Cytogenotoxicity assessment of monocrotophos and butachlor at single and combined chronic exposures in the fish Catla catla (Hamilton)

Cytogenotoxic effects in the form of micronuclei and deformed nucleus, nuclear buds, binucleated cells, vacuolated nucleus, vacuolated cytoplasm, echinocytes, and enucleus induced by two compounds belonging to two different chemical classes of agrochemicals (monocrotophos and butachlor) at sublethal concentrations (0.625, 1.3, and 2.3 ppm and 0.016, 0.032, and 0.064 ppm) in single and combined chronic exposures were studied under laboratory conditions for a period of 35 days in the economically important Indian fish Catla catla . Statistically significant duration-dependent increases in the frequencies of micronucleus (MN) and other cytological anomalies were observed. Compared to single exposures, a twofold increase in micronuclei frequency was noted at combined exposures indicating the synergistic phenomenon. Binucleated and enucleated cells appeared only in fishes exposed to sublethal concentrations of butachlor. The present study is the first of its kind in exploring a significant positive correlation between micronuclei and other nuclear anomalies suggesting them as new possible biomarkers of genotoxicity after agrochemical exposures. The study highlights the sensitivity of the assay in exploring various predictive biomarkers of genotoxic and cytotoxic events and also elicits the synergistic effects of agrochemicals in apparently healthy fishes. C. catla can be considered as a suitable aquatic biomonitoring sentinel species of contaminated water bodies.