Skip to main content
PMC home page
Proceedings of the Royal Society B: Biological Sciences logoLink to Proceedings of the Royal Society B: Biological Sciences
. 2000 Sep 7;267(1454):1745–1749. doi: 10.1098/rspb.2000.1205

Environmental sex determination in a reptile varies seasonally and with yolk hormones.

R M Bowden 1, M A Ewert 1, C E Nelson 1
PMCID: PMC1690737  PMID: 12233772

Abstract

Most hypotheses that have been put forward in order to explain the persistence of environmental sex determination (ESD) in reptiles assume a relatively fixed association of sex with temperature-induced phenotype and no maternal influence on offspring sex. Here we demonstrate the association of maternally derived yolk hormone levels with the offspring sex ratio and describe two new aspects of temperature-dependent sex determination (TSD), i.e. seasonal variation in both thermal response and yolk steroid levels. Eggs from painted turtles (Chrysemys picta) were incubated at 28 degrees C. The hatchling sex ratio at 28 degrees C (i.e. the phenotypic reaction norm for sex at 28 degrees C) shifted seasonally from ca. 72% male to ca. 76% female. Yolk oestradiol (E2) increased seasonally while testosterone (T) decreased. The proportion of males in a clutch decreased as E2 levels increased and the E2:T ratio increased. These new findings are discussed in relation to heritability and adaptive explanations for the persistence of ESD in reptiles. Maternally derived yolk hormones may provide a mechanism for the seasonal shift in the sex ratio which in turn may help explain the persistence of ESD in reptiles. They may also explain those clutches of other reptiles with TSD that fail to yield only males at maximally masculinizing conditions.

Full Text

The Full Text of this article is available as a PDF (212.7 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bogart M. H. Sex determination: a hypothesis based on steroid ratios. J Theor Biol. 1987 Oct 7;128(3):349–357. doi: 10.1016/s0022-5193(87)80077-2. [DOI] [PubMed] [Google Scholar]
  2. Bull J. J., Bulmer M. G. Longevity enhances selection of environmental sex determination. Heredity (Edinb) 1989 Dec;63(Pt 3):315–320. doi: 10.1038/hdy.1989.104. [DOI] [PubMed] [Google Scholar]
  3. Bull J. J., Vogt R. C. Temperature-dependent sex determination in turtles. Science. 1979 Dec 7;206(4423):1186–1188. doi: 10.1126/science.505003. [DOI] [PubMed] [Google Scholar]
  4. Callard I. P., Lance V., Salhanick A. R., Barad D. The annual ovarian cycle of Chrysemys picta: correlated changes in plasma steroids and parameters of vitellogenesis. Gen Comp Endocrinol. 1978 Jul;35(3):245–257. doi: 10.1016/0016-6480(78)90069-2. [DOI] [PubMed] [Google Scholar]
  5. Charnov E. L., Bull J. When is sex environmentally determined? Nature. 1977 Apr 28;266(5605):828–830. doi: 10.1038/266828a0. [DOI] [PubMed] [Google Scholar]
  6. Conley A. J., Elf P., Corbin C. J., Dubowsky S., Fivizzani A., Lang J. W. Yolk steroids decline during sexual differentiation in the alligator. Gen Comp Endocrinol. 1997 Aug;107(2):191–200. doi: 10.1006/gcen.1997.6913. [DOI] [PubMed] [Google Scholar]
  7. Crews D., Bull J. J., Wibbels T. Estrogen and sex reversal in turtles: a dose-dependent phenomenon. Gen Comp Endocrinol. 1991 Mar;81(3):357–364. doi: 10.1016/0016-6480(91)90162-y. [DOI] [PubMed] [Google Scholar]
  8. Crews D., Cantú A. R., Rhen T., Vohra R. The relative effectiveness of estrone, estradiol-17 beta, and estriol in sex reversal in the red-eared slider (Trachemys scripta), a turtle with temperature-dependent sex determination. Gen Comp Endocrinol. 1996 Jun;102(3):317–326. doi: 10.1006/gcen.1996.0075. [DOI] [PubMed] [Google Scholar]
  9. Crews D. Temperature-dependent sex determination: the interplay of steroid hormones and temperature. Zoolog Sci. 1996 Feb;13(1):1–13. doi: 10.2108/zsj.13.1. [DOI] [PubMed] [Google Scholar]
  10. Janzen F. J. Heritable variation for sex ratio under environmental sex determination in the common snapping turtle (Chelydra serpentina). Genetics. 1992 May;131(1):155–161. doi: 10.1093/genetics/131.1.155. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Janzen F. J., Wilson M. E., Tucker J. K., Ford S. P. Endogenous yolk steroid hormones in turtles with different sex-determining mechanisms. Gen Comp Endocrinol. 1998 Sep;111(3):306–317. doi: 10.1006/gcen.1998.7115. [DOI] [PubMed] [Google Scholar]
  12. Schwabl H. Yolk is a source of maternal testosterone for developing birds. Proc Natl Acad Sci U S A. 1993 Dec 15;90(24):11446–11450. doi: 10.1073/pnas.90.24.11446. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Sheehan D. M., Willingham E., Gaylor D., Bergeron J. M., Crews D. No threshold dose for estradiol-induced sex reversal of turtle embryos: how little is too much? Environ Health Perspect. 1999 Feb;107(2):155–159. doi: 10.1289/ehp.99107155. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Shine R. Why is sex determined by nest temperature in many reptiles? Trends Ecol Evol. 1999 May;14(5):186–189. doi: 10.1016/s0169-5347(98)01575-4. [DOI] [PubMed] [Google Scholar]
  15. Wibbels T., Bull J. J., Crews D. Synergism between temperature and estradiol: a common pathway in turtle sex determination? J Exp Zool. 1991 Oct;260(1):130–134. doi: 10.1002/jez.1402600117. [DOI] [PubMed] [Google Scholar]
  16. Wingfield J. C., Farner D. S. The determination of five steroids in avian plasma by radioimmunoassay and competitive protein-binding. Steroids. 1975 Sep;26(3):311–321. doi: 10.1016/0039-128x(75)90077-x. [DOI] [PubMed] [Google Scholar]

Articles from Proceedings of the Royal Society B: Biological Sciences are provided here courtesy of The Royal Society

RESOURCES