The liver but not the skin is the site for conversion of a red carotenoid in a passerine bird.
Carotenoids may provide numerous health benefits and are also responsible for the integumentary coloration of many bird species. Despite their importance, many aspects of their metabolism are still poorly known, and even basic issues such as the anatomical sites of conversion remain controversial. Recent studies suggest that the transformation of carotenoid pigments takes place directly in the follicles during feather growth, even though the liver has been previously recognised as a storing organ for these pigments with a certain potential for conversion. In this context, we analysed the carotenoid profile of plasma, liver, skin and feathers of male Common Crossbills (Loxia curvirostra). Interestingly, the derivative feather pigment 3-hydroxy-echinenone was detected in the liver and in the bloodstream (i.e. the necessary vehicle to transport metabolites to colorful peripheral tissues). Our results demonstrate for the first time with empirical data that the liver may act as the main site for the synthesis of integumentary carotenoids. This finding contradicts previous assumptions and raises the question of possible inter-specific differences in the site of carotenoid conversion in birds.
Behavioural & Evolutionary Ecology Associate Research Unit (CSIC), Natural History Museum, Passeig Picasso s/n, 08003, Barcelona, Spain. estherdelval@yahoo.es
Esther
E
del Val
Juan Carlos
JC
Senar
Juan
J
Garrido-Fernández
Manuel
M
Jarén
Antoni
A
Borràs
Josep
J
Cabrera
Juan José
JJ
Negro
D000375:Aging / Q000378:metabolism; D000818:Animals; D002338:Carotenoids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005241:Feathers / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D046109:Passeriformes / Q000254:growth & development / Q000378:metabolism*; D010858:Pigmentation / Q000502:physiology*; D012867:Skin / Q000378:metabolism*
D002338:Carotenoids