The Immune-Antioxidant Trade-Off Mediated by Actinobacteria Drives Niche Differentiation: Physiological and Gut Microbiota Responses of Two Cold-Adapted Brown Frog Species to Contrasting Peak Daily Habitat Temperatures.

The fluctuating temperature poses challenges to the survival of amphibians. This study employed two cold-adapted brown frog species, Rana dybowskii and Rana amurensis, from high-latitude cold regions as research models. We explored the mechanism by which contrasting peak daily habitat temperatures affect their physiological function and symbiotic microbial community. The results indicate that these two cold-adapted brown frog species exhibit a common physiological response of enhanced immune capacity and suppressed antioxidant capacity when subjected to elevated temperatures. However, they demonstrate unique coping strategies and physiological regulatory effects on gut microbiota: R. dybowskii activates its immune system by reducing the abundance of Actinobacteria and inhibiting metabolic pathways, but the decrease in Bacteroidetes abundance impairs antioxidant efficacy. On the other hand, R. amurensis experiences impairment of antioxidant function due to the regulatory effects of a significant increase in Proteobacteria and Actinobacteria, a marked decrease in Bifidobacterium, and a decline in gut microbiota α-diversity. For the first time, this study reveals the adaptive mechanisms by which two cold-adapted amphibian species respond to the contrasting peak daily habitat temperatures, providing a scientific basis for understanding how ectotherms react to climate change and for predicting their population dynamics.