CLAM DISSECTION LAB    NAME______________
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.

Image result for clam anatomyImage result for clam anatomy

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.

Procedure
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.

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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.  

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8. Bend the left valve back so it lies flat in the tray.
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.

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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

ORGAN SYSTEM FUNCTION 
A. MOUTH
 
Digestive opening for food
B. INCURRENT SIPHON
 
respiratory inhalant tube brings in food and water

C. EXCURRENT SIPHON
 

respiratory exhalant tube that allows wastes to be removed
D. HEART
 
circulatory pumps blood
E. KIDNEY
 
excretory filters liquid waste
F. FOOT
 
muscular digs and moves clam
G. ANUS
 
excretory opening for wastes
H. POSTERIOR ADDUCTOR MUSCLE
 
muscular closes shell
I. MANTLE
 
skeletal makes the shell and pearls
J. DIGESTIVE GLAND
 
digestive makes enzymes that break down food
K. MOUTH FLAPS
 
digestive guides food into mouth
L. SHELL
 
skeletal protection
M. GILLS 
 
respiratory oxygen and carbon dioxide exchange; cilla filter feeds
N. GANGLIA
 

nervous
nerves sends and recieves message
O. UMBO
 
skeletal the start of the shell-the oldest part
P. esophagus
 
digestive guides food to stomach
Q. INTESTINE
 
digestive breaks down and absorbs food
R. GONADS (SEX GLAND)
 
reproductive produces sex cells
S. ANTERIOR ADDUCTOR MUSCLE
 
muscular closes shell
T. STOMACH
 
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

SYSTEM FUNCTION
1.  
2.  
3.  
4.  
5.  
6.  
7.  
8.  

 

Again label the parts of the clam

Explain filter feeding in a clam. 3pts

 

 

Explain: HOW A PEARL IS FORMED?  3pts

 

 

FILTER FEEDING:

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)

There are essentially three types of pearls: natural, cultured and imitation.

Natural Pearls form when an irritant - usually a parasite and not the proverbial grain of sand - works its way into an oyster, mussel, or clam. As a defense mechanism, a fluid is used to coat the irritant. Layer upon layer of this coating, called 'nacre', is deposited until a lustrous pearl is formed.

A cultured pearl undergoes the same process. The only difference is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl. These 'seeds' or 'nuclei' are most often formed from mussel shells. Quality cultured pearls require a sufficient amount of time - generally at least 3 years - for a thick layer of nacre to be deposited, resulting in a beautiful, gem-quality pearl. Lower-quality pearls have often been 'rushed' out of the oyster too quickly (sometimes a year or less) and have a too-thin coat of nacre. 

Pearls can come from either salt or freshwater sources. Historically, saltwater pearls were rounder and had a better nacre than freshwater pearls, while freshwater pearls tended to be very irregular in shape, with a puffed rice appearance the most prevalent. However, improvements in freshwater pearl farming techniques have narrowed that gap, with freshwater pearls now exhibiting great roundness and deep luster.

The culturing process usually takes several years. Mussels must reach a mature age, which can take up to 3 years, and only then can be implanted or naturally receive an irritant. Once the irritant is in place, it can take up to another 3 years for the pearl to reach its full size and nacre thickness.  Of the pearls produced, only approximately 5% are of sufficient true gem-quality for top jewelry makers, yet a pearl farmer can figure on spending over $100 for every oyster that is farmed, whether a gem-quality pearl is produced or not.

Imitation pearls are a different story altogether. In most cases, a glass bead is dipped into a solution made from fish scales. This coating is thin and may eventually wear off. One can usually tell an imitation by rubbing it across the teeth: Fake pearls glide across your teeth, while the layers of nacre on real pearls feel gritty. The Island of Mallorca is known for its imitation pearl industry, and the term "Mallorca Pearls" or "Majorica Pearls" is frequently (though inaccurately) used to describe these pearl simulants.