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Dynamics of an Emerging Infectious Disease in Amphibians: From Individuals to Communities

EPA Grant Number: MA916980
Title: Dynamics of an Emerging Infectious Disease in Amphibians: From Individuals to Communities
Investigators: Venesky, Matthew D.
Institution: University of Memphis
EPA Project Officer: Jones, Brandon
Project Period: September 1, 2008 through August 31, 2011
RFA: GRO Graduate Fellowships (2008)
Research Category: Academic Fellowships

Description:

Objective:

Chytridiomycosis is an emerging infectious disease of amphibians caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd) and has played a role in the decline of amphibian populations. My main research objective is to understand how Bd affects the foraging activity and efficiency of larval anurans with different life histories, how Bd is transmitted between individuals, and the effects of Bd at the population and community levels. For my experiments, I will use two species of tadpoles—Grey Treefrogs (Hyla versicolor) and Fowler’s Toads (Bufo fowleri). These two species differ in behaviors associated with how and where they feed within ponds, which may impact disease transmission and/or host fitness.

Approach:

I will test for the potential of indirect, intraspecific, transmission by water between infected and susceptible larvae. For each species, my design will be a 3 X 2 full factorial design consisting of 6 treatments--3 distances (0, 30, and 100 cm) fully crossed with 2 trial durations. My null hypothesis is that disease transmission requires direct contact between infected and susceptible animals and my alternative hypothesis is that susceptible animals can be infected by free-swimming zoospores.

To test for differences in foraging activity and efficiency, I will conduct experiments examining the effects of Bd infection on larval foraging time and efficiency through ontogeny. In these experiments, I will observe the foraging behavior and examine the foraging efficiency of tadpoles of both species.

In my final two projects, I will study the effects of Bd transmission rates at the population and community levels. I will manipulate the presence or absence of Bd using a common garden approach and I will also manipulate the proportion of infected larvae and collect data throughout the length of the experiment on transmission rates, pathogen load, and effects on life history traits through ontogeny. My null hypothesis is that regardless of the initial density of infected larvae, there will be no difference in the direction of transmission between the two species. My alternative hypothesis is that that there will be different interspecific transmission rates between the two species at both the population and community levels.

Expected Results:

For the transmission experiment, I predict that Bd will be transmitted to susceptible tadpoles at both the 0 and 30 cm distances. For my foraging experiments, I predict that Bd infected larvae will spend less time foraging compared to non-infected larvae and that infected larvae will be less efficient at foraging. For my population and community experiments, I predict that there will be a faster intraspecific transmission within B. fowleri and that more B. fowleri larvae will become infected, irrespective of the initial starting density of infected individuals.

Supplemental Keywords:

amphibian, anuran, behavior, disease ecology, life history, pathogen transmission,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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