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Naturwissenschaften

, Volume 94, Issue 3, pp 207–212 | Cite as

Increased egg estradiol concentration feminizes digit ratios of male pheasants (Phasianus colchicus)

  • N. Saino
  • D. Rubolini
  • M. Romano
  • G. Boncoraglio
Original Article

Abstract

The length ratio between individual digits differs between males and females in humans, other mammals, lizards, and one bird species. Sexual dimorphism in digit ratios and variation among individuals of the same sex may depend on differential exposure to androgens and estrogens during embryonic life. Organizational effects of sex hormones could cause the observed correlations between digit ratios and diverse phenotypic traits in humans. However, no study has investigated experimentally the effect of prenatal estrogens on digit ratios. We analyzed the effect of estradiol injection in ring-necked pheasant (Phasianus colchicus) eggs on digit ratios. Males from control eggs had higher ratios between the second or third and the fourth digit of the right foot compared to females. Estradiol-treated eggs produced males with lower (feminized) right foot second to fourth digit ratio. Thus, we provided the first experimental evidence that prenatal exposure to physiologically high estrogen levels affects bird digit ratios.

Keywords

2D:4D Birds Estrogen Feminization 

Notes

Acknowledgment

We thank all the people who helped during experimental work, A. Formenti for drawing the pheasant foot, and the referees for constructive criticism.

References

  1. Adkins EK (1979) Effect of embryonic treatment with estradiol or testosterone on sexual differentiation of the quail brain: critical period and dose–response relationships. Neuroendocrinology 29:178–185PubMedGoogle Scholar
  2. Balthazart J, Adkins-Regan E (2002) Sexual differentiation of brain and behavior in birds. In: Pfaff DW, Arnold AP, Etgen AM, Fahrbach SE, Rubin RT (eds) Hormones, brain and behavior, vol 4. Elsevier, Amsterdam, pp 223–301Google Scholar
  3. Baratti M, Alberti A, Groenen M, Veenendaal T, Dessì-Fulgheri F (2001) Polymorphic microsatellites developed by cross-species amplifications in common pheasant breeds. Anim Genet 32:222–225PubMedCrossRefGoogle Scholar
  4. Brown WM, Finn CJ, Breedlove SM (2002a) Sexual dimorphism in digit–length ratios of laboratory mice. Anat Rec 267:231–234PubMedCrossRefGoogle Scholar
  5. Brown WM, Hines M, Fane BA, Breedlove SM (2002b) Masculinized finger length patterns in human males and females with congenital adrenal hyperplasia. Horm Behav 42:380–386PubMedCrossRefGoogle Scholar
  6. Buck JJ, Williams RM, Huges IA, Acerini CL (2003) In-utero androgen exposure and 2nd to 4th digit length ratio—comparison between healthy controls and females with classical congenital adrenal hyperplasia. Hum Reprod 18:976–979PubMedCrossRefGoogle Scholar
  7. Burley NT, Foster VS (2004) Digit ratio varies with sex, egg order and strength of mate preference in zebra finches. Proc R Soc Lond B 271:239–244CrossRefGoogle Scholar
  8. Cramp S (1998) The birds of the Western Palearctic, CD-ROM edition. Oxford University Press, OxfordGoogle Scholar
  9. Forstmeier W (2005) Quantitative genetics and behavioural correlates of digit ratio in the zebra finch. Proc R Soc Lond B 272:2641–2649CrossRefGoogle Scholar
  10. Kimball RT, Ligon JD (1999) Evolution of avian plumage dichromatism from a proximate perspective. Am Nat 154:182–193CrossRefGoogle Scholar
  11. Leoni B, Canova L, Saino N (2005) Sexual dimorphism in metapodial and phalanges length ratios in the wood mouse. Anat Rec 286A:955–961CrossRefGoogle Scholar
  12. Lutchmaya S, Baron-Cohen S, Raggatt P, Knickmeyer R, Manning JT (2004) 2nd to 4th digit ratios, fetal testosterone and estradiol. Early Hum Dev 77:23–28PubMedCrossRefGoogle Scholar
  13. Manning JT (2002) Digit ratios. Rutgers University Press, New BrunswickGoogle Scholar
  14. Manning JT, Scutt D, Wilson J, Lewis-Jones DJ (1998) The ratio of 2nd to 4th digit length: a predictor of sperm number and levels of testosterone, LH and oestrogen. Hum Reprod 13:3000–3004PubMedCrossRefGoogle Scholar
  15. Manning JT, Callow M, Bundred PE (2003) Finger and toes ratios in humans and mices: implications for the aetiology of deseases influenced by Hox genes. Med Hypotheses 60:340–343PubMedCrossRefGoogle Scholar
  16. McFadden D, Shubel E (2002) Relative lengths of finger and toes in human males and females. Horm Behav 42:492–500PubMedCrossRefGoogle Scholar
  17. Nakagawa S (2004) A farewell to Bonferroni: the problems of low statistical power and publication bias. Behav Ecol 15:1044–1045CrossRefGoogle Scholar
  18. Okten A, Kalyoncu M, Yaris N (2002) The ratio of second- and fourth-digit lenghts and congenital hyperplasia due to 21-hydroxylase deficiency. Early Hum Dev 70:47–54PubMedCrossRefGoogle Scholar
  19. Peters M, Mackenzie K, Bryden P (2002) Finger length and distal finger extent patterns in human. Am J Phys Anthropol 117:209–217PubMedCrossRefGoogle Scholar
  20. Putz DA, Gaulin SJC, Sporter RJ, McBurney DH (2004) Sex hormones and finger length. What does 2D:4D indicate? Evol Hum Behav 25:182–199CrossRefGoogle Scholar
  21. Romano M, Rubolini D, Martinelli R, Bonisoli Alquati A, Saino N (2005) Experimental manipulation of yolk testosterone affects digit length ratios in the ring-necked pheasant (Phasianus colchicus). Horm Behav 48:342–346PubMedCrossRefGoogle Scholar
  22. Romer AS (1955) The vertebrate body. Saunders, PhiladelphiaGoogle Scholar
  23. Roney JR, Whitham JC, Leoni M, Bellem A, Wielebnowski N, Maestripieri D (2004) Relative digit lengths and testosterone levels in Guinea baboons. Horm Behav 45:285–290PubMedCrossRefGoogle Scholar
  24. Rubolini D, Pupin F, Sacchi R, Gentilli A, Zuffi MAL, Galeotti P, Saino N (2006) Sexual dimorphism in digit length ratios in two lizard species. Anat Rec 288A:491–497CrossRefGoogle Scholar
  25. Schumacher M, Hendrick JC, Balthazart J (1989) Sexual differentiation in quail: critical period and hormonal specificity. Horm Behav 23:130–149PubMedCrossRefGoogle Scholar
  26. Uitenbroek DG (1997) SISA—Bonferroni <http://home.clara.net/sisa/bonfer.htm>
  27. van Anders SM, Vernon PA, Wilbur CJ (2006) Finger-length ratios show evidence of prenatal hormone-transfer between opposite-sex twins. Horm Behav 49:315–319PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • N. Saino
    • 1
  • D. Rubolini
    • 2
  • M. Romano
    • 1
  • G. Boncoraglio
    • 1
  1. 1.Dipartimento di BiologiaUniversità degli Studi di MilanoMilanItaly
  2. 2.Dipartimento di Biologia AnimaleUniversità degli Studi di PaviaPaviaItaly

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