Animals are colonized extensively by a community of microbes, which are collectively called the microbiome. These microbes mediate many physiological aspects of their animal hosts. For example, studies suggest that gut bacteria play a role in the development and maintenance of the host immune system, which likely affects their susceptibility to parasites. These interactions are complex and remain poorly understood in ecologically-relevant systems, but represent an area of research that requires further attention to fully understand disease dynamics in any system. We tested whether a disruption in the microbiome of tadpole Cuban tree frogs (Osteopilus septentrionalis) affects subsequent parasite susceptibility in juvenile frogs. To manipulate the tadpole microbiome, tadpoles were raised in one of four water treatments: pond water (control), sterile (autoclaved) pond water only, short-term antibiotics in sterile pond water, and long-term antibiotics in sterile pond water. To determine whether disrupted tadpole microbiomes affect parasite susceptibility, juvenile frogs from the manipulated water treatments were exposed to parasitic Aplectana nematodes. Juvenile Aplectana worms penetrate the frogs’ skin then travel to the colon where the worms develop and reproduce. Frog hosts can resist these parasites by producing an antibody response, which peaks at around three weeks post-infection coinciding with when the worms are establishing in the gut.
Results/Conclusions
We found that tadpoles raised in all three manipulated water treatments had a significantly different gut bacterial community structure (e.g. lower bacterial diversity) than tadpoles raised in control pond water. However, bacterial communities of juvenile frogs reared in the different water treatments did not differ significantly. We then found that frogs reared in any of the manipulated water treatments as tadpoles had three times as many worms establish in the gut compared to frogs reared in control pond water. Our results suggest that frogs with a disrupted microbiome during the tadpole stage are less resistant to parasite infection (e.g. via the immune response) compared to frogs with undisrupted microbiomes during the tadpole stage. Overall, our study suggests that the frog bacterial microbiome during development plays an important role in subsequent parasite susceptibility.