Comparative Transcriptomic Analysis of Male and Female Gonads in the Zig-Zag Eel (Mastacembelus armatus)

The zig-zag eel (Mastacembelus armatus) is a unique economic fish species in China and exhibits significant dimorphism of male and female phenotypes. Cultivating all-male seedlings can significantly improve production efficiency. To investigate sex differentiation and gonadal development in M. armatus, high-throughput sequencing technology was used to analyze the transcriptomes of male and female gonads at different developmental stages, both before and after sex differentiation. We identified key genes involved in sex differentiation, male-specific differentially expressed genes (DEGs), including dmrt1, amh, sox9, gsdf, and dmrt2b, and female-biased DEGs, including foxl2, rspo1, gdf9, bmp15, and wnt4. GO and KEGG enrichment analyses revealed that signaling pathways such as MAPK, Wnt, and TGF-β play significant roles in sex differentiation in M. armatus. The expression levels of 13 sex-related genes, including dmrt1, sox9, amh, foxl2, rspo1, and wnt4, were determined by RT–qPCR in addition to RNA sequencing. RT-qPCR validation results were consistent with the transcriptomic data, confirming the reliability of our findings. This research provides valuable insights into the mechanisms of sex differentiation in M. armatus and lays a foundation for developing all-male populations in aquaculture.