the bivalves
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Anatomy• Two shells (valves)
held together tightly by adductor muscles
• No head, brain is a set of nerve cells (ganglia)
• Gills to take oxygen from water
• Mantle secretes the shell
• Bilateral symmetry
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Class Bivalvia – The Bivalves(clams, mussesls, scallops, oysters)
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Habitat• Benthic– Most Sessile, few motile– Infauna – most burrow
down– Epifauna – some live on
seafloor• Mussels attach with
byssal threads• Scallops swim by
clapping shells together
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Feeding-Most are planktivores-Incurrent & excurrent Siphons-Important filter feeders-up to 25 gallons of water/day
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Bivalve Reproduction
-Separate sexes-External fertilization and development
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Pearl Formation• Mostly in oysters• Protection against
parasites or grains of sand
• Often not round• Natural pearls are
more costly• Cultured pearls are
made by inserting an object in the oyster
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