Molluscs. Study Guide. Mollusc Characteristics. Coelom reduced Most viscera concentrated in dorsal visceral mass Body covered by thick mantle (epidermis) which forms a cavity Mantle secretes calcium carbonate shell (or spicules) Large ventral muscular foot
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Molluscs Study Guide
Mollusc Characteristics • Coelom reduced • Most viscera concentrated in dorsal visceral mass • Body covered by thick mantle (epidermis) which forms a cavity • Mantle secretes calcium carbonate shell (or spicules) • Large ventral muscular foot • Radula (band of teeth in esophagus)
Class Bivalvia — Clams, etc. • Body and foot laterally compressed • Shell with two hinged valves • Reduced cephalization • Edges of mantle usually fused to form siphons • Radula lost • Marine and freshwater; mostly filter-feeders
Kingdom: Animalia Phylum: Mollusca Class: Pelecypoda Order: Eulamellibranchia Family: Veneridae Genus:Venus Species: mercenaria
Practice Slides The next few slides have no labels. Practice using the following clam dissections.
Internal features of the clam; the shell and mantle have been removed to show the foot and gills (ctenidia).
Internal anatomy of the clam, showing mouth, stomach, intestine, heart, pericardial cavity and musculature.
Internal features of the clam. The foot has been opened to show the digestive system and gonads.
Pericardial cavity of the clam showing the heart and the intestine passing through it. The atrium of the heart is visible.
Internal anatomy of the clam showing the posterior region. The cavity above the gills leading to the excurrent siphon is visible.
View of the siphons of the clam. The incurrent is lower and the excurrent is uppermost. (WHY?) The shell on the left side has been removed.
Class Cephalopoda — Squid, etc. • Shell chambered (if present), reduced, or absent • Prehensile tentacles surround mouth • Mouth with radula and beak • Muscular siphon provides jet propulsion • Well developed brain, eyes • Closed circulatory system • Marine
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Order: Teuthida Family: Loliginidae Genus: Loligo Species: brevipenna
Notes • Arms are for prey capture and transfer of sperm to female by male. • Tentacles are for holding prey after it is captured. • The pen is the remnant of what feature of most molluscs? • What are chromatophores used for?