Toxic Impacts of Two Organophosphorus Pesticides on the Acetylcholinesterase Activity and Biochemical Composition of Freshwater Fairy Shrimp Streptocephalus Dichotomus

The 96 hrs LC50 values for malathion and glyphosate was determined to be 9.1 ppm and 5.5 ppb, respectively on the fairy shrimp, Streptocephalus dichotomus preadults. The 1/5 of 96 hrs LC50 of malathion (2.0 ppm) and glyphosate (1.1 ppb) respectively was chosen. The sub lethal toxic effect of each of these pesticides on the acetylcholinesterase activity (AchE) of S. dichotomus was assayed on days 0 and 15 of exposure, and found to be significantly decreased (0.13±0.006 nmol/mg/min) in malathion than in glyphosate when compared with control. Furthermore, the contents of selected biochemical constituents (total protein, carbohydrate and lipid) of S. dichotomus were estimated on ‘0’, 15 and 30 days of exposures, and found to be decreased significantly on 30 day in both the pesticides when compared to control. The results indicated the fact that these pesticides are toxic to S. dichotomus at the tested concentrations.