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In this study, the effect of different levels of Lactobacillus casei in the diet was examined on the expression of growth (IGF-1 and GH), immunity (TNF-a and Lyz), antioxidants (SOD and Cat), and reproduction-related genes (FSH-R, AR, and Activin). In this study, 600 juvenile zebrafish (Danio rerio) with an average weight of 0.15‌ ± 0.01 g in 4 treatments and three replications' groups were fed with a basal diet with three levels of probiotic Lactobacillus casei (105, 106, and 107 CFU/g) for six weeks. After sex determination, the males were fed with probiotic diets for two months. Our results showed that the probiotic fed groups significantly increased the total protein, total globulin, lysozyme in the group with 107 of L. casei with respect to the control group. The L. casei fed groups showed dose dependence significant differences regarding the weight gain (%) with respect to the control group (P 0.05). Our data represented the immunostimulants effect of from L. casei was regulated by induction of immune responses in zebrafish. Furthermore, L. casei probiotic strains can improve the development profile and reproductive performance in zebrafish, which confirmes the rationale of early administration of probiotics in aquaculture.

Diazion is a common pesticide which cultured fish can be exposed. There is limited information available on the possible effects of diazinon on reproductive parameters of fish. Therefore, in this study, we focused on the effects of sub-lethal doses (0, 0.8, 1.6, and 3.2 mg/L) of diazinon, an organophosphate insecticide on sex hormones, ovarian morphology, reproductive, immunity, and antioxidant related genes, in female zebrafish (Danio rerio) after 30 days of treatment. The expression of reproductive-related genes (CYP19a, Vtg, and ERα) significantly decreased, while the expression of the immune (TNFα and Il-1β) and antioxidant (SOD and CAT) related genes increased considerably. Among sex steroids, only progesterone significantly decreased after the treatment with Diazinon sub-lethal doses, while 17-β estradiol and testosterone did not change. The ovarian morphology showed a decrease in oocyte development in diazinon-treated groups. Understanding the function and mechanism of action of diazinon on the female reproductive, immune, and oxidant status may provide new strategies to counteract its adverse effects.