Perch Dissection

Perch Dissection Name: ____________________ Section: ___ Lab Partner: _______________ Date: ________ Introduction: The fish in the group Osteichthyes have bony skeletons. There are three groups of the bony fish — rayfinned fish, lobe-finned fish, and the lung fish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage &/or bone to support them. Fins help the perch to move quickly through the water and steer without rolling. The perch also has a streamline 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 of the fish. Perch have powerful jaws and strong teeth for catching and eating prey. Yellow perch are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms. Perch move about in schools, often numbering in the hundreds. The scientific name for the yellow perch, most often used in dissection, is Perca flavescens (Perca means "dusky"; flavescens means "becoming gold colored"). The sides of the yellow perch are golden yellow to brassy green with six to eight dark vertical saddles and a white to yellow belly. Yellow perch have many small teeth, but no large canines. Yellow perch spawn from mid-April to early May by depositing their eggs over vegetation or the water bottom, with no care given. The eggs are laid in large gelatinous adhesive masses. Pre-Lab Questions (1 pt each): What type of skeleton do perch have ? Where in the water column do perch feed primarily? What is the scientific name for yellow perch? Materials: Preserved perch, dissecting pan, scalpel, scissors, forceps, slides, dissecting microscope, dissecting pins, apron, gloves, eye cover, tape measure (or yarn and ruler) Open the perch’s mouth and observe its bony jaws. Locate the upper jaw or maxilla and the lower jaw or mandible . Label the bold terms on Figure 1. Feel the inside of the mouth for the teeth. Locate & label the tongue & teeth on Figure 1. Open the mouth wider and use a probe to reach back to the gill chamber. Locate the nostrils and label on Figure 1. Locate and note the location of the eyes . Label on Figure 1. Find the bony covering on each side of the fish’s head called the operculum . The opercula cover & protect the gills. Label these on Figure 1. Figure 1 – External Perch anatomy (12 pts) Use a probe to lift the operculum and observe the gills. Note the color of the gills: ________________________________ (1 pt). Use a scissors to cut away one operculum to view the gills. Find the gill slits or spaces between the gills. Use your scalpel to carefully cut out one gill. Place the gill on a slide. Observe the gill under the dissecting microscope. Find the cartilage support called the gill arch and the soft gill filaments that make up each gill. The gill rakers prevent debris from entering the gills. Label the parts of the gill in Figure 2. Figure 2 – Gill Structure (3 pts) Observe the different fins on the perch. Locate the pectoral , dorsal , pelvic , anal , and caudal fins . Note whether the fin has spines . Label these on Figure 1 and complete Table 2 on fins. Table 2 – Fins (5 pts) Name of Fin Spines (yes or no) Number of Fins Find the lateral line on the side of your perch. Label this line on Figure 1. Use forceps to remove a few scales from your fish. Location Function Place the scales on the slide side by side (not stacked on top of each other). Observe the s cales under the dissecting microscope . Sketch a scale on Figure 3. Figure 3 – Structure of a Scale Your Sketch of a Scale (1 pt) Procedure (Internal Anatomy): Use dissecting pins to secure the fish to the dissecting pan. Use scissors to make the cuts through skin and muscle shown in Figure 4. Figure 4 – Cut Lines for Internal Dissection After making the cuts, carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity. In the upper part of the body below the lateral line is the swim bladder . This clear 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 male, there are two testes. In a female, there is only one ovary and it may be filled with eggs. Label the gonads on Figure 5. Based on the gonads, what is the sex of your fish? ___________________. (1 pt) Locate the cream colored liver in the front of the body cavity. Label th is on Figure 5. Remove the liver to observe the short esophagus attached to the stomach. Label the stomach on Figure 5 . At the posterior end of the stomach are the coiled intestines . Locate and then label these on Figure 5. Below the operculum, are the gill s . Locate these & them label them on Figure 5. In front of the liver & behind the gill s 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. Find the 2 long, dark kidneys in the dorsal posterior end of the perch. These filter wastes from the blood. Waste s exit the body through the anus located on the ventral side of the perch. Label this structure on figure 5. Figure 5 – Internal Perch Anatomy (8 pts) Questions & Observations: Answer these questions independently in your own words! 1. Does the perch have eyelids?(1 pt) 2. Are both jaws of the fish equally movable? Explain your answer. (2 pts) 3. Which fin was the largest? What other difference do you notice in this fin when it was compared to the others? (2 pts) 4. How many gill arches are located on each side of the perch? What covering protects them? (2 pts) 5. What is the function of the gill rakers? (1 pt) 6.. Explain how gas exchange occurs at the gills. What is the name of this process? (2 pts) 7. What is the function of the lateral line? (1 pt) 8. Explain how the swim bladder controls buoyancy. (2 pts) What are benefits in being made out of bone ? (2 pts) What advantages do cartilaginous fish have over boney fish? (2 pts) Lab Adapted from: Biology Junction