Name: Block: Due Date: Perch Dissection Lab Background The fish in the class Osteichthyes have bony skeletons. There are three groups of the bony fish: ray-finned, lobe-finned, and the lungfish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage and/or bone to support them. Fins help the perch to move quickly through the water and steer without rolling. The perch also has a streamlined body shape that makes it well adapted for movement in the water. All ray-finned fish have a swim bladder that gives the fish buoyancy allowing them to sink or rise in the water. The swim bladder also regulates the concentration of gases in the blood. Perch have powerful jaws and strong teeth for catching and eating prey. Perch are primarily bottom feeders. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the hundreds. Purpose To examine the internal and external anatomy of the perch. Procedure External Anatomy 1. Rinse your perch. 2. Label the anterior, posterior, dorsal, and ventral sides on Figure 1. 3. Label the 3 body regions of the perch head, trunk, and tail on Figure 1. 4. Open the mouth and observe its jaws. Label the upper jaw (maxilla) and the lower jaw (mandible) on Figure 1. 5. Feel inside the mouth for the teeth. 6. Open the mouth wide and use a probe to reach back to the gill chamber. 7. Label the eyes and nostrils on Figure 1. 8. Find the lateral line on the side of your perch. Label this line on Figure 1. Figure 1: External Perch Anatomy
9. Observe the different fins on the perch: pectoral, dorsal, pelvic, anal, and caudal fins. Label these on Figure 1 and complete Table 2: Fins. Table 2: Fins Name of Fin Spines (Y/N) # of Fins Location Function 10. Find the bony covering on each side of the fish's head called the operculum. The opercula cover and protect the gills. Label these on Figure 1. 11. Use a probe to lift the operculum and observe the gills. Note their color. 12. Use scissors to cut away one operculum to view the gills. Find the gill slits or spaces between the gills. 13. Use your scalpel to carefully cut out one gill. Find the cartilage support called the gill arch and the soft gill filaments that make up each gill. 14. Use forceps to remove a few scales from your fish. Observe the scales under the magnifying glass or microscope. Sketch a scale on Figure 3. Figure 3: Perch Scale Sketch
Internal Anatomy 1. Insert the tip of the scissors in the anus and cut toward the head, between the pelvic fins and just past the pectoral fins. Cut only through the skin, careful not cut any organs. Continue cutting through skin and muscle as in Figure 4. Figure 4: Cut lines 2. Carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity. 3. Locate the cream colored liver in the front of the body cavity. Label this in the table on the next page associated with Figure 5. 4. Remove the liver to observe the short esophagus attached to the stomach. Label the stomach in the table for Figure 5. 5. At the posterior end of the stomach are the coiled intestines. Label these in the table for Figure 5. 6. Label the operculum in Figure 5. Below the operculum are the bony gills. Locate these and label them in the table for Figure 5. 7. In front of the liver and behind the gills is the pericardial cavity containing the heart. The heart of a fish only has 2 chambers --- an atrium and a ventricle. Locate the heart and label it in the table for Figure 5. 8. In the upper part of the body cavity, below the lateral line is the swim bladder. This sac has a thin wall. Label the swim bladder in the table for Figure 5. 9. Below the swim bladder are the gonads (testes or ovaries). Label them in the table for Figure 5. 10. Find the two long, dark kidneys in the posterior end. Label the kidneys in the table for Figure 5. 11. Wastes exit the body through the anus located on the ventral side of the perch. Label the anus in the table for Figure 5. 12. Based on your knowledge from the previous sections of this lab, label the rest of Figure 5, using the associated table. Label the nostril, brain, spinal cord, all fins (dorsal, adipose, caudal, anal, and pelvic), and the lateral line.
Figure 5: Internal Perch Anatomy Label # Body Part Label # Body Part 1 11 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 10
Post-Lab Questions 1. Are both jaws of the fish equally movable? Explain your answer. 2. Does the perch have eyelids? 3. How many gills are located on each side of the perch? What covering protects them? 4. The tail end has no organs; it s all muscle. Why do you think that is? 5. Explain how gas exchange occurs at the gills. 6. Which fin was the largest? What other difference do you notice in this fin compared to the others? 7. What is the function of the lateral line? 8. Describe how the scales are arranged on the trunk and tail of your fish. 9. What is the function of the swim bladder? Explain how it works.