Mealworm extract (Tenebrio molitor) affects gonad histology, reproduction performance and related genes expression in female zebra fish (Danio rerio)

Abstract This study investigated the effects of dietary supplementation with the methanolic extract of yellow mealworm ( Tenebrio molitor ) (MME) on reproductive indices, reproduction- and long-chain PUFA biosynthesis related gene expression and gonadal histology in female zebrafish ( Danio rerio ). Zebrafish were fed four dietary regimes, 0% (MME0), 0.25% (MME1), 0.5% (MME2) and 1% (MME3). Oocyte diameter, PVS diameter, gonad weight, number of eggs, absolute and relative fecundity increased in the MME3 group, while GSI increased in both the MME2 and MME3 groups ( ). MME supplementation led to dose-dependent increases in 17-OH-Progesterone (17-OHP) and 17-β-Estradiol (E2) hormone levels. All 3 MME groups showed significant differences with control group ( ). The inclusion of MME in the zebrafish diet led to a significant increase in long-chain PUFA and reproduction-related gene expression compared to the control group ( ). The highest increase in Elovl2 expression was observed in the MME3 group, while MME2 and MME3 showed the greatest increases in Elovl 5 expression ( ). For reproduction-related genes, the expression levels of VTG, CYP and ERα displayed a dose-dependent increase, with the most significant rise in the MME3 group ( ). Histological analysis of gonads revealed that most oocytes were at beginning of Stage III in MME0, at end of Stage III in MME1 and MME2 and the end of Stage IV and beging of Stage V in MME3, indicating accelerated gonadal maturation with high-dose of MME3. Fatty acid composition of fertilized eggs showed no significant differences across groups in SFA, MUFA, PUFA, or HUFA levels ( ), though the MME3 group recorded slightly higher values. The results suggest MME supplementation could enhance reproductive performance and maturation in zebrafish, potentially benefiting aquaculture and experimental breeding programs.