Ancient behaviors of larval amphibians in response to an emerging fungal pathogen, <Emphasis Type="Italic">Batrachochytrium dendrobatidis</Emphasis> |
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Authors: | Barbara A Han Paul W Bradley Andrew R Blaustein |
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Institution: | (1) Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA |
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Abstract: | Behaviors have evolved in response to various selection pressures over evolutionary time. However, not all behaviors are adaptive.
Some presumably “ancient” behaviors, persistent for millions of years, may be detrimental in the face of novel selection pressures
in modern times. These pressures include a multitude of emerging infectious diseases which may be stimulated by environmental
changes. We examined how a globally emerging amphibian pathogen, Batrachochytrium dendrobatidis (BD), affected two key evolutionarily persistent behaviors displayed by amphibian larvae: aggregation and thermoregulation.
Larval aggregation behavior is often essential for foraging, thermoregulation, and antipredator defense, but varies among
species. Thermoregulatory behavior speeds larval development in ephemeral habitats. Specifically, we examined whether aggregation
and thermoregulatory behaviors changed when exposed to the BD pathogen in two species (Bufo boreas and Rana cascadae) whose larvae aggregate in nature. In laboratory choice tests, larvae of neither species avoided infected conspecifics. BD-exposed
B. boreas larvae aggregated, while unexposed R. cascadae larvae associated more frequently with BD-exposed conspecifics. There was no evidence of behavioral fever or altered thermoregulation
in larvae of four species we examined (Pseudacris regilla, Rana aurora, B. boreas, R. cascadae). The absence of behavioral fever may suggest an inability of the larvae of some host species to mediate infection risk by
this pathogen. Thermoregulatory behaviors may exhibit a high degree of evolutionary inertia in amphibian hosts because they
are linked with host physiology and developmental rates, while altered aggregation behaviors could potentially elevate pathogen
transmission rates, leading to increased infection risk in social amphibian species. |
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Keywords: | Tadpoles Aggregation Schooling Thermoregulation Chytridiomycosis |
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