Arachidonic Acid Enhances Reproductive Performance and Oocyte Quality of Female Blotched Snakehead (Channa maculata) via Activation of the TGF-β/Smad Signaling Pathway

Arachidonic acid (ARA) is an indispensable fatty acid for aquatic organisms, playing critical roles in reproductive physiology. This study aimed to evaluate the effects of graded dietary ARA levels on the reproductive performance, tissue fatty acid profiles, plasma sex hormone and prostaglandin concentrations, ovarian molecular responses, and offspring larval quality in female blotched snakehead (Channa maculata). Three experimental diets with ARA levels of 0% (control, C), 1.5% (ARA1.5), and 3.0% (ARA3.0) were formulated and administered to female blotched snakehead for 12 weeks. The results demonstrated that dietary ARA supplementation significantly improved fertilization rate, hatching rate, and larval growth performance, while reducing the larval malformation rate. ARA supplementation enhanced the deposition of ARA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) in both ovaries and muscle tissues. Plasma levels of sex hormones and prostaglandins (PGE2, PGF2α) were significantly elevated with increasing dietary ARA concentrations. Furthermore, qRT-PCR and Western blot results indicated that ARA supplementation upregulated the expression of genes and proteins in the TGF-β/Smad signaling pathway and steroidogenesis-related genes. Metabolomic analysis identified differential metabolites enriched in arachidonic acid metabolism, the VEGF signaling pathway, and glycolysis/gluconeogenesis in ovaries and larvae, with ARA-derived eicosanoids significantly upregulated. Dietary ARA supplementation was associated with improved reproductive performance, accompanied by reproducible molecular alterations in the ovarian TGF-β/Smad signaling pathway, indicating that this cascade represents a plausible underlying regulatory mechanism for this improvement.