Savannah River Site, South Carolina
Physiology of an imperiled amphibian, the eastern hellbender
The decline of the hellbender in North America embodies many of the characteristics surrounding the plight of amphibians around the world. Hellbenders are exposed to disease, parasites, habitat modification, altered climate, and contaminants. Unfortunately, hellbenders are also persecuted by humans for various reasons. Because hellbenders flourish in well-oxygenated mountain streams with low levels of siltation, we shouldn't view hellbenders as a nuisance, but as indicators of stream health. We can be proud of the quality of our streams when healthy hellbender populations are present! Despite the dramatic declines of eastern hellbenders and the listing of the Ozark subspecies, we know little about the basic physiology of hellbenders. However, to best conserve healthy hellbender populations and rehabilitate threatened populations it is imperative that we understand how hellbenders respond physiologically to changes in their environment. To this end, our research has focused on how ecto- and endo-parasites influence hellbender physiology.
Incubation temperature as a parental effect in birds
Parental behavior and physiology can influence offspring development and play a critical role in determining offspring phenotype. These non-genomic contributions, referred to broadly as parental effects, can ultimately shape the life history trajectory of offspring by influencing growth rates, age at maturity, survival, and reproduction. In birds, parental incubation, consisting of on- and off-bouts, determines much of the early developmental environment, influencing both the humidity and temperature under which the eggs develop. Optimal incubation temperatures become compromised when parents spend time away from the nest leading to greater predation risks and lower hatching success of eggs. Despite a long understanding of risks to hatching success, the consequences of subtle variation in incubation temperature for avian phenotype are just being explored. Using Wood Ducks as a model sytem we have demonstrated that lower incubation temperatures alter many phenotypic traits that have implications for duckling survival. Currently, we are exploring potential mechanisms for the effects of incubation temperature on phenotype and designing studies to elucidate whether incubation temperature is an important selective factor for avian life history traits (e.g., clutch size and mating systems).
Disease-medited parental effects
Long before we are born we are influenced by the environment. Parental and even grandparental exposure to contaminants, food conditions, and disease can modify our physiology and behavior. Understanding what components of our ancestor’s environment shapes our phenotype and how these effects are transmitted will transform our understanding of evolutionary processes. We are focusing on how the parental disease environment shapes the parent's reproductive behaviors, the developmental environment of their embryos, and the phenotype of their offspring
Interactions between stress and immune responses
Chronic stress, potentially through its influence on glucocorticoids like corticosterone, is thought to have negative consequences for immune function. While corticosterone may directly inhibit immune cells, chronic stress may also influence allocation of energy, ultimately shifting resources away from the immune system. If so, then the effects of chronic stress on immune responses may be greater during costly life history stages. We are investigating how chronic stress influences healing after a small biopsy , the ernegetic cost of healing, and whether healing and energy expenditure differ with life history stage. By monitoring corticosterone concentrations we will also determine whether glucocorticoids, in part, mediate effects of stress on immune processes.
Sublethal effects of exposure to common environmental contaminants
In birds and snails we are using a bioenergetic framework to translate the effects of exposure to environmental contaminants from cells to organisms to populations. We are currently working with waste water treatment effluent and MC252 crude oil from the Deepwater Horizon Oil Spill. We are using model organisms to test our questions because we can simultaneously study multiple levels of effects (e.g., cellular stress and organismal performance) over time allowing us to capture when effects arise and when individuals recover. Further, model organisms thrive in laboratory environments and reduce the need to sample individuals in wild populations.