Pre-lab: Trout Dissection

Trout Dissection
☆ Trout Diagram (18) (-10 if not complete on dissection day)
(Results, Sketches/diagrams)
Using the diagrams provided by the instructor to make a biological drawing of a trout.
Use pencil, unlined paper, at least a half page, place the title underlined below the
Color completed drawing with colored pencils.
Use a ruler to draw label lines. Do not write on label lines.
Include the following labels: (12) gills, heart, liver, intestinal caecum, stomach, caudal
fin, pectoral fins, pelvic fins, anal fin, swim/gas bladder, kidney, spleen.
Place drawing in the section of your write-up.
External anatomy
1. Describe the appearance of the trout: size and coloring. Be specific. (Observations)
2. On the trout, locate and review all external structures labeled in your drawing.
3. Answer questions 1- 6 in the questions part of the write-up. (Questions)
Internal Anatomy
4. Cut away one of the bony flaps over the gills. Describe the gills. (Observations)
5. Using scissors, cut through the body wall along a line from the anus to just behind the
gills, just inferior to the centerline (dorsal side) of the fish. Be careful to hold the tips of
the scissors up to avoid damage to the under-lying tissue.
6. Lay the fish on its side and continue the cut around the back of the gills upward to the
dorsal surface.
7. Go back to the cut that began at the anus and cut upward from the anus. This
completes your “window flap”.
8. Carefully pull back the muscle tissue to expose the viscera.
9. Answer question 7 in the questions part of the write-up. (Questions)
10. Cut across the fish from the anterior part of the window flap to its posterior border to
remove the “window flap”.
11. Dispose of the removed flap in the appropriate container.
12. Identify all internal organs labeled in your drawing.
13. Answer question 8 in the questions part of the write-up. (Questions)
14. Probe to find the liver and the spleen. Answer question 9. (Questions)
15. Cut into the stomach. Answer question 10. (Questions)
16. Make an anterior cut to the liver under the gills. Answer question 11. (Questions)
17. Make an incision down the midline of the dorsal side of the fish to expose the brain.
18. Answer questions 12 & 13. (Questions)
19. Label all the structures on the provided trout drawing. (Sketches/Diagrams)
20. Dispose of the trout in the appropriate container.
21. Clean and dry all equipment and return to its proper place.
22. Clean and dry your work area.
Questions (30)
(3) What does the fish feel like? Name two reasons why it feels this way.
(2) What is the faint line running down the sides of the trout? What is its function?
(2) Does the fish have teeth? If so, what do they feel like?
(2) Name the fins that are paired.
(3) The fish dissected is either a Rainbow or a Rainbow/ Snake River Cut-throat trout.
Describe each type. Which do you think you are dissecting? Why?
6. (3) What are bony flaps covering the gills called? What are their two functions?
7. (2) Identify the long, shiny, clear sac near the middle of the fish. What is its function?
8. (5) List all the internal organs that you can identify.
9. (2) What color are the liver and the spleen? Why?
10. (1) What is inside the stomach?
11. (1) What organ located under the liver?
12. (2) How does this brain compare to the shark’s brain? (Color, size, texture, lobes)
13. (2) Is the trout a lobe-fined or ray-finned fish? To which Class does it belong?
This is a formal lab write-up.
Use the on-line template.
Include all parts and headings, except for the following.
Delete the following:
 Under purpose: Hypothesis
 Method
 Under conclusions:
Sources of error