Sublethal toxicological evaluation of methyl parathion on some haematological and biochemical parameters in an Indian major carp Catla catla

The sublethal toxic potential of an organophosphorus pesticide, methyl parathion (MP), in altering certain haematological (Hb, Hct, RBC, WBC, mean corpuscular volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC)) and biochemical (plasma protein and plasma glucose) parameters in an Indian major carp Catla catla was investigated under static conditions. The LC 50 (96 h) of MP was found to be 0.09 ppm. Fish were exposed to sublethal concentration of MP (0.009 ppm) for a period of 35 days, and the alterations in haematological and biochemical parameters were analysed. A significant decrease was observed in values of haematological parameters like Hb, Hct, RBC and plasma protein throughout the exposure period. However, leucocyte count was gradually increased up to the 21st day and then recovered suddenly showing a significant decrease at the end of the 35th day. MCV and MCH indices showed a significant increase during the study period, whereas MCHC value was more or less similar to control group up to the 21st day, and then a significant decrease was observed in the remaining study period. Plasma glucose values increased up to the 28th day (13.37%) and then declined. The observations presented led us to conclude that the administration of sublethal MP has significant toxic effect on fishes. These parameters could be effectively used as potential biomarkers of interest for MP toxicity to the freshwater fish in the field of environmental biomonitoring.