Mollusks
description
Transcript of 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