Windows of embryonic sexual lability in two lizard species with environmental sex determination

Richard Shine*, Daniel A. Warner, Rajkumar Radder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)
27 Downloads (Pure)


Temperature-dependent sex determination (TSD) occurs in all major reptile lineages, but the selective forces and physiological mechanisms that link sex to incubation temperature may differ among and within those groups. Different models for TSD evolution make different predictions about when offspring sex will respond to environmental cues. Although TSD has evolved in several lizard lineages, there is less detailed information on these taxa than in turtles and crocodilians with TSD. We incubated eggs of an agamid lizard (Amphibolurus muricatus) and a scincid lizard (Bassiana duperreyi), two species with TSD. Rather than manipulate incubation temperature to identify periods of sexual lability (as in most previous studies of this topic), we topically applied the aromatase inhibitor fadrozole to eggs at a variety of times through the incubation period. Fadrozole application sex-reversed the resultant hatchlings if applied from the time of oviposition until at least 60% of the way through incubation. In all of the TSD lizard species studied so far, offspring sex is determined either while the eggs are held inside the mother's body or soon after oviposition, providing substantial maternal control over incubation temperatures at this critical period. Hence, the hypothesis that TSD evolves because it enables offspring sex to be matched to conditions that are unpredictable at the time of laying is less likely to apply to squamates than to turtles, sphenodontians, and (especially) crocodiles, in which the period of sexual lability is delayed until long after oviposition.

Original languageEnglish
Pages (from-to)1781-1788
Number of pages8
Issue number7
Publication statusPublished - Jul 2007
Externally publishedYes

Bibliographical note

Copyright 2007 by the Ecological Society of America. Originally published in Shine, R., Warner, D. A., & Radder, R. (2007). Windows of embryonic sexual lability in two lizard species with environmental sex determination. Ecology, 88(7), 1781-1788.


  • Agamidae
  • Amphibolurus muricatus
  • aromatase inhibitor
  • Bassiana duperreyi
  • embryonic development
  • fadrozole
  • incubation
  • jacky dragon
  • Scincidae
  • temperature-dependent sex determination
  • thermosensitive period


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