1. Phylum Mollusca

2. Characteristics of Phylum Mollusca
Latin for “soft”
Bilaterally symmetrical
May have a shell composed of calcium carbonate secreted by the mantle.
Shell may be external, internal or absent
Muscular foot is used for movement
Some use radula (tongue) to feed

3. Class Aplacophora: Solenogasters and Chaetoderm
Approx. 288 species
Primitive. The class which other molluscs are believed to have evolved from
Worm-like molluscs with no shell.
Mostly deep-water inhabitants

4. Class Monoplacophora: Monoplacophorans
Approx. 11 species
Body covered by a shield-like shell
Primitive. Contains members very similar to gastropods

5. Class Polyplacophora: Chitons
Approx. 800 species
Flattened bodies, having the dorsal surface covered by eight shell plates.
Herbivores
Many are photosensitive

6. Class Gastropoda: Snails, Slugs and Nudibranchs
Approx. 30,000 species
Land, fresh and marine species
Usually identified by the presence of a shell
Herbivores and carnivores
Nudibranch
Nudibranch

7. Class Gastropoda: Snails, Slugs and Nudibranchs
Many have an operculum to seal off shell
Most have separate sexes; some are hermaphroditic
Use radula to feed
Wentletrap
Black Sea Hare

8. Radula (tongue)
Radula of a snail
Radula of an octopus

9. Snails
Triton’s Trumpet
Bubble snail

10. Nudibranchs (naked gills)
Glaucilla marginata
Hermissenda
Glaucilla marginata...eats
Portuguese-Man-of-War (Blue Bottles)
Spanish Shawl

11. Slugs Have internal gills and shells
Ink or have a bad taste for defense
Navanax

12. Class Bivalvia: Clams, Mussels
Approx. 15,000 species
Marine and fresh water species
Body is enclosed within two lateral shells (valves) that are hinged dorsally
Use gills for feeding and respiration
Clams
Mussels

13. Class Bivalvia: Scallops and Oysters
Strong adductor muscles draw two shells together for protection
Usually separate sexes, eggs and fertilized externally
Used commercially for food and jewelry
Scallop
Oysters
Scallops

14. Class Scaphopoda: Tusk Shell
Approx. 350 species
Burrowing molluscs having a tubular, tusk-like shell, open at each end
Gills absent
Filter feeders

15. Class Cephalopoda: Octopus, Squid, Nautilus and Cuttlefish
Approx. 600 species
All marine
Jet propulsion for swimming.
Well developed nervous system and brain = intelligent
8,10 or 24+ Sucker bearing tentacles
Carnivores
Able to change color and texture
Will ink when threatened

16. Chromatophores Can change color rapidly due to chromatophores.
Pigment cells controlled by the nervous system

17. Squid
Squid Beak

18. Nautilus
Living fossil

19. Cuttlefish

20. Octopus Blue ringed Octopus Blue Ringed
Mimic Octopus

21. Octopus
Giant Pacific Octopus
How many arms?