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Biomedical subjects

D Rubolini

Publications and source records attributed to D Rubolini.

5 recordsLinked to original sources
PubMed2006

Increased egg estradiol concentration feminizes digit ratios of male pheasants (Phasianus colchicus).

The length ratio between individual digits differs between males and females in humans, other mammals, lizards, and one bird species. Sexual dimorphism in digit ratios and variation among individuals of the same sex may depend on differential exposure to androgens and estrogens during embryonic life. Organizational effects of sex hormones could cause the observed correlations between digit ratios and diverse phenotypic traits in humans. However, no study has investigated experimentally the effect of prenatal estrogens on digit ratios. We analyzed the effect of estradiol injection in ring-necked pheasant (Phasianus colchicus) eggs on digit ratios. Males from control eggs had higher ratios between the second or third and the fourth digit of the right foot compared to females. Estradiol-treated eggs produced males with lower (feminized) right foot second to fourth digit ratio. Thus, we provided the first experimental evidence that prenatal exposure to physiologically high estrogen levels affects bird digit ratios.

Animals↗
PubMed2006

Early maternal, genetic and environmental components of antioxidant protection, morphology and immunity of yellow-legged gull (Larus michahellis) chicks.

Maternal effects mediated by egg quality are important sources of offspring phenotypic variation and can influence the course of evolutionary processes. Mothers allocate to the eggs diverse antioxidants that protect the embryo from oxidative stress. In the yellow-legged gull (Larus michahellis), yolk antioxidant capacity varied markedly among clutches and declined considerably with egg laying date. Analysis of bioptic yolk samples from clutches that were subsequently partially cross-fostered revealed a positive effect of yolk antioxidant capacity on embryonic development and chick growth, but not on immunity and begging behaviour, while controlling for parentage and common environment effects. Chick plasma antioxidant capacity varied according to rearing environment, after statistically partitioning out maternal influences mediated by egg quality. Thus, the results of this study indicate that egg antioxidants are important mediators of maternal effects also in wild bird populations, especially during the critical early post-hatching phase.

Animals↗
PubMed2003

Colour polymorphism in birds: causes and functions.

We studied polymorphism in all species of birds that are presently known to show intraspecific variation in plumage colour. At least three main mechanisms have been put forward to explain the maintenance of polymorphism: apostatic, disruptive and sexual selection. All of them make partly different predictions. Our aims were to investigate evolutionary causes and adaptive functions of colour polymorphism by taking into account a number of ecological and morphological features of polymorphic species. Overall, we found 334 species showing colour polymorphism, which is 3.5% of all bird species. The occurrence of colour polymorphism was very high in Strigiformes, Ciconiiformes, Cuculiformes and Galliformes. Phylogenetically corrected analysis using independent contrasts revealed that colour polymorphism was maximally expressed in species showing a daily activity rhythm extended to day/night, living in both open and closed habitats. All these findings support the hypothesis that colour polymorphism probably evolved under selective pressures linked to bird detectability as affected by variable light conditions during activity period. Thus, we conclude that selective agents may be prey, predators and competitors, and that colour polymorphism in birds may be maintained by disruptive selection.

Adaptation, Physiological↗
PubMed2003

Humoral immune response in relation to senescence, sex and sexual ornamentation in the barn swallow (Hirundo rustica).

Performance of animals may decline with age. The effects of senescence, however, may differ between the sexes because of differences in physiology and behaviour. Acquired immunity provides hosts with efficient mechanisms of anti-parasite defence, but the effect of senescence on immunocompetence has never been studied in natural populations. In the barn swallow (Hirundo rustica), primary antibody response to an antigen during one breeding season declined with age in females, while secondary response during the following breeding season declined with age in both sexes. Parasite-mediated sexual selection theory posits that male secondary sexual characters reveal resistance to parasites. Males with large tail ornaments had stronger primary response, retained larger antibody levels until the following year, but did not differ in secondary response compared with short-tailed males, as predicted if ornamentation reflects resistance to parasites. This is the first study showing that immunocompetence declines with age in any vertebrate under natural conditions.

Aging↗