Mechanisms of Amphibian Resistance and Sensitivity to Toxic UV Light

EPA Grant Number: R826101
Title: Mechanisms of Amphibian Resistance and Sensitivity to Toxic UV Light
Investigators: Hays, John , Blaustein, Andrew
Institution: Oregon State University
EPA Project Officer: Hahn, Intaek
Project Period: September 20, 1997 through September 19, 2000
Project Amount: $462,113
RFA: Exploratory Research - Environmental Biology (1997) RFA Text |  Recipients Lists
Research Category: Biology/Life Sciences , Aquatic Ecosystems


The objectives are to identify sensitive amphibian bioindicators for UV-light stress, to understand the role of DNA repair in amphibian UV-resistance, and to identify cellular functions that are particularly sensitive to UV stress. Hypotheses addressed: I. Due to selective pressures over evolutionary time, basal levels of photolyases that repair UV photoproducts in DNA vary more than levels of excision-repair proteins among amphibian species. II. UV and/or visible light stimulates photolyase expression. III. Low chronic UV-light supplements, which cause high mortality among frogs reared under normal room lighting, cause accumulation of UV photoproducts in DNA, peroxidation of membrane lipids, and loss of critical immune/skin functions. IV. The toxicity of weak chronic (indoor) UV light is due to the absence of solar-intensity visible light.


I. Eggs/oocytes and skins of species from 12 North American amphibian families, from a variety of habitats, will be analyzed for UV-photoproduct photolyases and excision repair proteins. II. Levels of these repair activities will be measured in animals reared inside and reared/obtained outside, using selected low-intrinsic-photolyase and high-intrinsic-photolyase species. III. Larvae/metamorphs reared indoors under weak chronic UV light will be used to measure UV photoproducts and peroxidized membrane lipids in skin tissues, resistance to pathogens, and immune functions. Light regimes will be UV-B and higher wavelengths, far UV-A and higher, near UV-A and higher, no UV. IV. Selected weak chronic UV regimes will be supplemented with strong visible light.

Expected Results:

Understanding of how selective pressures have shaped expression of UV-photoproduct photolyases and excision-repair activities. Identification of low-repair-level species at particular risk from solar UV-B increases. Understanding of effects of environmental light cues on repair-enzyme-expression. Identification of the skin-cell DNA and membrane-lipid assays, and immune-function tests, that are most indicative of UV-light toxicity; and understanding of respective responses of these to visible solar light.

Supplemental Keywords:

stratospheric ozone, ecological effects, amphibians, bioindicator species, UV-B light, UV-A light, DNA repair, UV-photoproduct photolyase, ecosystem balance, biochemistry, immunology, molecular genetics, Pacific Northwest, North America., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, amphibians, Environmental Microbiology, Biology, cell function, molecular genetics, frogs, excision-repair proteins, amphibian malformations, immune function, membrane lipid assays, photolyase expression, amphibian bioindicator, DNA repair, mortality

Progress and Final Reports:

  • 1998
  • 1999
  • Final