title: Free and esterified carotenoids in ornaments of an avian species: the relationship to color expression and sources of variability.
abstract: Many animal species show ornaments with yellow-orange-red colors produced by carotenoid pigments. Such traits have evolved as reliable signals of individual quality because of the costs inherent to their production or maintenance. In animal tissues, carotenoids are often found combined with free fatty acids, as carotenoid esters, which may confer more stability to coloration than free carotenoids. Surprisingly, the potential relevance of carotenoid esterification in the expression of animal sexual signals has been virtually ignored. Moreover, the sources of variability of esterified carotenoid levels are barely known, because most studies have not quantified their concentrations. Here, carotenoids in the ornaments (bill, eye rings, and legs) of red-legged partridges Alectoris rufa were quantified in their free and esterified forms. Carotenoid ester levels were the best predictors of leg color, whereas the redness of the other traits was better explained by free carotenoids. Nonetheless, total carotenoid levels (the sum of free and esterified forms) were always significantly correlated to redness. Young partridges had lower levels of free and esterified carotenids in the legs than did older individuals. Also, wild animals had higher ester levels and a higher proportion of carotenoids in esterified forms in all traits than did captive partridges. Probable physiological mechanisms explaining these patterns are discussed.
authors.affiliation: Instituto de Investigación en Recursos Cinegéticos, Consejo Superior de Investigaciones Cientificas, Universidad de Castilla-La Mancha, Junta de Comunidades de Castilla-La Mancha, Ronda de Toledo s/n, 13071 Ciudad Real, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: García-de Blas
authors.forename: Rafael
authors.initials: R
authors.lastname: Mateo
authors.forename: Javier
authors.initials: J
authors.lastname: Viñuela
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pérez-Rodríguez
authors.forename: Carlos
authors.initials: C
authors.lastname: Alonso-Alvarez
mesh_terms: D000375:Aging; D000822:Animal Husbandry; D000818:Animals; D000835:Animals, Wild; D001502:Beak / Q000502:physiology; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D046094:Galliformes / Q000502:physiology*; D006614:Hindlimb; D008297:Male; D010860:Pigments, Biological / Q000378:metabolism*; D012621:Seasons; D012879:Skin Physiological Phenomena
chemical_list: D010860:Pigments, Biological; D002338:Carotenoids