Daphnia magma: the effect of alcohol and caffeine concentrations

Introduction 

Alcohol and caffeine are among the most popular beverages ( Kundu, & Singh, 2018) . While the two drinks have been implicated to being highly addictive, their health effects transcend addiction. Alcohol is a central nervous system (CNS) depressant that causes a euphoric sensation and mild hyperactivity at the onset of intoxication. However, at higher concentrations, the anesthetic effects of alcohol take effect, and the CNS activity is inhibited (Parandela et al., 2016). The CNS controls the functioning of other body systems. Its inhibition, therefore, has a resultant effect of reduction in cardiovascular activities and heart rate. Caffeine, on the other hand, is a CNS stimulant that causes an increase in the activity of the CNS as well as constriction of the blood vessels. This has a synergistic effect of increasing the heart rate. Studies have shown that the heart rate increases proportionally with an increase in the concentration of caffeine ( Voskoboinik, Kalman, & Kistler, 2018; Parandela et al. , 2016). However, extremely high concentrations of caffeine may cause heart failure. 

Daphnia magna , commonly known as a water flea, is a transparent freshwater crustacean with genome homologous to the human genome. The transparent body of the animal makes it easy to observe the effects of alcohol and caffeine on its heart rate under a microscope, without invasive interventions. The thin membrane that protects the animal’s internal organs is easily permeable to different substances, allowing real-time observation of the effects of substances on the animal’s heart rate. Daphnia can easily be cultured and has a short lifespan. These characteristics make the animal ideal for studying the effects of CNS stimulants and depressants on the heart rate of an animal. 

Image 1: Anatomic features of Daphnia magma. 

Hypothesis: 

Alcohol has a concentration-dependent decrease in the heart rate of Daphnia magma . Higher concentrations of exposure to alcohol further decrease the heart rate. 

Caffeine has a concentration-dependent increase on the heart rate of Daphnia magna . Increase in concentrations which the organism is subjected to will result in further increase in the heart rate. 

Independent Variable: 

The concentrations of alcohol and caffeine which the animals are exposed to are the independent variables of the experiment. 

Dependent Variable: 

The heart rate to be dependent is the dependent variable. 

Constant Variable 

-Time: The timing was kept the same observation of the heart rate for all the animals in different alcohol and caffeine concentrations. 

-Temperature: The experiment was conducted under controlled temperature. 

Control Group 

The control group was animals that were exposed to water from their tank and their heart rate observed. 

Procedure 

A live Daphnia was obtained from the culture jar, and placed in a depression slide, along with a drop of water from the culture. 

The anatomy of the organism was observed to make sure that the heart was beating. Observe the anatomy of the organism, and make sure you can see the heart beating. The anatomical structures to the diagram in this handout were compared 

The number of heartbeats was counted for 15 seconds. The normal rate for a healthy organism is 2-5 beats per minute. The number of heartbeats in 15 seconds was multiplied by 4 to get the number of heartbeats/minute. 

One drop of the 0.5% caffeine solution was placed on daphnia in the depression slide. After one minute the number of heartbeats was counted for 15 seconds. The data was recorded on the data table. The animal was removed and returned to the culture dish for used animals. 

The procedure 1 -4 was repeated for nine other animals. 

Data 

	Solution:
Daphnia number	Heartbeats in 15 seconds	Heartbeats/minute
1	9	35
2	17	66
3	20	81
4	24	96
5	21	83
6	22	89
7	22	86
8	24	95
9	22	89
10	22	88
AVERAGE	20	81

Table 1: Heart rate of Daphnia magma placed in 0.5% caffeine solution in. 

Table 1 above shows the experimental data of the heart rate per fifteen seconds and minute of 10 daphnias placed exposed to 0.5% caffeine solution. The heart rate was determined by counting the movement of the antenna on the organisms’ bodies rather than observing the heart. The average heartbeats per fifteen seconds and one minute were obtained by dividing the sum of the heartbeats by the number of animals included in the experiment (10). According to the data obtained, the average heart beats for Daphnia magma exposed to 0.5% caffeine solution is 81 beats per minute (20 beats/15 seconds). 

