Chemical control: observing the excitatory effects of MSG compared to the inhibitory effects of KCl in the heart rate of Daphnia magna

Abstract

From tiny Daphnia magna to humans and other mammals, heart rate is a quantitative characteristic for several species. In this study, we measured the effect of two different chemicals on the heart rate of Daphnia by comparing the heart rate of the Daphnia before and after the addition of each chemical. Our experimental design was unique to our goal by comparing the effects of a KCl solution and an MSG solution to Daphnia in a normal environment without either chemical to see the average percent change in heart rate that was caused by the chemical. Daphnia heart rate was measured under a light microscope and recorded with an iPhone in slow motion to accurately determine the number of beats per minute. Once averaged, the results indicated that there was a 16.76% increase in heart rate due to the addition of MSG and a 34.51% decrease when put in a KCl solution. Our results may be beneficial to those wishing to study the effects of other excitatory or inhibitory chemicals on subjects such as humans, as a strong correlation has been made between the change in heart rate for both humans and Daphnia.