The depletion of ozone layer increases the amount of harmful ultraviolet-B (UVB) radiation reaching the Earth's surface. Increments in UVB may trigger amphibians' decline, as they cause negative effects on these animals: malformations, genotoxic effect (DNA damage), decreased growth, increased mortality and distorted swimming performance. However, several biotic and abiotic factors can protect amphibians from UVB damage (water color and depth, melanin in epithelial tissue, removal and repair mechanisms of DNA lesions). Temperature may also play a major role on the UVB effects, as enzyme activity is likely reduced at low temperatures. Finally, the distribution of a given population may determine the amount of UVB exposure. In this context, the present project aims to investigate the effects of exposure to different intensities of UVB and temperature on the development of tadpoles from three populations of genus Rhinella, distributed along an altitudinal gradient. We expect that populations from high lands (exposed to higher UVB and lower temperature in their natural habitat) will have lower mortality rate when acclimated to our experimental treatment than the populations from low lands. Also, during treatment we expect that these populations will have less DNA damage, given that they will have higher photolyase activity, and the effects on swimming speeds and growth rate will be smaller than those observed in lowland populations. To test these hypotheses, we will acclimate the tadpoles at different temperatures and UVB radiation throughout their development. Swimming performance, analyses of DNA damage and repair, and morphological measurements will be recorded at three developmental stages, in order to test for differences in sensitivity among populations and verify the influence of temperature on the UVB effects.
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