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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] 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
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Sexual dichromatism and condition-dependence in the skin of a bat

Sexual dichromatism and condition-dependence in the skin of a bat

Bats are assumed not to use vision for communication, despite recent evidence of their capacity for color vision. The possibility that bats use color traits as signals has thus been overlooked. Some tent-roosting bats have a potential for visual signaling because they exhibit bright yellow skin, a trait that in birds often acts as a sexual signal. The authors searched for evidence of sexual dichromatism in the yellow bare skin of Honduran white bats Ectophylla alba, the first reported mammal with a capacity to deposit significant amounts of carotenoid pigments in the skin. Skin yellow chroma, a measure that reflects carotenoid content, increases in the ears and nose-leaf during development probably due to an increase in dietary carotenoid accumulation. Once in the adulthood, the yellow color of the nose-leaf becomes brighter in males, representing the first evidence of sexual dichromatism in a bat. The nose-leaf brightness tends to covary positively with the body condition of males. It was also found that the skin shows a reflectance peak at 530 nm that virtually coincides with the main reflectance peak (540 nm) of the back side of Heliconia leaves used as roosts. This suggests that these leaves were selected because of camouflage benefits, and the rich lighting conditions of these roosting places then favored the use of skin coloration as a sexual signal. These findings open a new perspective in the physiological and behavioral ecology of bats in which vision has a more relevant role than previously thought. informacion[at] Rodríguez-Herrera et al (2019) Sexual dichromatism and condition-dependence in the skin of a bat. J Mammal