Potential Physiological and Molecular Mechanisms Underlying Low Viability of Gynogenetic WW-Type Super-Female Sterlet...

WW-type super-female broodstock are essential for all-female breeding in sturgeons under the ZZ/ZW sex-determination system, but their practical use is constrained by high mortality. This study investigates the underlying physiological and molecular mechanisms contributing to the reduced viability of WW-type super-female sterlet (Acipenser ruthenus) by comparing three genotypes (ZZ, ZW and WW) in terms of survival rates, oxidative stress levels, and gonadal gene expression. F₂ gynogenetic diploid juvenile sterlet with three genotypes were reared for 100 days under controlled conditions. Survival rates were recorded, and oxidative stress markers, including SOD, CAT, MDA and GSH-Px, were measured using commercially available assay kits. Gonadal gene expression profiles were analyzed using transcriptomic analysis. The results revealed that WW-type juveniles exhibited a significantly lower survival rate (64.2%) compared to ZZ-type and ZW-type fish (both 94.2%, p < 0.0001). While hepatic SOD and CAT activities did not differ among genotypes, MDA and GSH-Px levels were significantly higher in WW-type fish, suggesting enhanced lipid peroxidation and an insufficient compensatory antioxidant response. Transcriptome analysis revealed 747 significantly differentially expressed genes between WW-type super-females and normal ZZ/ZW individuals (p < 0.05), with significant enrichment in pathways related to immune regulation, receptor activity, lipid metabolism, and ferroptosis. Notably, downregulation of arachidonic acid metabolism genes (PTGS2, PTGES, PTGDS) was observed, while ferroptosis-related genes GPX4 and SLC3A2 were upregulated, suggesting that disturbed arachidonic acid metabolism, along with lipid peroxidation and ferroptosis activation, contribute to the reduced survival of WW-type super-females. These findings provide integrative physiological and transcriptomic evidence for the mechanistic basis of poor fitness in gynogenetic WW-type super-females and offer foundational data for improving the feasibility of all-female breeding in sturgeon.