Equipment
Method
Variables-'Control the controllables'
- Microscope
- Petri Dish
- Small Piece of cotton wool
- Pasteur pipette (for water from the Daphnia culture tank)
- Caffeine of different concentrations
- Culture of Daphnia
- Counter
Method
- Take a small piece of cotton wool and place it in the middle of a small petri dish
- Select a Daphnia, then use a Pasteur pipette to transfer the organism to the cotton wool
- Add pond water to the petri dish until the animal is covered by the water
- Place petri dish under the microscope and identify the position of the heart
- Record the heartbeat of the Daphnia over 20 seconds. Multiply result by 3.
- Take the Daphnia off of the microscope to avoid heating it up, place the Daphnia into another petri dish but this time using different concentrations of caffeine solution; 0.001, 0.01, 0.1, 1, 10, 100 %
- After allowing the Daphnia time to acclimatise to the new solution place under the microscope and record the heart beat
- Repeat for different concentrations of caffeine
Variables-'Control the controllables'
- Temperature- an increased temperature will result in an increased heart rate, therefore it is important that the temperature is controlled within this experiment.
- Stress- it is important to not stress the Daphnia in any way as this will increase the heart rate, the Daphnia should be handled with the utmost respect and not pressured in any way to achieve results that you want it to.
- Rest period- between each experiment the Daphnia should have a rest time to recuperate and for the heart rate to return to a resting level, if the Daphnia has an increased this will affect the value for the change in heart rate.
Results
The results we produced show that heart rate increased with caffeine concentration, as the caffeine concentration increased the average increase in heart rate increased to a peak and then reduced again. Our results show that in a 0% concentration of water the heart rate increased by 40 bpm on average, this is unexpected as you would expect no change in heart rate. This suggests that we did in fact stress the Daphnia through the transfer of it onto the slide. Therefore most of our results are invalid and therefore any conclusion that you make is invalid. Daphnia are widely used to test the toxicity of products recently shown by a 2015 paper(1.). This is often where new drugs are tested on first to see whether they are too toxic to make it through to the next round of trials. This is acheived through a Proteomic analysis, here electrophoresis is used to see whether the protein expression within a Daphnia is used.
1.Proteomic analysis of Daphnia magna exposed to caffeine, ibuprofen, aspirin and tetracycline
AuthorsSeung Hyuck BangNam-Hui HongJi-Young AhnSimranjeet Singh SekhYang-Hoon KimJiho Min
The results we produced show that heart rate increased with caffeine concentration, as the caffeine concentration increased the average increase in heart rate increased to a peak and then reduced again. Our results show that in a 0% concentration of water the heart rate increased by 40 bpm on average, this is unexpected as you would expect no change in heart rate. This suggests that we did in fact stress the Daphnia through the transfer of it onto the slide. Therefore most of our results are invalid and therefore any conclusion that you make is invalid. Daphnia are widely used to test the toxicity of products recently shown by a 2015 paper(1.). This is often where new drugs are tested on first to see whether they are too toxic to make it through to the next round of trials. This is acheived through a Proteomic analysis, here electrophoresis is used to see whether the protein expression within a Daphnia is used.
1.Proteomic analysis of Daphnia magna exposed to caffeine, ibuprofen, aspirin and tetracycline
AuthorsSeung Hyuck BangNam-Hui HongJi-Young AhnSimranjeet Singh SekhYang-Hoon KimJiho Min