Investigation of sex maturity and morphohistology of gonad in the broodstock of (Hamilton, 1822) Danio rerio influenced by probiotic (Lactobacillus plantarum)

In order to increase the knowledge of the probiotic effects on reproductive indices of fish, this study was conducted to investigate the effects of different levels of probiotic Lactobacillus plantarum on gonadal development and sexual maturation in zebrafish (Danio rerio). Some 720 zebrafish were fed the experimental diets in four treatments such as: 0%, 0.5%, 1.5% and 3% probiotic diets for 40 days. Based on the measurement of reproductive indices in this species, the maximum absolute fecundity was observed in the diet containing 3% probiotic, which was significantly different from the control treatment and the diet containing 0.5% probiotic. Based on relative fecundity index, the control treatment showed the lowest fecundity rate compared to the other treatments. The gonadosomatic index data showed the utmost gonadal index in the diet containing 3% probiotic compared to the other treatments, which was significantly higher than the control and 0.5% probiotic treated diets, but it did not show any significant difference with the diet fed 1.5% probiotic. Histological examination of gonads in males and females showed gonads development and complete sexual maturity in treatments fed 3% and 1.5% probiotic levels. The present study indicates that probiotic Lactobacillus plantarum at 3% level will have the best effect on reproductive and gonadal development parameters in zebrafish.