Name ___________________________ Partners _________________________ Date _____________
Investigation: Fish Circulation
The movement of blood cells through blood vessels is hard to observe in humans, but can be seen clearly
in the tail of a goldfish. In this investigation you will observe the normal flow of blood through the
capillaries of a fish’s tail and hypothesize how alcohol and nicotine would effect the rate of blood flow
through them.
Materials:
Lab aprons, gloves, 250 mL beaker, dropping pipets, petri dish, absorbent cotton, paper towels, lens
paper, dip net, compound microscope, beaker of spring water, one goldfish
Procedure:
1. Put on lab aprons and gloves. Read through the entire procedure before starting. Cut a thick piece of
cotton slightly larger than needed to wrap around the goldfish. Soak the cotton in spring water and
place the wet cotton in the petri dish.
2. Using the dip net, catch a goldfish and gently place it so the gills are covered with the wet cotton but
not its tail and head. See Figure 1.
3. Wet the head and tail of your fish every few minutes with a pipet.
Do not allow your goldfish to dry out. If the circulation stops, remove the fish from the cotton. Apply
artificial respiration by rapidly pushing the fish through the water in the tank once or twice. Then
wrap it up again in the wt cotton. In handling the fish use the wet cotton or a net and do not touch the
skin with your fingers.
4. Place the petri dish with the wrapped fish on the
microscope stage. Focus the low power on the tail and
move the dish around until you locate a part of the tail in
which you can observe blood vessels clearly. The red bodies
you see are the masses of pigment. Near the posterior edge
of the tail the pigment thins out and you can see the blood
vigorously flowing through vessels. Concentrate your
observations in this region.
Figure 1. Preparation for observing fish circulation
5. Identify the small arteries and veins. How can you recognize them?
6. Find and examine some capillaries. Sketch a portion of the tail you are observing.
veins, and capillaries and their cross section dimensions.
label the arteries,
7. Compare the walls of the three types of blood vessels. Record your observations.
8. Compare the rate and method of blood flow in the three types of blood vessels. Record your
observations.
9. For a period of three or four minutes carefully observe the blood cells in a group of capillaries.
Compare the diameters of the capillaries and the red blood cells. Does each capillary function
continuously? Explain. Does blood always flow in the same direction through a particular capillary, or
does the flow change direction?
10. When you have finished with the fish, replace it in the fish tank. If it does not revive immediately,
apply artificial respiration. Wash your hands before leaving the laboratory.
Fill in the summary table of a comparison of your observations of the blood vessels.
Type of vessel
Structure of Wall
Rate and method of blood flow
Analysis: Type your answers to the questions with enough information so the meaning of the
question is clear. Attach them to your lab. Site your sources of information with dates and
publishers
1. What is the function of each type of blood vessel? How is each type of vessel’s structure adapted
perform this function?
2. Describe how blood flows through a capillary and how this compares to the speed of blood flow in
arteries and veins? Explain the reasons for these differences.
3. How could you tell an artery from a vein?
4. What is the effect of alcohol on the diameter of blood vessels. (Look this up)
5. What is the effect of nicotine on the diameter of blood vessels. (look this up).
6. If the effect of nicotine on humans is the same as its effect on fish, how might nicotine affect the
performance of athletes?
7. If the effect of alcohol on humans is the same as its effect on fish, how would alcohol consumption
affect persons exposed to cold weather?
8. The alcohol and nicotine effects we are considering were produced under laboratory conditions and are
not natural effects. Under what natural conditions might capillary diameter change?