Sonatox-induced impairment of ovarian activity in an exotic cichlid, Oreochromis mossambicus

In a low dose and short chronic exposure, Sonatox (2,2,5-endo, 6-exo-8,9,10-heptachloroborane), a chlorinated insecticide, impaired ovarian activity in the fish Oreochromis mossambicus. The histological profile showed abnormalities of the different kinds of oocytes and their nuclei. Compared with the controls, a sharp drop in the proportion and diameter of the various oocytes was observed. Fish exposed to Sonatox had more atretic oocytes than were found in the controls. Percentual gonad weight in relation to body weight was also significantly reduced in treated fish (p less than 0.001). These changes are indicative of regression of the gonads after exposure to the insecticide.