Divergent metabolic strategies under food limitation reveal physiological adaptive advantages of invasive Trachemys scripta elegans over native turtles.

Food limitation is a common ecological challenge for freshwater organisms and may have differential impacts on the performance of native and invasive species. The physiological and biochemical mechanisms for interspecific tolerance to food shortage remain poorly understood. Here, we compared serum and liver biochemical parameter, relative expression of genes related with carbohydrate and lipid metabolism, and metabolomic profile in two freshwater turtles, invasive Trachemys scripta elegans and native Mauremys sinensis, under prolonged food limitation to evaluate its differential effects between these species. Body mass loss under starvation was pronounced in M. sinensis, but minimal in T. scripta elegans. Food limitation reduced hepatosomatic index in both species, indicating the mobilization of liver energy reserves. Differential impact on serum glucose and lipid changes between species might indicate divergent substrate utilization strategies. Food limitation induced coordinated regulation of genes involved in gluconeogenesis, fatty acid oxidation, and energy sensing pathways, accompanied by increased liver AMPK and CPT1 contents, particularly in T. scripta elegans. Live metabolomic analysis revealed broad perturbations in lipid and amino acid metabolism in M. sinensis, whereas more focused regulation of energy metabolic pathways in T. scripta elegans, potentially reflecting differential metabolic reprogramming. Collectively, our results demonstrate that higher metabolic flexibility and tighter regulation of energy metabolic pathways enable invasive turtles to better tolerate food limitation, and provide mechanistic insights into how physiological and metabolic traits contribute to invasion success under resource-limited environments.