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Influencia diferencial de la expresión de Slc7a11 y la condición corporal sobre la pigmentación producida por feomelanina en dos poblaciones de trepador azul Sitta europea con diferente riesgo de depredación

The expression of the gene Slc7a11 promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the pigment pheomelanin synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. Therefore, this study hypothesized that a mechanism limiting the use of intramelanocytic cysteine for pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Evidence we searched of such a mechanism by comparing the influence of melanocytic Slc7a11 expression on pheomelanin?based pigmentation in developing Eurasian nuthatch Sitta europaea nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with Slc7a11 expression in the low?risk population as expected from the activity of this gene, but decreased with Slc7a11 expression in the high?risk population. The same was not observed in the expression of five other genes influencing pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of pheomelanin?based pigmentation also differed between populations, being positive in the low?risk population and negative in the high?risk population. The resulting pigmentation of birds was more intense in the high?risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for pheomelanin synthesis, which becomes independent of Slc7a11 expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress. informacion[at]ebd.csic.es: Galván & Sanz (2020) Differential influence of Slc7a11 expression and body condition on pheomelanin-based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk. J Avian Biol DOI 10.1111/jav.02275


https://onlinelibrary.wiley.com/doi/10.1111/jav.02275
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Brown bear attacks on humans: a worldwide perspective

Brown bear attacks on humans: a worldwide perspective

Negative encounters with brown bears are rare and mainly non-fatal. This is the main finding of this study where the authors investigated more than 600 brown bear attacks on humans in 2000-2015 across the range inhabited by the species. Defensive behavior of females protecting their cubs was documented in the majority of the attacks. Half of the attacked people were engaged in leisure activities in nature, such as hiking and berry or antler picking. Other frequent scenarios were the result of inappropriate and risk-enhancing human behaviors (e.g. walking in natural areas with an unleashed dog, or chasing a wounded bear while hunting), and could be reduced by improving public education and awareness of the issue. Bear attacks were more frequent in remote areas with low density of people and high density of bears. Authors highlight the importance of educating the large public about how to behave properly in bear country to increase both human and bear safety, as well as to promote coexistence. informacion[at]ebd.csic.es: Bombieri et al (2019) Brown bear attacks on humans: a worldwide perspective. Sci Rep https://doi.org/10.1038/s41598-019-44341-w


https://www.nature.com/articles/s41598-019-44341-w