Physiological and transcriptomic insights into the stress response of mud crab Scylla paramamosain (Estampador, 1950)...

Salinity is a critical abiotic factor regulating the physiological homeostasis of aquatic crustaceans. To elucidate the physiological and molecular mechanisms underlying the adaptation of the mud crab Scylla paramamosain (Estampador, 1950) to low salinity, individuals were exposed to low salinity (3‰) and control (28‰) conditions for 7 days. Physiological assays revealed that low salinity stress induced significant oxidative stress and tissue damage in the hepatopancreas, characterized by significantly increased activities of SOD (increased by 32.27%), CAT (increased by 56.23%), T-AOC (increased by 152.68%), and AST (increased by 24.77%). Transcriptomic analysis identified 489 differentially expressed genes (DEGs), comprising 268 up-regulated and 221 down-regulated genes. Functional enrichment analysis demonstrated that mud crab acclimates to the hypotonic environment by enhancing transmembrane ion transport and synchronously activating "Arginine and proline metabolism" to modulate intracellular organic osmolytes. Concurrently, the significant activation of the p53 signaling pathway suggests a critical defense mechanism employed to mitigate oxidative damage and regulate apoptosis. These findings provide comprehensive insights into the metabolic remodeling and stress response strategies of mud crabs under low salinity stress.