Abstract
Nigella sativa has been used in aquaculture as growth promoter and sex reversal agents, but its toxicity has not been investigated. This study tries to investigate the histopathological effects of Nigella sativa (Black cumin) seed extract on gonads of Coptodon zillii (Red belly). The extract was prepared using standard procedures. Coptodon zillii; Extract; Gonads; Histopathology; Nigella sativa, Ovaries and TestisCoptodon zillii; Extract; Gonads; Histopathology; Nigella sativa, Ovaries and TestisCoptodon zillii; Extract; Gonads; Histopathology; Nigella sativa, Ovaries and TestisCoptodon zillii; Extract; Gonads; Histopathology; Nigella sativa, Ovaries and TestisCoptodon zillii fry were obtained and randomly assigned into four different treatment groups (0.0g/l, 0.05g/l, 0.1 g/l and 0.15g/l) in triplicate. The experiment was conducted within a period of 8 weeks in which the Coptodon zillii were immersed in extract once per week. The gonads of the Coptodon zillii were then analyzed histologically. The ovary and testis of fish in the control group (0.0g/l) showed normal ovarian tissues and normal distribution of the testicular tissues. However, dose-dependent degeneration of the testicular tissues and semineferous tubules as well as an uneven distribution of spermatozoa were observed in the gonads of the test groups. The ovaries also show dose-dependent atrophy of the primary oocytes as well as degeneration of connective tissues and primary oocytes. The histopathological examination revealed mild ovarian and testicular histopathological damage. The results obtained suggest that the plant is toxic to the gonads of C. zilli at the evaluated concentrations. It is advisable to use lower concentrations of the extracts.

Key words: Coptodon zillii; Extract; Gonads; Histopathology; Nigella sativa, Ovaries and Testis