Sexual dimorphism in digit length ratios of the second to fourth digits (2D:4D) in two species of green toads (Pelobates syriacus Boettger, 1889 and Bufo viridis (Laurenti, 1768))

Alinezhadi, Iman; Heidari, Nastaran; Javanbakht, Hossein

doi:10.52547/nbr.7.3.295

Sexual dimorphism in digit length ratios of the second to fourth digits (2D:4D) in two species of green toads (Pelobates syriacus Boettger, 1889 and Bufo viridis (Laurenti, 1768))

Authors

Iman Alinezhadi ¹

Nastaran Heidari ²

Hossein Javanbakht ¹

¹ University of Guilan

² Kharazmi University

https://doi.org/10.52547/nbr.7.3.295

Abstract

Sexual dimorphism in the ratio of digits length is a morphological feature resulted from the interaction between sex hormones and prenatal Hox genes, the latter is known to control the development of both limbs and genitals. The status of this trend and ratios have been investigated in various animal groups, including humans, other mammals, birds, reptiles, and amphibians. In this study, the body length and sexual dimorphism in the second-to-fourth, second-to-third and third-to-fourth digit lengths ratios (i.e., 2D:3D, 2D:4D, 3D:4D) of left fore and hind limbs were investigated in 54 specimens of toads collected from the northern Iran, including Bufo viridis (16 males and 19 females) and Pelobates syriacus (10 males and 9 females). In addition, the body length of the studied specimens were recorded. The results showed that the average body length (SVL) of female individuals of Pelobates syriacus was higher than those in males, which was found to be statistically significant (P≤0.05). Meanwhile, the average body length (SVL) of female individuals of Bufo viridis was found to be higher than those in males, however, the difference was not statistically significant. No sexual dimorphism was detected in the second-to-fourth, second-to-third and third-to-fourth digit lengths ratios of left fore and hind limbs between the male and female undividuals of Bufo viridis. However, the second-to-fourth digit ratio (2D:4D) in Pelobates syriacus species were found to be significantly different (P=0.040) between the male and female individuals, as the ratio was higher in males than females. Therefore, it could be concluded that the sexual dimorphism in 2D:4D of Pelobates syriacus species is consistent with those in most amphibians and diapsids.

