Abstract:
In the present study we investigated the potential of natural solar radiation to alter the toxicity of a
commonly used carbamate pesticide, carbofuran, on tadpoles of the Common Asian Toad Duttaphrynus
melanostictus. A single exposure trial was conducted over 96 hrs with three concentrations (150, 250
and 500 μgl-1) of photo-irradiated and non-irradiated carbofuran. Results show that photo-irradiation
markedly reduced the toxicity of carbofuran as evident by its effects on three end points, i.e. mortality,
growth and swimming activity. The mortality of tadpoles exposed to irradiated carbofuran was
significantly lower than those exposed to the non-irradiated pesticide. Both treatment and control tadpoles
showed a hormetic response for mortality. Tadpoles in irradiated tanks were also larger and more active
than those in the control tanks. Photo-altered toxicity was evident at all three tested concentrations. The
results of this study therefore signals caution when directly linking results of empirical trials to field
scenarios and highlight the necessity to evaluate toxic effects of compounds under variable environmental
conditions.
