Ambient Ultraviolet B Radiation and Prevalence of Infection by Batrachochytrium dendrobatidis in Two Amphibian Species

Abstract

Chytridiomycosis, the emerging disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) is responsible for declines and extirpations of amphibian populations worldwide. Environmental covariates modify the host-Bd interaction and thus affect the ongoing spread of the pathogen. One such covariate may be the intensity of ultraviolet B (UV-B) radiation. In a field experiment conducted in Laguna Grande de Peñalara (central Spain), a mountainous region where the presence of Bd has been documented since 1997, we analyzed the potential effect of environmental UV-B (daily maximum 2.5-3.9 W/m(2) ) on the susceptibility of larvae of the common toad (Bufo bufo) to Bd. The proportion of infected individuals increased as tadpoles developed. The prevalence of Bd was significantly lower in tadpoles exposed to environmental UV-B intensities (2.94%) than in tadpoles not exposed to the radiation (9.72%). This finding mirrors that seen for a second amphibian species, the European midwife toad (Alytes obstetricans), for which conditional prevalence (i.e., prevalence of infection conditioned on the probability of a site being infected) across the Iberian Peninsula was inversely correlated with the intensity of UV-B.

Joint effects of habitat, zooplankton, host stage structure and diversity on amphibian chytrid

“…UV-A used for photorepair [47]) across a wide range of host species are needed to address this question. Currently, the only study to address this question (to our knowledge) indicates that natural UV-B exposure increased survival of Bd infected toads [13]. Further, in other alpine systems amphibians exhibit behavioural and physiological responses that, combined with natural DOC 'sunscreen', drastically reduce the deleterious effects of UVR [48,49].…”

“…We focus on infection prevalence in two native hosts that are highly susceptible to Bd (fire salamander: Salamandra salamandra and the midwife toad: Alytes obstetricans) [12][13][14]. Both species drive disease in this system [13,15]. To explain variation in infection prevalence, we examine direct and indirect factors that connect to Bd epidemics via gains and losses of zoospores [12,14,15].…”

“…Currently, however, the factors driving this pronounced variation in infection prevalence remain unknown. We focus on infection prevalence in two native hosts that are highly susceptible to Bd (fire salamander: Salamandra salamandra and the midwife toad: Alytes obstetricans) [12][13][14]. Both species drive disease in this system [13,15].…”

“…Hence, hosts and parasites in different ponds experience dramatically different UVR exposures. Based on previous evidence [13,21], solar radiation should damage Bd zoospores, thereby depressing infection prevalence via direct, damaging effects of UVR (Pathway 1A).…”

The Peñalara Mountain Meteorological Network (1999–2014): Description, Preliminary Results and Lessons Learned

“…Precipitation occurs mainly due to large and synoptic scale precipitation phenomena but with a marked orographic enhancement [15]. In recent years, this area has been subject to numerous scientific and multidisciplinary studies, such as in geomorphology [16][17][18][19][20], limnology [21][22][23], ecology [24], zoology [25][26][27][28], botanics [29][30][31][32][33][34][35][36][37][38][39][40] and meteorology and climate [7,14,15,18,[41][42][43][44][45][46][47][48].…”