Perch Dissection
Lab Write Up- In order to do the lab, you must label the attached diagrams of the perch and attach them in your lab
book. If you don’t have the diagrams done for the first day of the lab, you will take a 0 on this lab; there will be no
makeups.
Lab Procedure- To be followed in the lab (not written in the lab book)
External Anatomy
Locate all the external structures as shown in Figure 1 on your specimen.
Open the perch's mouth and observe its bony jaws. Feel the inside of the mouth for the teeth. Use a probe to lift the
operculum and observe the gills. Note their color. 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. Find the cartilage support
called the gill arch and the soft gill filaments that make up each gill. Use forceps to remove a few scales from your
fish. Observe the scales under the magnifying glass. Include a sketch in your lab notebook.
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Internal Anatomy
Figure 3 shows the incisions to be made for viewing the internal structures of the perch. Begin the incision along the
dorsal side of the fish no higher than the lateral line. Most of the organs reside in the ventral half of the fish’s body.
Be careful not to cut too deeply, you might destroy some of the internal organs.
Digestive System: Find the tan-colored liver with the gallbladder attached to and underneath the liver. Cut the liver
free from the body to expose the esophagus and stomach. Then, trace the route a piece of food would travel as it
passes through the fish’s digestive system. Find the mouth, pharynx, esophagus, pyloric caeca (blind ended sacs),
stomach, intestine, and anus. To aid in locating other organs, remove the entire digestive canal by cutting it free at
the anus and at the mouth.
Reproductive System - Determine if your fish is a male or female by locating either a pair of testes, small, pale
yellow masses on the ventral side or a single, large, yellow ovary filled with eggs. The testes and ovaries are
connected by tubes to the urogenital opening found posterior to the anus. Check around the classroom with other
groups to ensure you observe both a male and a female perch.
Respiratory and Excretory Systems - Locate and remove the bright white, gas-filled swim bladder in the dorsal
portion of the fish. On the dorsal wall of the body cavity locate the kidneys. The kidneys are connected by urinary
ducts to a urinary bladder from which wastes pass out of the body through the urogenital opening.
Circulatory System - Cut through the fish’s body wall anterior to where the liver was located. Doing this exposes a
cavity where the heart is suspended. Find the one thin-walled atrium and the one thicker-walled muscular ventricle.
You may be able to locate the one enlarged vein (sinus venosus) where blood enters the heart and the one enlarged
artery (bulbus arteriosus) where the blood leaves the heart. The blood leaving the heart goes to the gills where it
flows through capillaries in the gills and then throughout the body in various veins and capillaries and arteries and
finally returns to the heart to be pumped throughout the body again.
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Nervous System
Hold your fish in the normal swimming position. Cut the skin away from the skull and gradually scrape away the
skull bone with your scalpel. Use the picture as a guide for where to cut. When the skull becomes thin you may pick
and cut away the bone to reveal the entire brain. Be careful not to damage the brain as you cut and pick away the
skull.
In the far front towards the mouth are the olfactory lobes, followed shortly behind is the cerebrum. The two large
lobes behind that are the optic lobes, followed by the cerebellum. The Cerebellum extends posteriorly to the medulla
oblongata and, with no distinct separation, into the spinal cord.
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Questions
1. Describe the general body shape of the perch. In what way does the body show adaptations for life in the water?
2. What could be one function of the gill rakers?
3. Describe the scales of the perch. Which direction do they face? What is the advantage of this?
4. What is the gender of your perch?
5. While many invertebrates have an exoskeleton, vertebrates such as fishes have an endoskeleton. Of what
advantage is the endoskeleton to these animals?
6. The perch fertilizes its eggs externally and leaves them exposed on rocks. The guppy fertilizes its eggs internally
and gives birth to live young. Which fish produces fewer eggs? Compare the survival rate of these two species.
7. The perch possesses a gas-filled structure called a swim bladder. What is the function of the swim bladder?
8. Certain fish that live deep in the ocean have chemicals in their skin that make them luminescent. What advantage
is this characteristic to these fish?
Include a conclusion
Diagrams to label for lab prep- You must label all of the numbered parts
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