DAPHNIA MAGNA. this paper may be redistributed for educational purposes only CHRIS PANLASIGUI SEBASTIAN MORENO

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1 DAPHNIA MAGNA this paper may be redistributed for educational purposes only ; SEPT. 25, 2011 SEBASTIAN MORENO LUKE ZOTTOLI GENIE

2 this paper may be redistributed for educational purposes only Abstract This laboratory experiment was done on, a type of fresh water flea, to observe how it responds to neurotransmitters and temperature changes. The Daphnia was examined and observed to document its heart rate (HR). Then tests were conducted to determine its heart rate responses to neurotransmitters Epinephrine and Acetylcholine (ACh), low and room temperatures. A microscope and stopwatch were used to measure the changes in the Daphnia s heart rate. The results showed that the Daphnia s heart rate increased when induced with Epinephrine, and it decreased with Acetylcholine and when it was kept at a low temperature. Introduction This experiment was done to test the effects of neurotransmitters and low temperature on the heart rate of animals. The Daphnia was used to see how they respond to Epinephrine, Acetylcholine (ACh) and low temperature. As students in a Biology class, it is imperative to know the effects of environmental conditions - such as low temperature, and neurotransmitters on a different species other than human. Before the experiment, a brief group discussion was conducted to hypothesize some Daphnia responses by identifying some distinguishable effects on humans. As discussed, the following notable human heart rates effects were identified - Epinephrine causes an increase, Acetylcholine causes a decrease and so is the low (cold) temperature. This prior knowledge, allowed us to hypothesize that similar

3 this paper may be redistributed for educational purposes only effects would be seen in the Daphnia experiment it also gives us a more specific objective to continue with the experiment. Materials & Methods Materials The materials used were Acetylcholine, cotton, Daphnia, Epinephrine, microscope, paper towel, pipette, pond water, crushed ice, and a stopwatch. Methods The Daphnia was observed under a microscope with magnification power of forty times. Then the speed of its heart beat or heart rates (HR) were recorded and had assigned beats per minute or bpm as the unit. There were times when Daphnia moved a lot and sometimes violently, particularly when the Acetylcholine was applied; this made it difficult to get a precise count of the Daphnia s heartbeat to a minute length. As a solution, the group decided to restrain the Daphnia s movements by surrounding it with cotton, and then obtained a record of the heartbeat count for fifteen seconds and then multiplied the value by four to maintain a minute count. The parameter for the first test was assigned as baseline; the controlled experiment included five parameters in the following order: first, with the Pond water; second, with Acetylcholine; third, Epinephrine; fourth with low temperature; and the last was the recovery. For accuracy, we tested all parameters - baseline and controlled experiments twice then, calculated the average for each. And lastly, the group used pipette and

4 this paper may be redistributed for educational purposes only paper towel to drain the fluid and also allowed the Daphnia to rest for two minutes every after test. Observations Baseline Experiment The first baseline experiment showed that the Daphnia s heart beat one hundred forty four times (144 bmp). The second baseline test yielded the same result. So the average heart rate for both baseline testing was one hundred forty four beats per minute (144 bpm). Controlled Experiment Pond water was used in the first controlled experiment. The first HR recorded was one hundred sixty beats per minute (160 bpm) and the second HR was one hundred forty four beats per minute (144 bmp). The average HR on the pond water parameter was calculated to about one hundred fifty two beats per minute (152 bpm), a very slight increase, but an insignificant one. On the second experiment, the Daphnia s HR on the Acetylcholine was one hundred twenty beats per minute (120 bpm) and its second HR was one hundred sixteen beats per minute (116 bmp). This gave us an average of one hundred eighteen beats per minute (118 bmp). In addition to the decrease of the Daphnia s heartbeat, we also noticed an increased activity in its stomach. Though this is irrelevant with the experiment, it s worth documenting it, because it may be of use in the future. The third controlled experiment Epinephrine - showed rather a significant increase in the Daphnia s heart rate. The initial HR was two hundred forty beats

5 per minute (240 bmp) and the second HR was two hundred thirty six beats per minute (236 bmp). This gave us an average of two hundred thirty eight beats per minute (238 bpm). Cold temperature, the fourth controlled experiment, gave us an initial HR of one hundred twenty beats per minute (120 bmp) and the second HR was about one hundred sixteen beats per minute (116 bpm). The average HR for this experiment was one hundred eighteen beats per minute (118 bpm). The results reflected similarity to the results of Acetylcholine experiments. Recovery, the last parameter in the controlled experiment, gave us an initial HR of one hundred sixty beats per minute (160 bpm) and the second HR was one hundred fifty two beats per minute (152 bpm). The results showed near similarity to the baseline experiment, something that we actually would expect to obtain, as the Daphnia is to resume to its normal state. Below is a tabular and graphical representation of the observations: 1 st HR (x4) 2 nd HR (x4) Average Baseline bpm Pond Water bpm ACh bpm Epinephrine bpm Cold Temperature bpm Recovery bpm this paper may be redistributed for educational purposes only

6 300" 250" 1st"HR" 2nd"HR" Average" beats per minute! 200" 150" 100" 50" 0" Baseline! Pond Water! ACh! Epinephrine! Cold Temp! Recovery! parameters! this paper may be redistributed for educational purposes only Analysis The results of the experiment showed that neurotransmitters - particularly Epinephrine and Acetylcholine - and low temperature have chronotropic effects on Daphnia s heart rate. The experiment also validated our hypothesis would yield the similar effects to human s. As seen in the tabular and graphs, Epinephrine has a positive chronotropes or increases the heart rate, while Acetylcholine and cold temperature have negative chronotropic or decreases the heart rates.