Richard Crossley [creativecommons license] via Wikimedia CommonsPheomelanin, a pigment responsible for reddish and chestnut coloration, is found only in higher vertebrates (i.e., birds and mammals) and carries several physiological costs. Its presence is associated with greater risks of skin cell damage and melanoma, and its synthesis in the body uses up the beneficial antioxidant glutathione. Pheomelanin is also phototoxic, producing reactive oxygen species when exposed to ultraviolet radiation. Given these costs, Ismael Galván and Anders P. Møller (Université Paris-Sud, France) asked whether there are any benefits to pheomelanin that could explain its development and persistence in vertebrates.
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