Adaptive sex differences in growth of pre-ovulation oocytes in a passerine bird

Alexander V. Badyaev, Hubert Schwabl, Rebecca L. Young, Renée A. Duckworth, Kristen J. Navara, A. F. Parlow

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


Maternal modification of offspring sex in birds has strong fitness consequences, however the mechanisms by which female birds can bias sex of their progeny in close concordance with the environment of breeding are not known. In recently established populations of house finches (Carpodacus mexicanus), breeding females lay a sex-biased sequence of eggs when ambient temperature causes early onset of incubation. We studied the mechanisms behind close association of incubation and sex-determination strategies in this species and discovered that pre-ovulation oocytes that produce males and females differed strongly in the temporal patterns of proliferation and growth. In turn, sex-specific exposure of oocytes to maternal secretion of prolactin and androgens produced distinct accumulation of maternal steroids in oocyte yolks in relation to oocyte proliferation order. These findings suggest that sex difference in oocyte growth and egg-laying sequence is an adaptive outcome of hormonal constraints imposed by the overlap of early incubation and oogenesis in this population, and that the close integration of maternal incubation, oocytes' sex-determination and growth might be under control of the same hormonal mechanism. We further document that population establishment and the evolution of these maternal strategies is facilitated by their strong effects on female and offspring fitness in a recently established part of the species range.

Original languageEnglish (US)
Pages (from-to)2165-2172
Number of pages8
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1577
StatePublished - Oct 22 2005


  • Constraints
  • Incubation
  • Maternal effects
  • Oogenesis
  • Sex ratio

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)


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