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Pygmy Perch Dissection
Perch are members of the class Osteichthyes, the bony fish.
Fins help the perch move quickly through the water and steer without rolling. Overall, the shape of the perch's body could be described as streamlined, and it is built to move easily through the water. In addition, one important difference between bony and cartilaginous fish is that bony fish possess a swim bladder. This swim bladder gives the fish buoyancy, and it allows them to sink/rise in the water - it also regulates the concentration of oxygen in the fish's blood. Perch have strong jaws, as well as teeth for capturing prey.
Preserved perch, dissecting pan, scalpel, scissors, forceps, magnifying glass, dissecting pins, apron, gloves, eye cover, ruler
PROCEDURE - INTERNAL ANATOMY
1. Use dissecting pins to secure the fish to the dissecting pan. Use scissors to make the cuts through skin and muscle as shown in the figure below. Start at the cloaca, and be sure to cut through the ribs. Try to keep the swim bladder intact as you cut.
2. After making the cuts, carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity.
3. Locate the liver in the front of the body cavity. Label this on Figure 5.
4. At the posterior end of the stomach are the coiled intestines. Locate and then label these on Figure 5.
5. Find the small reddish brown spleen near the stomach and label this on Figure 5.
6. Below the operculum, are the bony gill rakers. Locate these & them label them on Figure 5.
7. In front of the liver & behind the gill rakers is the pericardial cavity containing the heart. The heart of a fish only has 2 chambers --- an atrium & and a ventricle. Locate the heart & label it on Figure 5.
In the upper part of the body below the lateral line is the swim bladder. This sac has a thin wall and gives the fish buoyancy. Label the swim bladder on Figure 5.
Below the swim bladder are the gonads, testes or ovaries. In a female, these may be filled with eggs. Label the gonads on Figure 5.
10. Find the 2 long, dark kidneys in the posterior end of the perch. These filter wastes from the blood. Label the kidneys in Figure 5
11. Wastes exit the body through the cloaca located on the ventral side of the perch. Label this structure on figure 5.
12. After you have identified the internal organs, show them to Mr. Hampton (liver, heart, stomach, intestine, reproductive organs, spleen).
13. You should attempt to find the brain -start your cut about 1/2 inch behind the fish's eyes forward towards the snout. Be sure to angle your scissors up in order to try to preserve the brain.
RESOURCES TO AID IN IDENTIFYING ANATOMY
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