Meeting Abstract
Amphibians are declining worldwide and are currently regarded as one of the most threatened classes of vertebrate animals. Many of these declines are due to the disease chytridiomycosis, which is caused by the fungal pathogen, Batrachochytrium dendrobatidis (“Bd”). In many parts of the world, infection patterns and disease dynamics of chytridiomycosis exhibit seasonal fluctuations. Previous studies have primarily focused on seasonal temperature effects on Bd (i.e., how temperature can limit Bd growth), while few investigations have focused on seasonal shifts in host immune responses. We conducted seasonal (wet and dry) post-epidemic surveys in 2013-2014 in two populations of the Common Rocket Frog (Colostethus panamensis), a species known to be susceptible to chytridiomycosis. We sampled for the prevalence and intensity of the pathogen (Bd), recorded microhabitat temperatures and collected skin secretions to test for the efficacy of host immune defenses (Anti-microbial peptides; AMPs) across seasons. We found clear seasonal patterns in the ability of the AMPs to inhibit Bd growth in laboratory challenge experiments. Specifically, the AMPs collected from C. panamensis during the dry seasons were more effective at inhibiting Bd growth than those collected during the wet seasons and predicted host infection status better than microhabitat temperatures. These results suggest that seasonal differences in immune effectiveness against Bd may be playing an important role in seasonal disease dynamics in chytridiomycosis.
