Meeting Abstract
A clearer understanding of how changes in the environment affect the immune defenses of animals is needed in order to predict the impact and dynamics of emerging wildlife diseases. Due to its dramatic effects on the physiology of animals, their microbiomes, and their pathogens, temperature may be a key variable modulating the level of protection an animal’s defenses can provide. We investigated how temperature and two cutaneous defenses, the skin microbiome and antimicrobial peptides, affect the susceptibility of frog hosts to infection by the causative agent of amphibian chytridiomycosis, Batrachochytrium dendrobatidis (Bd). To do this, we manipulated either the bacterial community or antimicrobial peptides present in the skin mucus of susceptible hosts prior to exposing them to Bd under two different ecologically relevant temperatures. We predicted that frogs with reduced skin bacterial communities and antimicrobial peptides would be more susceptible (i.e., less resistant to and/or more tolerant of Bd infection) than frogs with intact or augmented (by addition of a known antifungal bacterium) mucosal defenses. However, we also predicted that these interactions would be temperature dependent, with higher temperatures increasing the protective capabilities of skin defenses. While temperature alone seems to have impacted the likelihood and intensity of Bd infection, a frog’s ability to survive (i.e., tolerate) a heavy Bd infection was best explained by interaction between temperature and the cutaneous bacterial community. Both temperature and exposure to Bd affected the production of antimicrobial skin peptides, with frogs at higher temperatures producing more peptides and also surviving longer with a heavy Bd infection. These results may have important implications for the disease mitigation strategies for amphibians and other taxa threatened by disease in a changing climate.
