Animals are colonized extensively by a community of microbes, which are collectively called the microbiota. Studies suggest that gut bacteria play a role in the development and maintenance of the host immune system, which likely affects their resistance to parasites. For example, our previous work demonstrates that an early-life disruption in the host-associated microbiota increases infection risk in frogs. However, we know little about how "real world" environmental stressors, such as pollutants, play a role in these interactions. We tested whether the early-life gut microbiota mediates the effect of pollutants on later-life infection risk in Cuban tree frogs (Osteopilus septentrionalis). Tree frog tadpoles were assigned to one of four chemical treatments crossed with either sterile pond water (to manipulate the microbiota) or non-sterile pond water media. For the chemical treatments, tanks received chlorothalonil (1.64 µg/L), chlorpyrifos (6.68 µg/L), imidacloprid (11.9 µg/L), or solvent (control) for 7 days. After metamorphosis, frogs were exposed to parasitic gut nematodes Aplectana.
Results/Conclusions
Worms were 5-6 times more prevalent in frogs reared in polluted pond water compared to pond water controls. Worms were similarly more prevalent in frogs reared in polluted and non-polluted sterile water compared to pond water controls. Thus, our results suggest that the early-life microbiota mediates the effect of pollutants on later-life infection risk.