UV-B radiation and temperature effects on striped marsh frog
Researcher:

Lesley Alton

Since the discovery of the ozone hole over Antarctica, stratospheric ozone depletion and the corresponding increase in terrestrial UV-B radiation have become a global concern. Rising UV-B levels have been linked with an increase in the incidence of skin cancers in humans, but less is known about the effects on other species. UV-B radiation has been implicated as a potential causal agent in the global decline and loss of numerous amphibian species. There is mounting evidence to suggest that UV-B can negatively impact on amphibians either through direct, sublethal, or synergistic effects (i.e. in concert with environmental contaminants and diseases). Using striped marsh frog, Limnodynastes peronii, as a model species, we have demonstrated that UV-B effects are temperature dependent with UV-B damage showing a marked increase at cooler temperatures. With most declines occurring at high altitudes where UV-B irradiance is greater and temperatures lower, our work gives credence to the hypothesis that increasing UV-B may be a contributing factor to global amphibian declines.

Our research into the interactive effects of UV-B and temperature is currently ongoing with our focus turning to the thermal plasticity of DNA repair mechanisms. DNA is the primary target of UV-B damage with UV-B resulting in the formation of covalent linkages between adjacent pyrimidine nucleotide bases. Formation of these dimers inhibits proper replication and transcription and thus poses a threat to the viability and functional integrity of cells. An important process by which DNA is repaired is through enzymatic photoreactivation, which is catalysed by enzymes known as photolyases. Given that enzymatic processes are temperature dependent, it is likely that the observed increase in detrimental UV-B effects on larval L. peronii at lower temperatures is due to the reduced rate of enzymatic repair. We will be investigating this directly by measuring photolyase gene expression and photolyase activity in L. peronii at different temperatures.