Dietary supplementation of selenium nanoparticle improves the vitellogenesis and fecundity of female zebrafish.

Selenium (Se) is an essential micronutrient that plays a critical role in supporting growth and reproductive function in fish. Nano‑selenium (nano-Se), characterized by its higher bioavailability and lower toxicity, has emerged as a promising alternative for dietary Se supplementation. Female zebrafish were fed diets containing 0, 10, or 20 μg/g nano-Se (O_0, O_10, O_20) to examine its impact on ovarian function. After 60 days of feeding, nano-Se supplementation significantly improved growth performance and fecundity, as indicated by increased body weight, gonadosomatic index (GSI), ovulated egg number, and upregulated expression of lhb. Histological analysis revealed a higher proportion of vitellogenic follicles in the ovaries of nano-Se-treated fish. Transcriptomic profiling revealed significantly enrichment in Gene Ontology (GO) terms with cellular response to estrogen stimulus and response to estrogen, which both observed in the O_0 vs. O_10 and O_10 vs. O_20 comparison groups. A series of critical genes related to gonad development and steroidogenesis were significantly up-regulated, such as vtgs, foxl2, cyp11a and hsd17b3. In conclusion, dietary nano-Se supplementation promotes ovarian development and enhances fecundity in female zebrafish, offering novel insights into improving reproductive performance in economically important aquaculture species.