Mollusks

1. Mollusks

2. Classification • Phylum – Molluska • “Mollis” – soft • 7 Classes

3. Characteristics • Body enclosed within mantle • Secretes calcareous shell or stiff structure • Mantle cavity • Ventral, muscular foot • Location • Mostly marine • Fresh water, land

4. Characteristics • All systems present • Digestive • Nervous • Reproductive • Circulatory/respiratory

5. Class Monoplacophora • Mono – single, Placo – shell, Phora – bearing • Living specimens found in 1950’s • Previously only fossils • Deep water • Found in trench off of Pacific coast of Costa Rica • Shows evidence of segmentation • Suggests relation to the annelids (segmented worms)

6. Class Aplacophora • A – without, Placo – shell • Deep ocean • Lack a head, foot, or mantle

7. Class Polyplacophora • Poly – many • Shell with 8 overlapping plates (valves) • Possess a radula • Tongue-like, spike-covered organ • Scrapes algae

8. Class Gastropoda • “Univalves” • Marine snails and sea slugs • Dorsal, coiled shell

9. Class Bivalva • Two-shelled mollusks • No head, whole body within mantel • Foot protrudes between valves

10. Class Cephalopoda • “Ceph” – head, “pod” – foot • Octopus (shell absent), squid (reduced shell) nautilus (coiled) • Foot modified into tentacles around mouth

11. Giant Squid

13. Nautilus