Liver Antioxidant, Transcriptomic and Metabolomic Responses to Heatwaves in an Aquatic Turtle Species, Pelodiscus sinensis

The physiological and metabolic responses of juvenile Chinese softshell turtles, Pelodiscus sinensis, exposed to single or double heatwaves (33 °C for 4 days) were investigated based on liver antioxidant assay and transcriptomic and metabolomic analyses. Heatwave exposure increased superoxide dismutase and catalase activities, but did not significantly alter malondialdehyde and reactive oxygen species levels, indicating enhanced antioxidant defense. Transcriptomic analysis revealed the differential expression of genes involved in carbohydrate metabolism, immune function, cardiovascular regulation, and signal transduction, with more pronounced alterations in single-heatwave-exposed turtles. Additionally, metabolic dysregulation in amino acids was revealed by significantly altered levels of some key amino acids and their derivatives. Compared with single-heatwave-exposed turtles, fewer differentially expressed genes and less metabolic disruptions in double-heatwave-exposed turtles probably indicated less physiological disorders under recurrent heat stress. Although P. sinensis can adopt physiological and metabolic adjustments to mitigate the adverse effects of short-term heatwaves, repeated heatwave exposure might still cause severe physiological consequences in aquatic turtles. These findings may have important implications for the conservation of freshwater turtle species under future climate change scenarios.