Introduction The phylum Mollusca has snails, clams, chitons, slugs, limpets, octopi, and squid. Together mollusks develop from a fertilized egg come an adult, most pass with a larval stage dubbed the trocophore. The trocophore is a ciliated, free-swimming stage. Mollusks additionally have a radula or file-like body organ for feeding, a mantle that might secrete a shell, and also a muscular foot for locomotion. Clams are naval mollusks through 2 valves or shells. Prefer all mollusks, a clam has actually a mantle which surrounds its soft body. It additionally has a muscular foot which permits the clam come burrow itself in dirt or sand. The soft tissue above the foot is called the visceral mass and also contains the clam’s human body organs.

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Taxonomy Kingdom – Animalia Phylum – Mollusca course – Bivalvia or Pelecypoda

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Objective To examine the internal and also external anatomy that a bivalve mollusk.

Materials Dissecting pan, dissecting kit, screwdriver, laboratory apron, plastic gloves, safety and security glasses, maintained clam

Procedure

put on your lab apron, safety and security glasses, and also plastic gloves. Place a seashells in a dissecting tray and identify the anterior and posterior end of the clam and also the dorsal, ventral, & lateral surfaces. Figure 1

Figure 1

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find the umbo, the bump at the anterior finish of the valve. This is the oldest part of the clam shell. Discover the hinge ligament i beg your pardon hinges the valves together and also observe the growth rings.

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rotate the calm v its dorsal side down and also insert a screwdriver between the ventral edge of the valves. Carefully work-related the guideline of the screwdriver between the valves for this reason you perform not jab her hand.

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revolve the screwdriver so that the valves are about a centimeter apart. Leave the guideline of the screwdriver in between the valves and also place the clam in the pan through the left valve up. Find the adductor muscles. With your tongue pointing toward the dorsal edge, slide her scalpel between the upper valve & the top tissue layer. Cut down with the anterior adductor muscle, cutting as close to the covering as possible.

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Repeat action 6 in cutting the posterior adductor muscle. Number 2

Figure 2

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bend the left valve back so it lies flat in the tray. Run your fingers follow me the outside and the within of the left valve and also compare the structure of the two surfaces.

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research the inner dorsal edge of both valves close to the umbo and also locate the toothlike projections. Near the valves & notice how the toothlike projections interlock. Find the muscle "scars" on the inner surface ar of the left valve. The adductor muscles to be attached below to hold the shell closed. Recognize the mantle, the organization that lines both valves & consist of the soft human body of the clam. Discover the mantle cavity, the space inside the mantle.

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locate two openings on the posterior finish of the clam. The much more ventral opening is the incurrent siphon that carries water right into the clam and the an ext dorsal opening is the excurrent siphon wherein wastes & water leave.

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with scissors, closely cut far the half of the mantle the lined the left valve. After ~ removing this component of the mantle, you deserve to see the gills, respiratory tract structures. Watch the muscular foot the the clam, i beg your pardon is ventral to the gills. Note the hatchet shape of the foot used to burrow into mud or sand.

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find the palps, flaplike frameworks that surround & overview food into the clam’s mouth. The palps are anterior come the gills & ventral to the anterior adductor muscle. Beneath the palps, find the mouth.

Figure 3


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through scissors, cut off the ventral portion of the foot. Usage the scalpel to closely cut the muscle in ~ the top of the foot right into right and left halves. Carefully peel far the muscle class to check out the interior organs.

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locate the spongy, yellowish reproductive organs. Ventral come the umbo, find the digestive gland, a greenish structure that surrounds the stomach. Locate the long, coiled intestine prolonging from the stomach. Monitor the intestine v the calm. Uncover the area near the dorsal surface ar that the intestine passes through referred to as the pericardial area. Find the clam’s heart in this area.

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proceed following the intestine towards the posterior finish of the clam. Uncover the anus just behind the posterior adductor muscle. Use your probe to trace the course of food & wastes native the incurrent siphon through the clam come the excurrent siphon. Answer the concerns on your lab report & brand the diagrams the the inner structures the the clam. Also, use arrows top top the clam diagram to map the pathway that food as it travels to the clam’s stomach. Continue the arrows mirroring wastes leaving with the anus.

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When you have actually finished dissecting the clam, dispose that the clam as your teacher advises and clean, dry, and also return all dissecting devices to the rap cart. Wash her hands extensively with soap.