RESUMEN
Carotenoids are pigments responsible for the red, orange and yellow coloration of plants and animals. They may be beneficial in two ways; they have a powerful antioxidant activity, and they can behave as an immunostimulant. Animals however cannot synthesize carotenoids de novo, they must obtain them through their diet. In our experiments on Canaries, we investigated how mothers transfer their dietary carotenoid-related benefits to their offspring; either through the egg, or through the diet (during chicks' feeding). Female Canaries were allowed to access beta-carotene enriched food during egg formation and/or chicks' feeding. We sorted the chicks into four groups using the period when they assimilated the beta-carotene as a variable. The four groups were: (i) before hatching (from yolk), (ii) after hatching (from maternal feeding), (iii) before and after hatching, or (iv) never. Colorimetry and HPLC analysis from sub-samples of yolks confirmed the maternal transfer of dietary carotenoids to the yolk. Our results show that benefits from maternal dietary carotenoids are transferred to the chicks, but according to the period when they are assimilated by the chicks, the physiological effects are different. It was found that the chicks' growth was enhanced when carotenoids were assimilated both before and after hatching. However an increase in cellular immunity efficiency only occurs when the assimilation takes place after hatching.
Asunto(s)
Canarios/crecimiento & desarrollo , Proteínas del Huevo/metabolismo , Óvulo/metabolismo , beta Caroteno/metabolismo , Análisis de Varianza , Alimentación Animal , Animales , Animales Recién Nacidos , Canarios/metabolismo , Suplementos Dietéticos , Conducta Alimentaria , Femenino , Masculino , Conducta Materna , Pigmentación/fisiología , beta Caroteno/administración & dosificaciónRESUMEN
Early maternal effects in the form of substances accumulated in the egg, such as carotenoids and hormones, can be physiologically relevant for a good development of offspring. It has been found in different species that testosterone (T) can be beneficial to offspring by increasing growth rate, but detrimental by reducing immunocompetence and increasing oxidative stress. Carotenoids on the other hand are suggested to be beneficial because they can counteract the oxidative stress and the immune-depressive effect of T. In this study we analyzed the effect of prenatal T exposure in the grey partridge. We injected eggs with three doses of T (high, intermediate, and physiological). After hatching, chicks exposed to a prenatal high dose of T were fed with two diets (rich or poor) differing in beta-carotene content. We found a significant effect of T on both chick growth and cell-mediated immunity, with high T doses resulting in detrimental effects while low doses were beneficial. Detrimental effects of the high dose of T on immunity were mitigated by beta-carotene consumed in the diet. The differences between groups were observed in the early period of life (age 10 days for mass, and age 10 and 21 days for immunity), and disappeared in the following period, and up to 1 and 2 years later. Overall, our observations show that T in the egg is not detrimental but beneficial, and that negative effects are found only at supraphysiological concentrations. The negative effects of T on immunity could be balanced if chicks could consume a diet rich in beta-carotene.
Asunto(s)
Animales Recién Nacidos/fisiología , Aves/metabolismo , Yema de Huevo/química , Crecimiento/efectos de los fármacos , Inmunidad/efectos de los fármacos , Testosterona/farmacología , beta Caroteno/farmacología , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Peso Corporal/efectos de los fármacos , Dieta , Relación Dosis-Respuesta a Droga , Embrión no Mamífero , Inmunidad Celular/efectos de los fármacos , Testosterona/química , beta Caroteno/químicaRESUMEN
The challenge hypothesis predicts that plasma testosterone (T) concentration is high when male-male competitions are high and decreases when males are engaged in paternal care. In monogamous species, T concentration increases at the beginning of the breeding period and decreases after egg laying. According to the challenge hypothesis, increasing competition should also lead to T increase. The aim of our study was to test this hypothesis. In a first experiment, we measured the T profile of domesticated canaries housed with their mate in separated cages without competition. In a second one, we created a competition by housing male and female domestic canaries together (in an aviary) and emphasized this competition by limiting food access. We also studied social status effect. Our results showed no effect of social status in both sexes and no differences in female's T concentration. Concerning males, we obtained a clear monogamous T profile from the ones housed in a low competition situation and a polygamous profile from the others housed in high competition situation. Thus, our results support the hypothesis of the plasticity of the mechanisms controlling T concentration according to environmental conditions.
Asunto(s)
Canarios/fisiología , Conducta Competitiva/fisiología , Testosterona/sangre , Envejecimiento/fisiología , Animales , Femenino , Masculino , Conducta Social , Predominio Social , Medio SocialRESUMEN
The androgen concentration in birds' eggs varies with laying order, breeding conditions, and mate attractiveness. In passerine birds, mate attractiveness depends upon song quality. The aim of our study was to evaluate the effect of one criterion used by females to assess male song quality that is to say the presence of sexually attractive phrases on yolk androgen deposition. Twenty-five female Canaries were assigned to three experimental groups; in the first group, the females were allowed to hear songs made up with attractive phrases; in the second group, they were allowed to hear songs made up with non-attractive phrases; and in the control group, the females could not hear any song. Our results show that females allowed to hear songs with attractive phrases deposit significantly higher amounts of androgens (mostly testosterone) in their eggs than females without acoustical stimulation. The females exposed to songs with non-attractive phrases had androgen amounts halfway between the two other groups. This suggests that when females are paired with mates able to sing attractive phrases they can allocate more androgens in their eggs during the pre-laying period.
Asunto(s)
Andrógenos/metabolismo , Canarios/metabolismo , Yema de Huevo/metabolismo , Ovario/metabolismo , Conducta Sexual Animal/fisiología , Vocalización Animal/fisiología , Estimulación Acústica , Andrógenos/análisis , Animales , Yema de Huevo/química , Femenino , Masculino , Distribución Aleatoria , Reproducción/fisiologíaRESUMEN
We studied the mechanism of song production in the outbred common or domestic canary (Serinus canaria). The contribution that each side of the syrinx makes to song was investigated by observing the effect of unilaterally occluding the left or right primary bronchus, followed by section of the ipsilateral branch of the tracheosyringeal nerve. In other birds with a bilaterally intact vocal system we monitored airflow through each side of the syrinx, together with subsyringeal pressure, during spontaneous song. Song production by domestic canaries is not strongly lateralized as it is in the conspecific song-bred waterslager strain. Some syllables are produced entirely on the left or right side of the syrinx, whereas others contain sequential contributions from each side. Low fundamental frequencies are produced with the left syrinx and high frequencies by the right syrinx, increasing the frequency range of domestic canary song compared to that of the waterslager strain. Midrange frequencies can be generated by either side. Syllables at repetition rates below about 25 s(-1) were accompanied by minibreaths, which were usually bilateral. Unilateral minibreaths were typically on the left side. At higher syllable repetition rates, minibreaths were replaced by a respiratory pattern of pulsatile expiration. Our data show that strong unilateral dominance in song production, present in the waterslager strain, is not a trait of the species as a whole and that the pattern of song lateralization can be altered by selective breeding for particular song characteristics.