PARENT SESSION
Oral Session # 94: Pathogens, Toxins, and Disease III.
Presiding: C Duffie
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 200.

Interacting effects of ultraviolet radiation and disease on the survivorship of three amphibian species.

Garcia, Tiffany^*,1, Romansic, John¹, Blaustein, Andrew¹, ¹ Oregon State University, Corvallis, OR, USA

ABSTRACT- Amphibian population declines and extinctions have been reported worldwide in recent decades. Factors contributing to amphibian population declines appear to vary from region to region. Causes may include contaminants, habitat degradation, pathogens, and atmospheric changes such as increases in ultraviolet-B (UV-B; 280-315 nm) radiation. These factors can act alone or in combination with one another. Importantly, amphibian species differ in their sensitivity to UV-B radiation, which harms amphibians in a variety of ways. UV-B radiation may be especially important when pathogens are involved because it can compromise an amphibian's ability to resist pathogenic infection. Thus, differential sensitivity to UV-B may result in interspecific differences in rates of infection from naturally occurring pathogens. We examined three anuran amphibians (Hyla regilla, Bufo boreas and Rana cascadae) as a model system to investigate the interaction between UV-B radiation and the chytrid fungus Batrachochytrium dendrobatidis, a key pathogen implicated in amphibian population declines. We studied the effects and interactions between UV-B radiation and chytrid on juveniles using a complete experimental 2x3 factorial design. Newly metamorphosed individuals were exposed to UV-B treatments (UV-B blocked, UV-B exposed) in the lab under naturally relevant exposure rates (20 microwatts/cm²) for four days (12hr: 12hr photoperiod with 5hr of UV-B exposure/day). Individuals were then placed in chytrid exposure treatments (0hrs, 12hr, 24hr). Rana cascadae showed an increase in mortality when exposed for any amount of time to chytrid (P< 0.001). We found no interaction effect, as there was 100% mortality for all Rana cascadae individuals exposed to the chytrid fungus. We found no response in Hyla regilla and Bufo boreas to both UV-B and chytrid exposure, and no interacting effects were detected. This study reveals important implications of differential susceptibility in amphibians to chytrid infection, as well as an avenue for future studies on interactions between multiple environmental factors.

Key words: ultraviolet radiation, disease, amphibian decline, interacting effects