Effects of artificial light at night on basal thermogenesis and gut microbiota in two small passerine birds

With the acceleration of urbanization, artificial light at night (ALAN) has emerged as a rapidly increasing environmental pollutant worldwide, significantly impacting the physiological processes of animals. Species with different life-history traits may exhibit varying metabolic responses to ALAN; however, the underlying mechanisms remain largely unexplored. Our study investigated the impact of ALAN on basal thermogenesis in two avian species with different life-history traits, zebra finches (Taeniopygia guttata) and Bengalese finches (Lonchura striata domestica), focusing on the changes in phenotypic, molecular and microbiota responses. Birds were exposed to 5 lx ALAN for 4 weeks, during which their energy budget, basal metabolic rate (BMR), serum hormone level, thermogenic gene expression and gut microbiota composition were assessed. ALAN significantly reduced BMR and triiodothyronine (T3) levels in zebra finches, impairing thermogenic functions in the hypothalamus and muscle tissues. In contrast, Bengalese finches showed no changes in BMR and T3 levels. Moreover, ALAN decreased gut microbiota α-diversity in zebra finches, disrupting microbial functions related to basal thermogenesis and circadian regulation, while Bengalese finches maintained a relative stable gut microbiota composition and diversity. In conclusion, our study reveals that the two bird species showed distinct thermogenic responses to ALAN at molecular, biochemical and physiological levels. Our findings indicate that ALAN drives physiological differences between the two bird species by altering the composition of the gut microbiota, which regulates basal thermogenesis and energy metabolism, highlighting its impact on host-microbiota interactions and metabolism.