1 Dissection of the Clam Venus mercenaria copyright cmassengale

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1 Dissection of the Clam Venus mercenaria copyright cmassengale Slide 2 2 Slide 3 3 Taxonomy of Bivalve Mollusks Kingdom Phylum Class Genus Species Animalia Mollusca Bivalvia Venus mercenaria copyright cmassengale Slide 4 4 Bivalve Mollusks Soft bodies invertebrates Have a muscular foot that can be extended for movement Two part, hinged shell Complete, one-way digestive tract with a mouth & anus Separate sexes copyright cmassengale Slide 5 5 Bivalve Mollusks No eyes or distinct head Have siphons to circulate water through their bodies Filter feed on plankton Mussels are large and have a flat, more oblong shell shape, while freshwater clams are smaller (3/4 inch) and typically more round copyright cmassengale Slide 6 6 Indirect Development Goes through a free- swimming, larval stage called the trochophore Adults move slowly by their extendable foot copyright cmassengale Slide 7 7 Bivalve Mollusks Protostomes blastopore becomes the mouth Have a fully lined body or mantle cavity Body organs called visceral mass protected by mantle which secretes the shell Open circulation Most are sessile or sedentary Includes clams, oysters, scallops, & mussels copyright cmassengale Slide 8 8 Bivalves Slide 9 9 Slide 10 10 External Anatomy copyright cmassengale Slide 11 11 Bivalve Shell Umbo is the raised, oldest part of the shell and is used to find surfaces Dorsal Ventral Anterior Posterior UMBO copyright cmassengale Slide 12 12 Bivalve Shell Shell show regular spacing of external growth rings on shells and their progressive crowding as the animals grow older Growth Rings copyright cmassengale Slide 13 13 Bivalve Shell Bivalves have an incurrent and excurrent siphon to bring in water containing food & O 2 and for excess water & wastes to leave Siphons copyright cmassengale Slide 14 14copyright cmassengale Slide 15 15 The hinge ligament holds the two halves of the shell together Bivalve Shell copyright cmassengale Slide 16 16 Internal Anatomy copyright cmassengale Slide 17 17 Scissor tips or a screwdriver & can be used to open the shell copyright cmassengale Slide 18 18 Adductor Muscles Strong adductor muscles help open & close the valves and must be cut to examine the interior of the clam copyright cmassengale Slide 19 19copyright cmassengale Slide 20 20 Inside Shell Lining The inside of the shell is pearly and smooth to protect the body Oysters coat irritants with a substance called mother of pearl copyright cmassengale Slide 21 21copyright cmassengale Slide 22 22 Teeth located on the dorsal edge of the shell lock to keep shells from sliding copyright cmassengale Slide 23 23 The mantle makes a CaCO 3 (limestone) shell copyright cmassengale Slide 24 24 Mantle cavity Gills hang outside visceral mass (body) in the mantle cavity & remove O 2 as H 2 O flows over them Gills copyright cmassengale Slide 25 25copyright cmassengale Slide 26 26copyright cmassengale Slide 27 27copyright cmassengale Slide 28 28 Water Flow Incurrent siphons aid in bringing in water with food and oxygen Cilia direct water into the gills, while labial palps direct water into the mouth Cilia on the gills pulls in water move food toward the mouth copyright cmassengale Slide 29 29 VISCERAL MASS - contains respiratory, digestive, & reproductive systems copyright cmassengale Slide 30 30 HEART & PERICARDIAL CAVITY copyright cmassengale Slide 31 31 Nervous System Consists of 3 pairs of ganglia (brain) Has 2 pairs of nerve cords extending from this copyright cmassengale Slide 32 32 Nitrogen waste from kidney Digestive waste from anus Sperm or egg (if external fertilization) Larva (if internal fertilization) Released into Mantle Cavity to be removed by excurrent Siphon: copyright cmassengale Slide 33 33copyright cmassengale Slide 34 34copyright cmassengale