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bioRxiv · 10.1101/165985

Shifts in temperature influence how Batrachochytrium dendrobatidis infects amphibian larvae

Bradley, P. W.·Brawner, M. D.·Raffel, T. R.·Rohr, J. R.·Olson, D. H.·Blaustein, A. R.
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Abstract

Many climate change models predict increases in mean temperature, and increases in frequency and magnitude of temperature fluctuations. These potential shifts may impact ectotherms in several ways, including how they are affected by disease. Shifts in temperature may especially affect amphibians, a group with populations that have been challenged by several pathogens. Because amphibian hosts invest more in immunity at warmer than cooler temperatures and parasites may acclimate to temperature shifts faster than hosts (creating lags in optimal host immunity), researchers have hypothesized that a temperature shift from cold-to-warm might result in increased amphibian sensitivity to pathogens, whereas a shift from warm-to-cold might result in decreased sensitivity. Support for components of this climate-variability based hypothesis have been provided by prior studies of the fungus Batrachochytrium dendrobatidis (Bd) that causes the disease chytridiomycosis in amphibians. We experimentally tested whether temperature shifts before Bd exposure alter susceptibility to Bd in the larval stage of two amphibian species - western toads (Anaxyrus boreas) and northern red legged frogs (Rana aurora). Both host species harbored elevated Bd infection intensities under constant cold (15{degrees} C) temperature in comparison to constant warm (20{degrees} C) temperature. Additionally, both species experienced an increase in Bd infection abundance when shifted to 20{degrees} C from 15{degrees} C, compared to a constant 20{degrees} C but they experienced a decrease in Bd when shifted to 15{degrees} C from 20{degrees} C, compared to a constant 15{degrees} C. These results are in contrast to prior studies of adult amphibians that found increased susceptibility to Bd infection after a temperature shift in either direction, highlighting the potential for species and stage differences in the temperature-dependence of chytridiomycosis.

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Bradley, P. W., Brawner, M. D., Raffel, T. R., Rohr, J. R., Olson, D. H., Blaustein, A. R.. 2017-07-20. Shifts in temperature influence how Batrachochytrium dendrobatidis infects amphibian larvae. https://doi.org/10.1101/165985

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