Comparative Intestinal Transcriptomics Reveals Sex-Dependent Physiological Signatures in Mugilogobius chulae and...

Sex is an important biological variable in animal physiology and environmental-stress research, but its influence on fish intestinal transcriptomic profiles remains insufficiently characterized. In this study, adult female and male Mugilogobius chulae were used to characterize baseline intestinal sex differences and to evaluate their relevance to short-term sulfamethoxazole exposure. Fish were assigned to solvent control or nominal 1 mg/L sulfamethoxazole exposure for 7 days, and intestinal tissues were analyzed by histology, RNA sequencing (RNA-Seq), functional enrichment analysis, gene set enrichment analysis, and quantitative real-time polymerase chain reaction validation. Representative histological sections showed qualitative sex-related differences in intestinal morphology. Transcriptomic analyses revealed that intestinal variation was more strongly associated with sex than with pooled treatment status. The pooled female-versus-male comparison identified 85 differentially expressed genes, whereas the pooled treatment-versus-control comparison yielded no significant differentially expressed genes under the current threshold. Functional enrichment and gene set enrichment analyses showed that female-biased intestinal profiles were mainly associated with nutrient absorption, lipid and sterol handling, membrane transport and epithelial interface-related pathways, whereas male-biased profiles were more closely related to RNA processing, oxidative metabolism, translation, protein targeting and mucosal immune signaling. These findings demonstrate sex-dependent intestinal transcriptomic signatures in M. chulae and support sex-aware intestinal transcriptomic analysis in aquatic animal omics and environmental-stress evaluation.