Cardiovascular Performance Measurement in Water Fleas by Utilizing High-Speed Videography and ImageJ Software and Its Application for Pesticide Toxicity Assessment

Abstract

Water fleas are a good model for ecotoxicity studies, and were proposed for this purpose by the United States Environmental Protection Agency, due to their easy culture, body transparency, and high sensitivity to chemical pollution. Cardiovascular function parameters are usually used as an indicator of toxicity evaluation. However, due to the nature of the heart and blood flow, and the speed of the heartbeat, it is difficult to perform precise heartbeat and blood flow measurements with a low level of bias. In addition, the other cardiovascular parameters, including stroke volume, cardiac output, fractional shortening, and ejection fraction, have seldom been carefully addressed in previous studies. In this paper, high-speed videography and ImageJ-based methods were adopted to analyze cardiovascular function in water fleas. The heartbeat and blood flow for three water flea species, Daphnia magna, Daphnia silimis, and Moina sp., were captured by high-speed videography and analyzed using open-source ImageJ software. We found the heartbeat is species-dependent but not size-dependent in water fleas. Among the three water fleas tested, D. magna was identified as having the most robust heartbeat and blood flow rate, and is therefore suitable for the ecotoxicity test. Moreover, by calculating the diameter of the heart, we succeeded in measuring other cardiovascular parameters. D. magna were challenged with temperature changes and a pesticide (imidacloprid) to analyze variations in its cardiovascular function. We found that the heartbeat of D. magna was temperature-dependent, since the heartbeat was increasing with temperature. A similar result was shown in the cardiac output parameter. We also observed that the heartbeat, cardiac output, and heartbeat regularity are significantly reduced when exposed to imidacloprid at a low dose of 1 ppb (parts per billion). The blood flow rate, stroke volume, ejection fraction, and fractional shortening, on the contrary, did not display significant changes. In conclusion, in this study, we report a simple, highly accurate, and cost-effective method to perform physiological and toxicological assessments in water fleas.

Exploiting the Freshwater Shrimp Neocaridina denticulata as Aquatic Invertebrate Model to Evaluate Nontargeted Pesticide Induced Toxicity by Investigating Physiologic and Biochemical Parameters

“…IMI exposure is known to cause a depressed heart rate. Previous experiments demonstrated that IMI exposure to D. magna could affect heartbeat by reducing the heart rate of D. magna in all of the tested concentrations [67]. In another D. magna study, a similar result was noted when D. magna was exposed to neonicotinoid insecticides.…”

“…A previous study has also proven that temperature can also affect the heartbeat. In Daphnia , heart rates display a good positive relationship with ambient water temperature [ 67 ]. In M. edulis , a high temperature was observed to increase the heartbeat.…”

An OpenCV-Based Approach for Automated Cardiac Rhythm Measurement in Zebrafish from Video Datasets

“…The success of detecting cardiac rhythm in zebrafish by the OpenCV method promotes us to test whether our approach is also functional when applied to ultrafast heartbeat events in water fleas. We analyzed heartbeat data for Daphnia magna reported by Santoso et al [72]. The control peaks for Daphnia magna heartbeat analyzed by OpenCV method can be found in Figure S1, with a good signal-to-noise ratio.…”

“…In previous studies, our team has developed several simple and cost-effective ImageJbased methods to conduct cardiac rhythm detection in zebrafish and Daphnia [21,26,72]. In order to effectively reduce the relative complexity for manual or semi-automated operation, in this study, we aimed to develop an automated tool for cardiac rhythm detection in zebrafish by using OpenCV.…”

Measurement of Multiple Cardiac Performance Endpoints in Daphnia and Zebrafish by Kymograph

“…Within these factors, the environmental factor, especially temperature, is capable of inducing fast bradycardia or tachycardia [50]. Due to being ectothermic organism, changes in water temperature can significantly alter D. magna heart rate [51]. An increase in temperature will increase metabolic activity resulting in high cellular oxygen demand, which increases heart activity to fulfill the demand, while the opposite happens during low temperatures [52].…”