aberrations in the chromosomes of cirrhinus mrigala (hamilton) upon exposure to butachlor

background: cirrhinus mrigala, one of the important fish widely consumed in india, was used for karyological observations and to evaluate the toxic effect of butachlor, an extensively used herbicide in rice fields in terms of chromosomal aberration test. methods: fishes were collected from “national fish seed farm” jyotisar with mean body weight of 20-50g. the experimental fishes were kept in two treatments each with replicate of two. there were 15 fish each in the control group (t1) without exposure to butachlor and in t2 where fishes were exposed to butachlor. results: karyotype revealed the 2n=50 chromosome from the somatic cell. chromosomal aberrations were reported after 24 hrs, 48 hrs, 72 hrs, and 96 hrs from kidney cell preparation in fishes exposed to 1.0 ppm, sublethal concentration of butachlor. frequencies of chromosomal aberration revealed a significant (p<0.05) time-dependent response. stickiness and clumping appeared at 24 and 48 hrs of exposure, end to end joining appeared after 72 hrs and chromosomal fragmentations were observed after exposure for 96 hrs. conclusion: these studies clearly revealed the genotoxic potential of butachlor even at low dose level (1.0 ppm) and suggest that butachlor interferes with cellular activities in fishes at genetic level, inducing chromosomal aberrations. therefore, the results of these investigations suggest a serious concern towards the potential danger of butachlor for aquatic organisms and the environment suggesting judicious and careful use of this pesticide in agricultural area. these aberrations in chromosome from kidney cell preparation illustrate the risk that butachlor possesses.