Androgens during development in a bird species with extremely sexually dimorphic growth, the brown songlark, Cinclorhamphus cruralis

Abstract In birds, early exposure to androgens has been shown to influence offspring growth and begging behaviour, and has been proposed as a mechanism for the development of sexual size dimorphism (SSD). Sex specific effects during development can occur due to sex-specific allocation of maternal an...

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Bibliographic Details
Published in:General and comparative endocrinology 2010-01, Vol.165 (1), p.97-103
Main Authors: Isaksson, C, Magrath, M.J.L, Groothuis, T.G.G, Komdeur, J
Format: Article
Language:English
Subjects:
Animals
Differential allocation
Endocrinology & Metabolism
Female
Gene Expression Regulation, Developmental
Male
Maternal effects
Passeriformes - growth & development
Passeriformes - metabolism
Passeriformes - physiology
Radioimmunoassay
Sex Characteristics
Sex Ratio
Sexual size dimorphism
Testosterone
Testosterone - metabolism
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Summary:Abstract In birds, early exposure to androgens has been shown to influence offspring growth and begging behaviour, and has been proposed as a mechanism for the development of sexual size dimorphism (SSD). Sex specific effects during development can occur due to sex-specific allocation of maternal androgens, sensitivity to, or synthesis of, androgens. In addition, maternal hormones have been suggested as a mechanism to skew brood sex ratio. This study uses one of the world’s most extreme SSD species, the brown songlark Cinclorhamphus cruralis, to investigate (1) sex-specific differences of androgens in yolk and chick plasma and (2) the relationship between androgens and sex ratio bias. The study reveals no indication of sex-specific maternal allocation, but a modest sex effect during the later stages of incubation when the embryo starts to produce its own androgens. Moreover, there was a strong seasonal sex ratio bias: female-biased early and male-biased later in the season, but yolk testosterone (T) did not show a seasonal trend. Taken together these results suggest that if androgens, from any source, have a significant role in development of SSD in this species it is most likely via sex-specific sensitivity or synthesis rather than differential maternal transfer to the egg.
ISSN:0016-6480
1095-6840
DOI:10.1016/j.ygcen.2009.06.015