Integrated transcriptome and weighted gene co-expression network analyses reveal hepatic metabolic response of largemouth bass (Micropterus salmoides) under hypertonic stress

Largemouth bass (Micropterus salmoides) is a valuable freshwater species with a high market value in China. Previous studies have suggested that this fish can be cultured in brackish water. However, there is still a lack of detailed information about the changes in energy metabolic pathways in largemouth bass under hyperosmotic stress. In this study, we conducted a comparative analysis of the growth performance and liver transcriptomes of largemouth bass cultured at a range of salinity levels (0 ‰, 3 ‰, 6 ‰, 9 ‰, and 12 ‰). A comprehensive analytical approach encompassing differential gene expression analysis and weighted gene co-expression network analysis demonstrated that protein metabolism, glycolysis, the tricarboxylic acid cycle, fatty acid oxidative catabolism, and oxidative phosphorylation pathways play pivotal roles in the response of largemouth bass to hyperosmotic stress. Our results show that the main energy metabolic patterns of largemouth bass changed as the salinity level increased, and the energy demands were met by a combination of multiple energy metabolic pathways. Fish in the 3 ‰ salinity group showed the highest WGR and fat deposition, whereas salinity at 12 ‰ had severe toxic effects on fish physiology, including growth inhibition and oxidative damage to the liver (Significant upregulation of antioxidant-related genes included gpx and gsr). In conclusion, the remodeling of fish energy metabolism under differing salinities ultimately affects growth. Our findings offer a new perspective on the impact of hyperosmotic stress on the growth of largemouth bass and establish a foundation for enhancing the adaptation of this species to brackish water environments.