rasping tongue Scrapes food from surface Pulls food into mouth
Drills holes into shells

7. Class Polyplacophora Chitons Shell made of plates Organs
Three chambered heart
2 kidneys
Mouth and anus open at opposite ends

8. Polyplacophora Body Plan

9. Class Gastropoda Snails, abalone, slugs, nudibranchs, limpets
Slow moving predators or herbivores
Organ systems
Gills in most, some have lungs
Single kidney
Ganglia
Some are hermaphrodites
Coiling and torsion of visceral mass

10. Gastropoda Body Plan

11. Gastropoda Torsion

12. Gastropoda Coiling

13. Class Bivalvia Clams, muscles, scallops Organ systems
Laterally compressed
Shell in two halves, hinged
Suspension feeders
Organ systems
Three chambered heart
Three small ganglia
Scallops have multiple complex eyes

14. Bivalvia Feeding

15. Bivalvia Body Plan

16. Ship Worms
Bivalves that burrow into wood

17. Shipworm Specialized burrowing shell on one end
Filter feeders – also eat wood fibers (not directly)
Siphons
Burrowing Shell

18. Class Cephalopoda Octopus, squid, nautilus Organ systems
Foot developed into tentacles
Very mobile predators
Organ systems
Highly advanced brain and eyes
Closed circulatory system

19. Nautilus Anatomy

20. Squid Anatomy

22. Cephalopod Eye
Develops from ectoderm
Convergent evolution

23. Taningia danae
Largest light producing squid - ~2 meters (7 ft)

24. Taningia danae Grips prey with rows of hooks – not suckers
Eats fish and other squid

25. Architeuthis dux
Largest invertebrate - ~18 meters (60 feet)

26. Architeuthis dux Catches prey with double row of spiny suckers
Eats fish and other squid