殺蟲劑(Malathion, Cypermethrin, Paraquat)對圓水蚤(Daphnia pulex)之急毒性及趨光行爲之探討

Abstract

Purpose: This study investigates the influences of three commonly used pesticides on the phototactic swimming behavior of the water flea, Daphnia pulex, an index of acute toxicity. Methods: In this study we measured the effect of three representative pesticides on laboratory cultivated fifth generation water fleas in a medium of hard water similar to that found in nature. We carried out a series of experiments using variety of densities and measured acute toxicity in Daphnia pulex neonates, observed water flea swimming behavior by image recording, and analyzed swimming path Results: The 24h-EC50 values detected by Daphnia pulex showed that the Malathion had the highest nerve toxicity of 0.l2ng/L, followed by Cypermethrin (5.4mgIL) and Paraquat (12.5mg/L). The 48h-EC50 values detected by Daphnia pulex showed that Malathion had the highest toxicity (0.05ngIL), followed by Cypermethrin (2, 3mg/L) and Paraquat (7.3mgIL). Analysis of water flea swimming behavior showed that, at the 10(superscript th) minute of the pesticide Paraquat test, the water flea swimming speed in the group with a density of 25 ppm was significantly different (P＜0.001) from those in the other groups. At the 10(superscript th) minute of the pesticide Malathion test, swimming speed in the group with a density of 1 ng/L was significantly different (P＜0.001) from those of the other groups. At the 10th minute of the pesticide Cypermethrin test, swimming speed in the group with a density of 2.5 mg/L was significantly different (P＜0.001) from the other groups. Conclusion: The methods used herein can be applied to detect the 24h-EC50 value of water flea at the particular density and exposure time. The sensitivity of swimming behavior was highest between the 5(superscript th) and the 15(superscript th) minute, The results of this study can be used as a reference when assessing reaction time in the swimming of water fleas exposed to various pollutants.