CLAM DISSECTION LAB
Purpose: http://www.youtube.com/watch?v=C-3GqvLswc8 dissection
pearl farm in china http://www.youtube.com/watch?v=NK9roDel3yE
PHYLUM : MOLLUSK
BIVALVES: CLASS PELYCOPODA :
MEANS HATCHET FOOT
• Describe the appearance of various organs found in a clam
• Name the organs that make up systems of the clam
• to differentiate between the classes with in the phylum
• To observe the external and internal characteristics of a clam
Materials: • safety goggles, gloves, screwdriver, magnifying glass, a lab apron, plastic zip lock bag, preserved clam, pen, dissecting tray, paper towels, scissors, forceps, dissecting needle, and dissecting pins.
BACKGROUND: Clams are bivalves, meaning that they have shells consisting of two halves, or valves. The valves are joined at the top, and the adductor muscles on each side hold the shell closed. If the adductor muscles are relaxed, the shell is pulled open by ligaments located on each side of the umbo. The clam's foot is used to dig down into the sand, and a pair of long incurrent and excurrent siphons that extrude from the clam's mantle out the side of the shell reach up to the water above (only the exit points for the siphons are shown). Clams are filter feeders. Water and food particles are drawn in through one siphon to the gills where tiny, hair-like cilia move the water, and the food is caught in mucus on the gills. From there, the food-mucus mixture is transported along a groove to the palps (mouth flaps) which push it into the clam's mouth. The second siphon carries away the water. The gills also draw oxygen from the water flow. The mantle, a thin membrane surrounding the body of the clam, secretes the shell. The oldest part of the clam shell is the umbo, and it is from the hinge area that the clam extends as it grows.
1. Put on your lab apron, safety glasses, and plastic gloves.
2. Place a clam in a dissecting tray and identify the anterior and posterior ends of the clam as well as the dorsal, ventral, & lateral surfaces.
3. Locate the umbo, the bump at the anterior end of the valve. This is the oldest part of the clam shell. Find the hinge ligament which hinges the valves together and observe the growth rings.
4. Turn the calm with its dorsal side down and insert a screwdriver between the ventral edges of the valves. Carefully work the tip of the screwdriver between the valves so you do not jab your hand.
5. Turn the screwdriver so that the valves are about a centimeter apart. Leave the tip of the screwdriver between the valves and place the clam in the pan with the left valve up.
6. Locate the adductor muscles. With your blade pointing toward the dorsal edge, slide your scalpel or scissors between the upper valve & the top tissue layer. Cut down through the anterior adductor muscle, cutting as close to the shell as possible.
7. Repeat step 6 in cutting the posterior adductor muscle.
8. Bend the left valve back so it lies flat in the
9. Run your fingers along the outside and the inside of the left valve and compare the texture of the two surfaces.
10. Examine the inner dorsal edges of both valves near the umbo and locate the tooth like projections. Close the valves & notice how the tooth like projections interlock.
11. Locate the muscle "scars" on the inner surface of the left valve. The adductor muscles were attached here to hold the clam closed.
12. Identify the mantle, the tissue that lines both valves & covers the soft body of the clam. Find the mantle cavity, the space inside the mantle.
13. Locate two openings on the posterior end of the clam. The more ventral opening is the incurrent siphon that carries water into the clam and the more dorsal opening is the excurrent siphon where wastes & water leave.
14. With probe lift the mantle so you can see the gills, respiratory structures.
15. Observe the muscular foot of the clam. Note the hatchet shape of the foot used to burrow into mud or sand.
16. Locate the palps, (mouth flaps) structures that surround & guide food into the clam's mouth. Beneath the palps, find the mouth.
17. With scissors, cut into the ventral portion of the foot. Cut the muscle at the top of the foot into right and left halves.
18. Carefully peel away the muscle layer to view the internal organs.
19. Locate the spongy, yellowish reproductive organs.
20. Ventral to the umbo, find the digestive gland, a greenish structure that surrounds the stomach.
21. Locate the long, coiled intestine extending from the stomach.
22. Follow the intestine through the calm. Find the area near the dorsal surface that the intestine passes through called the pericardial area. Find the clam's heart in this area.
23. Continue following the intestine toward the posterior end of the clam. Find the anus just behind the posterior adductor muscle.
24. Use your probe to trace the path of food & wastes from the incurrent siphon through the clam to the excurrent siphon
When you have finished dissecting the clam, dispose of the clam as your teacher advises and clean, dry, and return all dissecting equipment to the lab cart. Wash your hands thoroughly with soap.http://www.umanitoba.ca/faculties/science/zoology/faculty/hann/z260/images/clam.jpg
FILL IN THE DATA TABLE BELOW
||Digestive||opening for food|
||respiratory||inhalant tube brings in food and water|
|respiratory||exhalant tube that allows wastes to be removed|
||excretory||filters liquid waste|
||muscular||digs and moves clam|
||excretory||opening for wastes|
POSTERIOR ADDUCTOR MUSCLE
||skeletal||makes the shell and pearls|
||digestive||makes enzymes that break down food|
||digestive||guides food into mouth|
||respiratory||oxygen and carbon dioxide exchange; cilla filter feeds|
|nerves sends and recieves message|
||skeletal||the start of the shell-the oldest part|
||digestive||guides food to stomach|
||digestive||breaks down and absorbs food|
|R. GONADS (SEX
||reproductive||produces sex cells|
||digestive||breaks down food|
A. Answer the questions on your lab report.
B. Using the words in the above table label the following diagrams of the clam.
C. Use arrows on the clam diagram to trace the pathway of food as it travels to the clam's stomach. Continue the arrows showing wastes leaving through the anus.
Name the CLAM PHYLUM __MOLLUSK________________it
means SOFT BODIED
Name the CLAM CLASS _____PELEYCOPODA______________ it means HATCHET FOOT
GASTROPODA (means)___STOMACH FOOT_____________ EXAMPLE___SNAILS, SLUGS_______________
CEPHLOPODA (means)___HEAD FOOT_____________ EXAMPLE ___OCTOPUSES, SQUID, NAUTILUS_______________
LIST ALL THE SYSTEMS IN THE CLAM and explain their function 9pts
Again label the parts of the clam
Explain filter feeding in a clam. 3pts
Explain: HOW A PEARL IS FORMED? 3pts
Clams are known as filter feeders because of the way they eat their food. Since they have no heads or biting mouthparts, they have to feed in an unusual way. They pull water -- which also contains food particles -- in through one of their syphons and into their gills. The cilia in the clams' gills is able to trap the tiny food particles from the water and move them down to their mouth, where they can be eaten and digested. The water is then pushed out through the other syphon.
HOW A PEARL IS FORMED (VIDEO)