Whole-genome resequencing and transcriptomes analysis of hermaphroditism mechanisms in silver pomfret (Pampus argenteus): The role of feeding and lipid metabolism

Our previous research revealed that silver pomfret (Pampus argenteus) undergoes early oocyte apoptosis during testicular differentiation, accompanied by juvenile hermaphroditism. However, the underlying causes and molecular mechanisms of these processes are not fully understood. In this study, we integrated whole-genome resequencing and genome-wide association study from both sexes, revealing the absence of distinct sex chromosomes or sex-specific molecular markers in silver pomfret. Lipid metabolism analysis showed that stage I males exhibited significantly lower lipid metabolism levels than stage I females and stage II males, with a notable metabolic recovery observed in stage II males. These findings suggest that fish with reduced lipid levels are more likely to differentiate into males. Furthermore, controlled dietary intake experiments resulted in a male-biased sex ratio, indicating that nutrition can affect gonadal differentiation through its effects on lipid metabolism. Some fish exhibited prolonged hermaphroditism after sexual differentiation. Transcriptomic analysis of the hypothalamus and gonads suggested that metabolic abnormalities may contribute to this phenomenon. Comparative lipid metabolism analysis among females, males, and hermaphrodites revealed that hermaphroditic fish had significantly higher lipid metabolism than male fish, highlighting metabolic imbalance as a key factor contributing to hermaphroditism. Additionally, total cholesterol, gonadotropin-releasing hormone, follicle-stimulating hormone, testosterone, and 11-ketotestosterone were differentially expressed across phenotypes, with genes associated with both testicular and ovarian differentiation being highly expressed in the gonads of hermaphrodites. These results indicate that lipid metabolism affects cholesterol levels, which subsequently affect sex hormone concentrations and the expression of sex differentiation genes, potentially explaining the persistence of hermaphroditism. In summary, this study revealed that nutritional conditions regulate lipid metabolism, thereby affecting the direction of gonadal differentiation in silver pomfret. These findings imply that environmental sex determination in fish could be managed by modulating lipid metabolism, offering a new strategy for controlling the sex ratios in aquaculture.