Effects of chronic high-temperature stress on muscle tissue integrity and metabolism-related genes in Clarias fuscus

The increasing prevalence of high-temperature days due to global warming presents significant challenges for aquatic ecosystems and aquaculture practices. This study investigates the effects of chronic high-temperature stress on Clarias fuscus, a catfish species native to subtropical and tropical regions. The fish were cultured for 90 days under high-temperature conditions (HT, 34 °C) and normal temperature conditions (CT, 26 °C). Histological and transcriptomic analyses were conducted to assess the impact of continuous high-temperature stress on muscle tissue. Histological examination revealed significant damage in the HT group, characterized by irregular tissue arrangement, widened muscle fiber gaps, broken muscle filaments, and cracked nuclei. Transcriptomic analysis identified 975 differentially expressed genes (DEGs) in muscle tissue under high-temperature stress, with 512 genes up-regulated and 463 down-regulated. Notably, heat shock protein (Hsp) family genes, including Hsp40, Hsp70 and Hsp90, were significantly up-regulated under heat stress. Enrichment analysis of these DEGs revealed significant alterations in protein processing, the PPAR signaling pathway, and fatty acid oxidation and metabolism within the endoplasmic reticulum. These findings suggest that C. fuscus experiences substantial tissue damage and a reduced metabolic response under high-temperature stress. This study provides a scientific foundation for future research on the adaptability of fish to temperature fluctuations.