1. Kingdom Animalia, Phylum Mollusca (means “soft”)
Mollusks
Kingdom Animalia, Phylum Mollusca (means “soft”)

2. What is a Mollusk? Soft body with internal or external shell
Ex: snails, slugs, clams, squids, and octopi
Trochophore larva

3. Body plan: Foot – takes on many forms Mantle – covers the body
Shell – (present in most), made
by glands in the mantle
Visceral mass – internal organs

4. Feeding: Herbivores, Carnivores Filter feeders (clams,
Oysters, scallops)
Parasites
Many feed using a flexible tongue shaped structure called a radula. (snails, slugs)

5. Respiration:
Aquatic mollusks – snails, clams – breathe using gills in the mantel cavity
Land snails breathe with a “lung” – a mantle cavity with a large surface area and many blood vessels.

6. Circulation – can be open or closed
Open works better for slow moving mollusks (less efficient)
Closed works better for fast moving mollusks (more efficient)
Excretion – tube shaped nephridia
Response – nervous systems vary from simple to complex
Reproduction – many reproduce sexually with external fertilization,
Tentacled mollusks this is usually internal
A few are hermaphrodites
All have a free swimming trochophore larva !

7. Groups of Mollusks 1. Gastropods 2. Bivalves 3. Cephalopods
Three major classes of mollusks
1. Gastropods
2. Bivalves
3. Cephalopods

8. Gastropod snails, slugs, and nudibranchs Shell-less or single shelled
Move by a muscular foot
Some are poisonous, bright colors

9. Snail

10. Slug

11. Nudibranchs (sea slugs)
Check out the nudibranch gallery at nationalgeographic

12. Bivalves (things with 2 shells)
Such as clams, scallops

13. Cephalopods octopi, squids, cuttlefish, and nautilus
soft-bodied , head is attached to foot
foot is divided into tentacles with sucking disks
small internal shells or no shell at all

14. Cuttlefish (the chameleon of the sea)

15. Nautilus is only cephalopod with shell
Squid have a modified shell called a pen
Well developed eyes
most complex of the mollusks

16. Octopus (creeps on tentacles)

18. Squid

19. Octopus versus Shark