The Effects of Drugs on Daphnia
Investigation 4
Objective:
To learn to identify stimulants and depressants by their effect on the heart rate of Daphnia.
Materials:
Culture of Daphnia magna
Daphnia netting
Magnification chamber
Pipettes
Solutions of:
Caffeine
Epinephrine
Ethyl Alcohol
Nicotine
Unknown samples (optional)
Stopwatch or watch with a second hand
Daphnia Form and Structure Study Sheet
Procedure:
1.
Cut the Daphnia netting into small squares and place in the bottom of the magnification
chamber.
2.
Using a pipette, draw up a few Daphnia from culture dish, 1 or 2 will suffice. Place the
Daphnia in the magnification chamber, on top of the netting, with as little water as you can
transfer. This will keep them from swimming rapidly away.
3.
Practice observing the Daphnia by holding the cover of the chamber approximately 2 inches
above the top of the chamber. Locate a large Daphnia and its heartbeat. Use the diagram of
Daphnia to locate the heart.
4.
Try timing the heart rate. To do this, have your partner start the stopwatch and tell you when
to begin counting. Count for 10 seconds. Enter this heart rate in the Data Tables and
compute the heart rate per minute by multiplying by 6.
5.
Repeat this procedure 2 more time and find the average heart rate of a Daphnia. Enter this
information into the data table.
6.
Add a drop of caffeine solution to the Daphnia. Wait one minute for the solution to be
absorbed, and compute the average heart rate as performed above. Enter whether caffeine is a
stimulant or depressant.
After you have computed the caffeine affected heart rate, discard you Daphnia as per your
teacher’s instructions. Rinse out and dry your chamber and net.
7.
8.
Repeat steps 2 through 7 with each of your remaining test solutions and any unknowns that
your teacher might include.
Analysis
Data Tables
Control
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Control
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Treated with Epinephrine
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Stimulant or Depressant
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Control
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Stimulant or Depressant
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Control
Treated with Caffeine
Treated with Ethyl alcohol
Heart Rate Per
Min. (X6)
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Stimulant or Depressant
Heart Rate Per
Min. (X6)
Treated with Nicotine
Heart rate/10 sec. Trial 1
Trial 2
Trial 3
Average heart rate per minute
Stimulant or Depressant
Heart Rate Per
Min. (X6)
Questions
1.
Which substances were stimulants, which were depressants?
2.
Would it be safe to conclude that these materials would act the same way in humans?
Explain your answer.
3.
There are many substances made in the body that act as stimulants and depressants.
Propose a situation where your body might need to produce a stimulant. Propose a
situation for a natural depressant.
4.
Why was it necessary to start with a new Daphnia after each substance?
5.
Design an experiment that would test the effect of temperature on the heart rate of
Daphnia.
Further Investigations
1.
Design an experiment to test the effects of pollutants on the Daphnia heart rate.
Investigate materials such as pH, trying to simulate the pH found in an acid polluted lake.
2.
Go out with a small aquarium net to a pond and run it through some weeds along the side.
Put the creatures that you catch into a jar. There should be some Daphnia there. Bring
these Daphnia back to the lab and investigate their heart rates. Compare the durability of
a wild Daphnia to a lab raised Daphnia.