Suchergebnisse

Avian embryos are exposed to yolk androgens that are incorporated into the egg by the ovulating female. These steroids can affect several aspects of embryo development, often resulting in increases in overall size or the speed of growth of different traits. However, several studies suggest that they also entail immune costs to the offspring. In this study, we explored whether variation in yolk androgen concentration affected several measures of the constitutive and cell-mediated immune axes in the spotless starling (Sturnus unicolor). Using a within-brood design, we injected different doses of androgens (testosterone and androstenedione) into the eggs. Our study showed that experimentally increased yolk androgens led to sex-specific immunosuppression in both the innate and adaptive axes of the immune system. Both cell-mediated immune response (CMI) and lysozyme activity decreased with increasing androgen levels injected into the egg in the case of male nestlings, whereas there were no effects on females. The effects that we found were always linear: no quadratic or threshold patterns were detected. We found no effects of the experimental treatment in hemolysis or agglutination capacity, but these measures were negatively correlated with CMI, suggesting negative correlation among different branches of the immune system. Blood (trypanosomes and hemosporidians) and intestinal (coccidia) parasites were not affected by the experimental increase of yolk androgen levels. Our results show that in our study species yolk androgens induce immunosuppression in some axes of the male nestling immune system. Further studies should analyze the proximate causes for these contrasting effects in different axes of the immune system and the reason for the differential impact on males and females. ; This study was financed by project grants CGL2008–03501 and CGL2011–26318 to D.G. (Ministerio de Ciencia e Innovación [MICINN]). J.M. was supported by an FPI (Formación de Personal Investigador) grant (BES-2009–021383) from MICINN. L.P.-R. was supported by a postdoctoral grant from MICINN through the Juan de la Cierva Subprogram (JCI-2008–2059), followed by a postdoctoral contract from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Program for Centres of Excellence in Research, Development, and Innovation (SEV-2012–0262). M.E.O.-S. was supported by a postdoctoral grant from MICINN through the Juan de la Cierva Subprogram (JCI-2009–03865), followed by a Marie Curie Intra-European Fellowship of the European Union's 7th Framework Program (2012–328328). ; Peer reviewed

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. ; Esther García-de Blas was supported by a predoctoral grant (JAE-PRE program) from the Consejo Superior de Investigaciones Científicas cofinanced by Fondo Socia Europeo. Lorenzo Pérez-Rodríguez was supported by a "Juan de la Cierva" postdoctoral contract from the Spanish Ministerio de Ciencia e Innovación (JCI-2008-2059). This study was funded by Consejería de Educación y Ciencia, Junta de Comunidades de Castilla la Mancha (PII1I09-0271-5037), and Ministerio de Economía y Competitividad (CGL2009-10883-C02-02) from the Spanish government. ; Peer reviewed