Scientists have just pinpointed the gene that allows birds to produce the color red in their beaks and retinas. Further, their findings lend insight into why birds of this color are a favorite romantic prospect.
Nick Mundy from University of Cambridge and his colleagues determined a group of three genes detected in wild zebra finches with red beaks but which was neither found nor detected in the genetic region of their yellow-beaked captive counterparts.
One gene in particular stood out among more than 15,000 genetic variations potentially linked with red coloring: CYP2J19, which is active in the birds' skin and liver and a thousand times more active in red birds than yellow ones.
Red And Mating Success
The bird kingdom seems to put a premium on the color red; in many species, the redder the male, the more successful it is at finding mates. The color is also often used to deter rival birds.
“[N]obody knows for sure why red color is associated with reproductive success,” said senior author Joseph Carbo of Washington University. “We thought that if we could figure out how they produced that red color, that would help us understand the advantage to being red.”
The researchers appeared to find an answer: the identified genes are known to play an important role in detoxification – something revealing whether a bird can rid of hazardous substances in the body and therefore indicating its quality as a potential mate.
"In sexual selection, red color is thought to signal individual quality and one way it can do this is if the type or amount of pigmentation is related to other physiological processes, like detoxification," explained study author Staffan Andersson from the University of Gothenburg.
Gene Evolution From The Retina To Skin
One or more of these “redness” genes have also been found active in the eye’s retina. Birds maintain a range of pigments in the photoreceptor cells of their retinas, allowing them to see many more colors than mammals.
Red eye pigments were detected across bird species, even in those without a reddish shade in their bodies. However, only red-feathered birds express the genes in their skin, suggesting that the means to manufacture this gene may have evolved in the skin in addition to the retina.
The study was published May 19 in the journal Current Biology.
Photo: Jaroslav Dvorský | Flickr
