Effects of elevated yolk testosterone levels on survival, growth and immunity of male and female yellow-legged gull chicks |
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Authors: | Diego Rubolini Maria Romano Roberta Martinelli Nicola Saino |
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Institution: | (1) Dipartimento di Biologia Animale, Università degli Studi di Pavia, P.zza Botta 9, 27100 Pavia, Italy;(2) Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, 20133 Milan, Italy |
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Abstract: | Androgen hormones of maternal origin contained in the eggs of avian species are considered to have positive effects on offspring
characteristics and performance. However, negative consequences have also been reported, suggesting that mothers may experience
a trade-off between beneficial and detrimental effects of egg androgens to offspring fitness. We studied the effects of elevated
yolk testosterone (T) concentration on survival, development and phenotype of male and female yellow-legged gull (Larus michahellis) chicks by injecting egg yolks with physiological doses of the hormone. Elevated yolk T resulted in a male-biased post-hatching
sex ratio, T-treated clutches producing a greater proportion of males compared to control ones at day 4 post-hatching, likely
resulting from a reduction of female embryonic survival, whereas no effect of hormone treatment on hatching success or short-term
chick survival was observed. In addition, T depressed post-hatching body mass in both sexes but had no effects on the intensity
of the cell-mediated immune response or skeletal growth. No sex differences in egg characteristics or chick phenotype were
detected. Time to hatching was not affected by T, but females originating from first laid eggs hatched earlier than males
of the same laying order, independently of hormone treatment. However, the implications of sex differences in hatching times
are unclear in the study species. Taken together, our results suggest that female yellow-legged gulls may be constrained in
transferring androgens to their eggs by negative consequences on the viability of female offspring and growth of chicks of
the two sexes. |
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Keywords: | Embryo sex Maternal effects Phenotypic engineering T-cell-mediated immunity Yolk androgens |
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