BARCELONA, Spain, April 15 (UPI) -- Spanish-led scientists say they've determined the red coloring of some bird feathers originates in the liver, not in the birds' skin.
Researchers led by Esther del Val of the National History Museum in Barcelona, Spain, discovered red carotenoids that give the common crossbill (Loxia curvirostra) its red coloration are produced in the liver, contrary to previous assumptions. They said their finding has implications for understanding the evolution of color signaling in bird species.
The researchers said they 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 their throat, breast and rump. The scientists found the primary red feather pigment of male crossbills in the birds' liver and blood, implying carotenoids are synthesized in the liver and then travel to the peripheral tissues via the bloodstream.
"This surprising divergence with previous studies raises the question whether there are inter-specific differences in anatomical sites for conversion of carotenoids," said del Val. "Understanding inter-specific variation in mechanisms of color production may be the key to comprehend the different evolutionary pathways involved in color signaling."
The study appears in the journal Naturwissenschaften.
