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Ultraviolet radiation (UVR) is one of the most damaging natural exogenous factors which exists on our planet, since it can affect many fundamental biological functions of living organisms^7. When unresolved or when excessive, exposure to UVR can lead to erythema⁴, skin cancer, immunosuppression and fotoaging². Although the release of ozone-depleting substances was halted in the past decades, the amount of UVR that reaches our earth's surface continues to increase, and will continue to do so until the ozone holes are recovered^1,7. Currently, it is estimated that the annual global stratospheric ozone loss is approximately 3%⁶. In this context, investigating the effects that UVR can exert on natural populations is relevant, mainly because of the deleterious effects that have been reported in a number of species^3,7 and, particularly, in marine and freshwater ecosystems⁹. We recently reported that UVR-induced lesions are prevalent in large whales. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus) and sperm whales (Physeter macrocephauls) sampled within the Gulf of California, Mexico, showed clear evidence of epidermal damage associated with acute and severe sunburn⁵. Histological abnormalities included intracellular oedema, cytoplasmic vacuolization, glycogen deposition, microvesicles and infiltration of leukocytes⁵. Pigmentation differences between the three species, and the time remaining on the surface, were the main drivers for quantitative differences in individual skin lesions⁵. Those results suggested that sustained exposure to UVR due to thinning of the ozone layer is a significant and plausibly growing threat to the health of large whales. Furthermore, we found evidence of distinct mechanisms to counteract UVR-induced damage, particularly that of overexpression of pigmentation pathways in the blue whale⁵. In the context of global environmental change, species will tend to adapt and thus modify their dispersion habits, behavior or physical characteristics, depending on the plasticity of these traits⁷. Keeping in mind that plasticity is costly⁸, it is relevant to understand the constraints and genetic basis of phenotypic responses to UVR which may be under selection. Using a sample archive of 106 blue whale skin biopsies and a photocatalogue of 750 blue whales photographed between 1996 and 2012, we will take our previous findings further by cuantifying and investigating changes in individual pigmentation at different points in their life and throughout a particular season. Using state-of-the-art genetic and gene expression technologies, it will be possible to quantify the amount of photoproducts in whale DNA and quantify the expression of UV-damage repair enzymes. By adding our study to previous findings, our results will help to predict negative effects of global environmental changes on the viability of natural populations⁹.

Palabras clave: Whales; Ultraviolet radiation

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