Acute Toxicity and Cytogenetic Effects of Monocrotophos in Paramecium Caudatum and Oxytricha Fallax

In the present study experiments were conducted to evaluate the toxic effects of monocrotophos on ciliate models Paramecium caudatum and Oxytricha fallax, which can be considered as ideal organisms for investigating water quality fluctuations and risk assessment of pesticides. Cell viability, cell morphology, cell behaviour and macronucleus tests were performed using to different concentrations of monocrotophos. The calculated LC50 value of monocrotophos against mortality curve for 3hrs exposure to Paramecium caudatum and Oxytricha fallax was 332.284±57.52ppm and 307.744±33.27ppm respectively. It was observed that the Oxytricha fallax was sensitive and Paramecium caudatum was highly responsive to monocrotophos. After a short period of exposure (20min to 30 min), there was an increase in the number of necrotic cells with typical features like blackening of cytoplasm, blebbing, leaking of internal contents and macronuclear changes leading to cell lysis. Changes in the contractile vacuole activity, size and shape of the organisms and macronucleus shape were also noticed. The present findings indicate a possible necrotic and ecogenotoxic effect of monocrotophos to Paramecium caudatum and Oxytricha fallax and such type of assays suggest the potential of above organism for ecotoxicological studies to certain pesticides.