TOXIC EFFECTS (BY LC 50ANALYSIS) OF CYPERMETHRIN ON A CYCLOPOID COPEPOD , MESOCYCLOPS LEUCKARTI (CLAUS, 1857)

Use of pesticides has been a very common practice in modern agricultural methods and out of them insecticides are potentially the most toxic to aquatic invertebrates, especially, when they get drained off into the natural water bodies, thus posing a threat to the aquatic organisms. The present study was carried to elaborate the lethal effects of one s uch pesticide (cypermethrin) on the fresh water cyclopoid copepod , Mesocyclops leuckarti (Claus, 1857). Cypermethrin is known to be a highly efficient pesticide. The LC 50 studies conducted on the copepod have indicated that even minute doses like 0.0001 pp m were lethal, for M. leuckarti when exposure time was 96 hours. The forthcoming paper details LC 50 values of this pesticide for different periods of exposure. The 2, 24, 48, 72 and 96 h LC 50 values of cypermethrin for adult Mesocyclops leuckartiwere estimated at 0.00085 ppm, 0.00063 ppm, 0.00038 ppm, 0.00032 ppm and 0.00029 ppm, respectively. Obtained data from the cypermethrin acute toxicity tests were evaluated using the probit analysis method.