COS 90-6
Differences in susceptibility and sensitivity to the amphibian pathogen Batrachochytrium dendrobatidis across host ages
We are currently experiencing an extreme contraction of biodiversity across the globe. One group that has been particularly affected is amphibians. Although there are numerous factors contributing to amphibian population declines and extinctions, infectious disease has been associated with many of these losses. Chytridiomycosis, caused by the aquatic fungal pathogen Batrachochytrium dendrobatidis (Bd), is one such disease. Metamorphosis can be a stressful period for many amphibians and there is evidence to suggest that recently-post-metamorphic frogs are at the most risk to the disease. We experimentally tested the hypotheses that susceptibility to infection, infection intensity, and mortality after infection, all decrease as recently-post-metamorphic frogs age. We raised Pacific treefrogs (Pseudacris regilla) and red legged frogs (Rana aurora) to metamorphosis and subsampled individuals at various time points: approximately 1, 2, and 3 weeks post-metamorphosis and 1, 3, 5, 7, and 9 months post-metamorphosis. At each time point, we exposed individuals to the pathogen and monitored survival and infection status.
Results/Conclusions
Counter to our initial predictions, in both species survival after exposure to Bd was highest at the earliest post-metamorphic time points. Only at the later time points were the expected decreases in survival observed. When controlling for frog mass and species, prevalence of infection and intensity of infection both increased with host age. Our results suggest that for these two species of amphibians, the timing of exposure to Bd could be an important driver of disease dynamics in the chytridiomycosis system.