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.