/20 Lab #5 The Dissection of the Perch

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1 /20 Lab #5 The Dissection of the Perch Perch are members of the class Osterichthyes, or bony fishes. They are found in many Canadian waters and are an excellent specimen of boney fish. Food enters the fishes mouth and passes through the stomach and into the intestine. Digestion is aided by bile produced by the liver, which is attached to the intestine. Solid waste passes out through the anus. Name: Section: Wastes from metabolism are processed by kidneys and pass out through the urogenital opening. Oxygen is obtained from the water as it passes over the gills. Waste carbon dioxide is passed into the water at the same time. Movement is achieved by the action of muscles attached to the bony skeleton of the fish and is guided by the action of several types of fins. The fish has an air bladder in its body to help it stay afloat. The amount of gas in the bladder is adjusted by gas exchange across the capillaries in the air bladder wall. The lateral line, found on the outside of the body, allows the fish to sense differences in pressure and to sense low-frequency sounds. In this lab, you will dissect a fish in order to observe the external and internal structures of fish anatomy. Purpose During this lab we will become familiar with the a species of boney fish and learn about the function of each organ within the fish. We will also hope to establish an understanding of the life- Materials - dissecting pins - dissection tray - preserved perch - dissection kit - gloves for dissection - ruler What to Do 1. Within your groups, send one member to the front to collect the supplies and your specimen to be dissected. 2. Using a ruler, measure the length of the fish you are studying. Record it in cm Fish Length 3. Place the fish on the dissection tray with the head on your left. Locate, and check off, the following structures. (There is a diagram to help you on the next page) Mouth Nostrils Eyes Operculum Lateral Line Dorsal Fins Caudal Fin Anal Fin Pelvic Fin Pectoral Fin anus Teeth

2 4. Using scissors, and the diagram (right) cut on one side from the corner of the mouth to the front lower edge of the operculum. Remove the operculum and examine the gills. Describe the texture and appearance of the gills 5. Use scissors to remove a gill, and identify the fingerlike gill filaments. On the inside of the fill are sturdy projections called gill rakers. They help keep food away from the gills. Note that the gills open directly into the throat. 6. Cut along the dotted line below with scissors, pulling up to ensure the organs below are not damaged.

3 7. Remove the portion of the body you have cut after you complete these incisions. Cut (a) Cut along the bello of the fish from the front edge of the operculum through the trunk to the anus Cut (b) Cut up along the side of the fish to the backbone Cut (c) Pin the fish on its side through the edge of the belly and tail. Lift open the side of the fish and cut forward through the ribs along the backbone to the tip of the operculum 8. Once your fish is open, locate the following internal organs: Air (swim) bladder stomach intestine kidneys gonads (ovaries or testes) liver heart (different chambers) muscles ribs vertebrae anus urogenital opening 9. Dispose of the fish into the garbage including all animal parts 10. Clean your pan and clean the tools using soap and water. Dry with paper towel. Have your station checked before you return to class. 11. Complete the analysis questions.

4 Analysis 1. What is the purpose of the lateral line in fish? 2. How is the lateral line related to the function of the human ear? 3. What organs that you observed connect to the urogenital opening? 4. What adaptations for life in the water did you observe in the perch? Name at least 2 and describe how they help the fish. 5. What is the purpose of the swim bladder? 6. Suggest why the perch is coloured the way it is (both the ventral and dorsal sides)

5 7. What is the function of the operculum? 8. What features of this fish act as a defense against predators 9. From the type of teeth that the Perch had, what level on the trophic pyramid do you predict it is on? 10. What are the myomeres and how do they help the fish swim? (on the Animals of the Pelagic Environment booklet) 11. Explain two [2] differences between chondrichthyes and osteichthyes fish classes.