The effect the various drugs caffeine, nicotine and epinephrine had on the Daphnia magna is displayed in Figure 1. After three sample trials were taken there was an average of 180 beats/min-1 ± 6.928 taken under normal conditions. The addition of caffeine caused an increase in the average heartbeat to change to 192 beats/min-1 ± 9.165 in the Daphnia magna tested. When testing the effect of nicotine on the Daphnia magna the average heart beat was 168 beats/min-1 ± 3.4641 taken under normal conditions. With the addition of nicotine, this caused a decrease in the Daphnia’s heart beat with an average of 146 beats/min-1 ± 8.717798. When the heart beat was taken under normal condition for the testing of epinephrine, the average heart beat was 192 beats/min-1 ± 3.4641. There was an increase in heartbeat of an average of 206 beats/ min -1 ± 7.211103 when the Daphnia magna was put in a solution of the drug, epinephrine.
When testing for the effect ethanol has on the Daphnia magna’s heart, the average heartbeat taken under normal conditions was 162 beats/min-1 ± 9.165. With the addition of the Daphnia magna in a solution of ethanol, there was a decrease in the heartbeat changing it to 140 beats/min-1 ± 7.2111. The results testing for the effect different salt concentrations have on the Daphnia magna’s heartbeat is shown in Figure 2. When obtaining the control for the different concentrations, of the [0.05], [0.04],[0.03],[0.02] and [0.01] the average heart rate for the five different samples consisting of three trials each were, 164 beats/min-1 ± 8.717798, 170 beats/min-1 ± 2, 160 beats/min-1 ± 11.13553, 162 beats/min-1 ± 6.928203 and 166 beats/min-1 ± 8.717798 respectively. When testing effects the different concentrations had on the Daphnia’s heart rate there was fluctuation in the data obtained.
When the different Daphnia magna were put into the different concentrations of 0.05 g/µliter, 0.03 g/µL, and the 0.01 g/µL salt solutions, the average heart rate increased with 198 beats/min-1 ± 9.165151with a percent change of 20.73%, 194 beats/min-1 ± 5.291503 with a percent change of 16.87%, and 196 beats/min-1 ± 4 with a percent change of 18.07% respectively. When the different Daphnia magna were put into the different concentration of 0.04 g/µL and 0.02 g/µL salt solutions, the average heart rate decreased with 168 beat/min-1 ± 10.3923 with a percent change of -1.18% and 150 beats/min-1 ± 3.464102 with a percent change of -7.41% respectively. Discussion
Daphnia magna have been used mainly to test two things, whether or not Daphnias can be used as model for to understand the effects different toxins have on humans and as indicators for environment pollution issues present. When looking at the effects caffeine and epinephrine had on the heart rate of the Daphnia magna, it showed that they are stimulants by the increase in the Daphnia’s heart rate in comparison to the heart rate of the control group. This reflects accurate results reproduced by another experiment performed by Campbell et al (2004). When looking at the effects nicotine and ethanol had on the heart rate of the Daphnia magna, it showed that they were depressants by the decrease in the Daphnia’s heart rate in comparison to the heart rate of the control group.
The results of Ceballos et.al (2010) supported the results obtained in this experimental. Ceballos et.al (2010) experiment analyzed further and noticed that the nicotine had different effects on the Daphnia’s heart rate based on two factors, the amount of time that was given for the Daphnia to absorb the nicotine and the concentration of nicotine given to the Daphnia. For the testing of the salt concentration, it was hypothesized before the experiment began that as the salt concentration decreases, the heart rate would decrease as well. The results did not support this hypothesis. It has been established that heart rate in Daphnia magna increases when there is a progressive lack of oxygen present. (Baumer et.al 2002).
When the salinity of water increases there are increases in Na+ ions as well as Cl- ions. This increase in ion concentration causes a change in osmotic alternation and a competition between all the ions. (de la Paz Gomez-Diaz and Martinez-Jeronimo 2008). Although increase in salinity has been known to be detrimental to the health of the Daphnia magna, if high enough can result in mortality, Daphnia magna can adapt to low levels of salt (Baillieul et.al 1996). Since the Daphnia magna are freshwater crustaceans the lower the salt concentration there is the closer the heart rate should be to the resting heart rate of the Daphnia. Possible errors that could have gone wrong are the duration given to allow for the absorption of the different concentration of salt solutions due to the limited time during the lab period and the distinguishing of the separate heart beats and the inaccuracy of a constant time being off by points of a second.