Class Data 

Treatment Group	Heartbeats per minute
Control	41
Caffeine low dose – 0.5%	81
Caffeine high dose – 2.0%	82
Alcohol low dose – 2%	41
Alcohol mid dose – 5%	43
Alcohol high dose – 8%	33

Table 2: Class data showing the average heart beats per minute of daphnia magma exposed to varying alcohol and caffeine concentrations. 

The data in table 2 above is the average class data of the heart rate per minute of daphnia when exposed to 0.5%, 2.0% caffeine solutions and 2%, 5%, and 8% alcohol solutions, and that of the control group. According to the data, the average normal heart rate of daphnia (control group) is 41 heartbeats per minute. The average heart rate increase on exposure to 0.5% caffeine (81 beats per minute) and is even higher when the concentration of caffeine is increased to 2% (82 beats/minute). The data shows that alcohol has a negative effect on that of caffeine. The average heart rate is normal (41 beats per minute) at 2% alcohol concentration. The heart rate, however, increases at mid-dose alcohol concentration (43 beats per minute) but drastically decreases at high alcohol concentration (33 beats per minute). 

Conclusion 

The results obtained from the experiment show that caffeine increases the heart rate. Increase in the concentration of caffeine further increases the animal’s heart rate. According to Voskoboinik, Kalman, & Kistler, (2018) the CNS stimulating activity of caffeine is through the release of plasma catecholamines and the inhibition of adenosine receptors (A1 and A2). These physiological mechanisms have a consequent effect of augmenting cardiovascular activities, resulting in increased blood pressure and tachycardia. The results from the experiment support the experiment’s hypothesis. However, the results do not fully support the experiment’s hypothesis as the higher concentration of caffeine (2% solution) is less ineffective than the lower concentration (0.5% solution). This considerable difference in effectiveness might have been as a result of experimental error. Alcohol has contradicting effects on the heart rate of the organism. The heart rate increases then drastically decrease when the animal is exposed to high alcohol concentrations. This decrease in the heart rate at high alcohol concentration supports the experiment’s hypothesis. According to a study by Immanuel et al., (2016), alcohol causes a euphoric effect at the beginning of exposure. The euphoria is perceived as hyperactivity, which might exhibit pseudo-stimulatory effects on the CNS. This explains the increase in the animal's heart rate on exposure to mid alcohol concentration. At higher concentrations, the stimulating effects wane and the CNS-inhibition effects set in. Inhibition of the CNS slows down physiologic functions such as respiration and cardiovascular activities. Blood pressure and the heart rate decrease drastically. Studies by Gonzaga et al., (2017) and Kundu & Singh (2018) found that caffeine and alcohol increase and decrease the heart rate respectively. The results of this experiment can be used to explain cardiovascular occurrences in humans following the consumption of alcohol and caffeine. 

Performing the experiment using ten animals was important to enhance the accuracy of the results obtained. This, however, might have a source of error because the animals have different physiological characteristics such as age, size, and sex. These characteristics affect physiological functions such as heart rate. Other sources of error might have been conducting the experiment outside Daphnia’s ecological niche. The change in environment and handling the animal while moving it to the observation slide could affect the blood pressure of the organisms. The duration of exposure before taking the heart rate count was short. The heart rate might have been different if the count had been taken a minute or two after exposure. Furthermore, the determination of the heart rate was done by manually observing and counting the movement of antennae on the animal’s body. Blinking or sneezing could cause one to miss counting some movements, resulting in erroneous results. 

References 

Gonzaga, L. A., Vanderlei, L., Gomes, R. L., & Valenti, V. E. (2017). Caffeine affects autonomic control of heart rate and blood pressure recovery after aerobic exercise in young adults: a crossover study.  Scientific reports ,  7 (1), 14091. doi:10.1038/s41598-017-14540-4 

Kundu, A., & Singh, G. (2018). Dopamine synergizes with caffeine to increase the heart rate of  Daphnia .  F1000Research ,  7 , 254. doi:10.12688/f1000research.12180.1 

Paradela, I. P., Celdran, P. B. M. I., Canalita, E. E., & Tarranza, V. A. (2016). Study on the Effect of Alcoholic Beverages on the Heart Rate of Daphnia (Daphnia magna). 

Voskoboinik, A., Kalman, J. M., & Kistler, P. M. (2018). Caffeine and Arrhythmias.