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

C. Isaksson*, M. J. L. Magrath, T. G. G. Groothuis, J. Komdeur

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

10 Citations (Scopus)

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 languageEnglish
Pages (from-to)97-103
Number of pages7
JournalGeneral and Comparative Endocrinology
Volume165
Issue number1
DOIs
Publication statusPublished - 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

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