Something in the water: Aquatic microbial communities influence the larval amphibian gut microbiota, neurodevelopment, and behavior

Microorganisms colonize the gastrointestinal tract of animals and establish symbiotic host-associated microbial communities that influence vertebrate physiology. More specifically, these gut microbial communities influence neurodevelopment through the microbiota-gut-brain (MGB) axis. We tested the hypothesis that larval amphibian neurodevelopment is affected by the aquatic microbial community present in their housing water. Newly hatched Northern Leopard Frog (Lithobates pipiens) tadpoles were raised in pond water that was unmanipulated (natural) or autoclaved. Tadpoles raised in autoclaved pond water had a gut microbiota with reduced bacterial diversity and altered community composition, had decreased behavioral responses to sensory stimuli, were larger in overall body mass, had relatively heavier brains, and had altered brain shape when compared with tadpoles raised in natural pond water. Further, the diversity and composition of the gut microbiota was associated with tadpole behavioral responses and brain measurements. Our results suggest that aquatic microbial communities shape tadpole behavior and brain development, providing strong support for the occurrence of the MGB axis in amphibians. Lastly, the dramatic role played by aquatic microbial communities on vertebrate neurodevelopment and behavior should be considered in future wildlife conservation efforts.