Effects of High Temperature on Embryonic Development and Gut Microbial Colonization of Bufo gargarizans

Persistent global warming increases extreme high-temperature events, with destructive consequences for many organisms including amphibians. Although temperature is known to strongly shape gut microbiota structure and function, few studies have addressed whether and how high temperature affects gut microbial colonization in amphibian embryos. Here, 16S rRNA sequencing was employed to characterize gut-microbiota diversity and composition in Bufo gargarizans embryos from high temperature (HT) and control (Con) groups. Additionally, effects of the high temperature on embryonic growth and development were also assessed. Results indicated that elevated temperature significantly accelerated embryonic development (502.04 h for complete embryonic development in the Con group versus 214.04 h in the HT group), especially during the organogenesis stage, yet led to lower percent hatching and higher percent malformed ( P <0.05). Crucially, exposure to high temperature affected gut microbial colonization and altered microbial profile, characterized by lower richness (Ace index) and diversity (Shannon index), elevated relative abundances of Shewanellaceae ( Shewanella ), Aeromonadaceae ( Aeromonas ) and Bacteroidaceae ( Bacteroides ) in the HT group and marked enrichment of Pseudomonadales (Pseudomonadaceae and Pseudomonas ) in the Con group ( P <0.05). This study provides valuable insights for assessing the effects of high temperature on the embryonic development and gut microbial colonization of amphibians, which can then be placed in the broader context of climate change to explore the consequences of global warming for amphibians.