Birds' feather's colours are synthesised in their livers, not skins

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Washington, Apr 16 (ANI): Contrary to previous beliefs, the red carotenoids that provide the red colouration in the Common Crossbill is synthesised in the bird's liver and not its skin, according to a new study.

The findings revealed by Esther del Val, from the National History Museum in Barcelona, Spain, have implications for understanding the evolution of colour signalling in bird species.

Carotenoids have important physiological functions, including antioxidant, immunomodulating, and photoprotectant properties.

Many bird species use carotenoid pigments as colourants, which are responsible for most of their red, orange and yellow coloration.

Particularly, it has been shown that carotenoid-red colouration in birds act as an ornament, signalling the nutritional and health status of the individual and its ability to locate high quality resources.

In recent studies, scientists have suggested that the transformation of carotenoid pigments takes place directly in the follicles during feather growth.

However, the latest research has for the first time shown that contrary to previous assumptions, the liver acts as the main site for the synthesis of carotenoids responsible for the birds' coloration, not the skin.

The researchers examined the carotenoid content of the liver, blood, skin and feathers of seven common crossbills (finches) in which adult males display carotenoid-based coloration on the throat, breast and rump.

They were particularly interested in the anatomical origin of the birds' red plumage.

The primary red feather pigment of male crossbills was found in the birds' liver and blood, which implied that that the carotenoids are synthesized in the liver and then travel to the peripheral tissues via the bloodstream.

Del Val concluded: "This surprising divergence with previous studies raises the question whether there are inter-specific differences in anatomical sites for conversion of carotenoids. Understanding inter-specific variation in mechanisms of colour production may be the key to comprehend the different evolutionary pathways involved in colour signalling."

The study has been published online in Springer's journal Naturwissenschaften. (ANI)

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