Electrical stimulation-induced mucus secretion and skin transcriptome responses in Amur catfish (Silurus asotus)

Fish skin mucus is a key defensive barrier, yet its secretion and regulation remain poorly characterized in Amur catfish (Silurus asotus). Here, controlled electrical stimulation significantly enhanced mucus secretion under optimized parameters of 10 V and 15 cycles, resulting in a 3.59-fold increase in mucus-associated protein output and clear electrophoretic protein profiles. Histological and ultrastructural analyses showed a more disordered distribution of mucous cells, greater morphological heterogeneity, reduced mean mucous-cell area, and fewer intracellular granular inclusions in stimulated fish than in unstimulated controls. Serum glucose increased significantly at 6 h after stimulation but returned by 24 h to a level not significantly different from that of the control group, indicating a transient acute physiological response. Comparative transcriptomic analysis between the 10 V_15 cycles stimulated group and the 0 V_15 cycles control group identified 650 differentially expressed genes (DEGs), enriched mainly in polysaccharide metabolism, glycogen biosynthesis, and protein ubiquitination. KEGG enrichment further implicated MAPK signaling and endoplasmic reticulum (ER) protein-processing pathways as potentially involved in mucin biosynthesis, folding, and exocytosis. RT-qPCR validation of selected DEGs involved in immunity, metabolism, and cellular regulatory processes showed a strong concordance with the RNA-seq results. Together, these findings provide a novel insight into electrically stimulated mucus secretion in Amur catfish and support controlled electrical stimulation as a practical approach for mucus collection.