1. Mollusks Chapter 27

2. Mollusk characteristics Soft-bodied animals with an internal or external shell Trochophore: free-swimming larvae stage Body plan –Foot: crawling, burrowing, tentacles –Mantle: thin tissue layer that covers body –Shell: made from glands that secrete calcium carbonate, may be reduced or lost in some –Visceral mass: internal organs

3. Section 27-4 Shell Mantle cavity Foot Gills Digestive tract Snail Early mollusk Clam Squid The Mollusk Body Plan Figure 27–21

6. Feeding Herbivores, carnivores, filter feeders, detritivores, parasites Siphon: tubelike structure where water enters and leaves the body, washing water over gills and trapping plankton

7. Radula flexible, tongue- shaped structure with tiny teeth for drilling through shells or scraping algae off rocks Hypselodoris bilineata

8. Digestive system

9. Respiration Gills within mantle cavity Large surface area with blood vessels Orange peel nudibranch (about 25 cm length) with protruding white gills on the ventral side

10. Circulation Circulatory system to carry oxygen, nutrients, & waste Open circulatory system

11. Excretion and Reproduction Nephridia: tube shaped structures remove ammonia from blood Release waste outside of body Sexual reproduction External fertilization

12. Laying squid eggs

13. Response Clams and other bivalves live sedentary lives and have simple nervous systems. Cephalopods have highly developed nervous systems. octopus eye

14. Movement Snails: secrete mucus and crawl slowly Cephalopods: fast moving, drawing water into mantle cavity and forcing water out of siphon (like jet propulsion) excessive amount of snail mucus secreted

15. Snail mucus trail

16. Groups of mollusks Gastropods: shell-less or single-shelled mollusks with muscular feet Sea snail

17. Mexican turbo snail

18. Nudibranch sea slug

20. Groups of mollusks Bivalves: two shells held together by one or two powerful muscles

21. Section 27-4 Mouth Shell Stomach Coelom Heart Nephridium Adductor muscle Anus Excurrent siphon Incurrent siphon Gills Mantle cavity Foot Intestine Mantle cavity Adductor muscle The Anatomy of a Clam Figure 27–23

24. Groups of mollusks Cephalopods: soft-bodied mollusks where the head is attached to a foot, divided into arms and tentacles

25. Squid

26. Octopus

27. Cuttlefish

28. Vampire squid

29. Octopus eye

30. Nautilus