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. (C) 2009 Elsevier Inc. All rights reserved.
Original language | English |
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Pages (from-to) | 97-103 |
Number of pages | 7 |
Journal | General and Comparative Endocrinology |
Volume | 165 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1-Jan-2010 |
Keywords
- Testosterone
- Sexual size dimorphism
- Differential allocation
- Maternal effects
- Sex ratio
- PRIMARY SEX-RATIO
- BLACK-HEADED GULL
- YOLK TESTOSTERONE
- ZEBRA FINCHES
- SIZE DIMORPHISM
- MATERNAL TESTOSTERONE
- GALLUS-DOMESTICUS
- STEROID-LEVELS
- LAYING ORDER
- AVIAN EGGS