Mollusks

Mollusks

Classification

• Phylum – Molluska– “Mollis” – soft– 7 Classes

Characteristics

• Body enclosed within mantle– Secretes calcareous shell or stiff structure

• Mantle cavity• Ventral, muscular foot

• Location– Mostly marine– Fresh water, land

Characteristics

• All systems present– Digestive– Nervous– Reproductive– Circulatory/respiratory

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)

Class Aplacophora

• A – without, Placo – shell• Deep ocean• Lack a head, foot, or mantle

Class Polyplacophora

• Poly – many• Shell with 8 overlapping plates

(valves)• Possess a radula– Tongue-like, spike-covered organ• Scrapes algae

Class Gastropoda

• “Univalves”• Marine snails and sea slugs• Dorsal, coiled shell

Class Bivalva

• Two-shelled mollusks• No head, whole body within mantel– Foot protrudes between valves

Class Cephalopoda• “Ceph” – head, “pod” – foot• Octopus (shell absent), squid (reduced shell)

nautilus (coiled)• Foot modified into tentacles around mouth

Giant Squid

Nautilus