Keywords

Amphibia

Development

Hox gene

morphology

vertebrates

20.1001.1.24236330.1399.7.3.12.8

Badyaev, A. 2002. Growing apart: an ontogenetic perspective on the evolution of sexual size dimorphism. Trends in Ecology & Evolution 17: 369-378.
Bailey, A. & Hurd, L. 2005. Finger length ratio (2D:4D) correlates with physical aggression in men but not in women. Biological Psychology 68: 215-222.
Bailey, A., Wahlsten, D. & Hurd, P. 2005. Digit ratio (2D:4D) and behavioral differences between inbred mouse strains. Genes Brain and Behavior 4: 318-323.
Brown, W.M., Finn, C.J. & Breedlove, S. 2002a. Sexual dimorphism in digit-length ratios of laboratory mice. The Anatomical Record 267: 231-234.
Brown, W.M., Finn, C.J., Cooke, B.M. & Breedlove, S.M. 2002b. Differences in ﬁnger length ratios between self-identiﬁed “butch” and “femme”. Archives of Sexual Behavior 31: 123-127.
Burley, N. & Foster, V. 2004. Digit ratio varies with sex, egg order and strength of mate preference in zebra ﬁnches. Proceedings of the Royal Society B: Biological Sciences 271: 239-244.
Chang, J.L. 2008. Sexual dimorphism of the second-to-fourth digit length ratio (2D:4D) in the strawberry poison dart frog (Oophaga pumilio) in Costa Rica. Journal of Herpetology 42: 414-416.
Chang, J., Doughty, J. Wade, L. & Lovern, M. 2006. Sexual dimorphism in the second-to-fourth digit length ratio in Green Anoles, Anolis carolinensis (Squamata: Polychrotidae) from the southeastern United States. Canadian Journal of Zoology 84: 1489-1494.
Fink, B., Grammer, K., Mitteroecker, P., Gunz, P., Schaefer, K., Bookstein, F. & Manning, J. 2005. Second to fourth digit ratio and face shape. Proceedings of the Royal Society B: Biological Sciences 272: 1995-2001.
Flegr, J., Hruskova, M., Hodny, Z., Novotna, M., & Hanusova, J. 2005. Body height, body mass index, waist-hip ratio, ﬂuctuating asymmetry and second to fourth digit ratio in subjects with latent toxoplasmosis. Parasitology 130: 621-628.
Kempel, P., Gohlke, B., Klempau, J., Zinsberger, P., Reuter, M. & Hennig, J. 2005. Second-to-fourth digit length, testosterone and spatial ability. Intelligence 33: 215-230.
Kondo, T., Zakany, J., Innis, J. & Duboule, D. 1997. Of ﬁngers, toes and penises. Nature 390: 29.
Krumlauf, R. 1994. Hox genes in vertebrate development Cell 78: 191-201.
Leoni, B., Canova, L. & Saino, N. 2005. Sexual dimorphism in metapodial and phalanges length ratios in the wood mouse. The Anatomical Record Part A Discoveries in Molecular Cellular and Evolutionary Biology 286A: 955-961.
McFadden, D. & Shubel, E. 2002. Relative lengths of ﬁnger and toes in human males and females. Hormones and Behavior 42: 492-500.
McFadden, D. & Bracht, M. 2003. The relative lengths and weights of metacarpals and metatarsals in baboons (Papio hamadryas). Hormones and Behavior 43: 347-355.
McFadden, D. & Bracht, M. 2005. Sex differences in the relative lengths of metacarpals and metatarsals in gorillas and chimpanzees. Hormones and Behavior 47: 99-111.
McIntyre, M., Ellison, P., Lieberman, D., Demerath, E. & Towne, B. 2005. The development of sex differences in digital formula from infancy in the Fels longitudinal study. Proceedings of the Royal Society B: Biological Sciences 272: 1473-1479.
Manning, J. 2002. Digit ratio. New Brunswick, NJ: Rutgers University Press.
Manning, J., Scutt, D., Wilson, J. & Lewis-Jones, D. 1998. The ratio of 2nd to 4th digit length: a predictor of sperm number and levels of testosterone, LH and oestrogen. Human Reproduction 13: 3000-3004.
Manning, J., Callow, M. & Bundred, P. 2003. Finger and toes ratios in humans and mice: implications for the etiology of diseases inﬂuenced by HOX genes. Medical Hypotheses 60: 340-343.
Mortlock, D. & Innis, J. 1997. Mutation of HOXA13 in hand-foot genital syndrome. Nature Genetics 15: 179-180.
Noghanchi, E. & Javanbakht, H. 2019. Study of Sexual Dimorphism in Second-to-Fourth Digit Length Ratio (2D: 4D) in the Green-Bellied Lizard (Darevskia cholorogaster) from Iran. Journal of Genetic Resources 5: 45-50.
Peters, M., Mackenzie, K. & Bryden, P. 2002. Finger length and distal ﬁnger extent patterns in human. American Journal of Physical Anthropology 117: 209-217.
Rajabi, F. & Javanbakht, H. 2019. Sexual Dimorphism in Digit Length Ratios in Marsh Frog, Pelophylax ridibundus (Ranidae) from Iran. Journal of Applied Biological Sciences 13: 33-36.
Utz, D., Gaulin, S., Sporter, R. & McBurney, D. 2004. Sex hormones and ﬁnger length. What does 2D:4D indicate? Evolution and Human Behavior 25: 182-199.
Romano, M., Rubolini, D., Martinelli, R., Bonisoli, A. & Saino, N. 2005. Experimental manipulation of yolk testosterone affects digit length ratios in the ring-necked pheasant (Phasianus colchicus). Hormones and Behavior 48: 342-346.
Romano, M., Leoni, B. & Saino, N. 2006. Examination marks of male university students positively correlate with ﬁnger length ratios (2D:4D). Biological Psychology 71: 175-182.
Roney, J., Whitham, J., Leoni, M, Bellem, A, Wielebnowski, N, & Maestripieri, D. 2004. Relative digit lengths and testosterone levels in Guinea baboons. Hormones and Behavior 45: 285-290.
Rubolini, D., Pupin, F., Sacchi, A., Gentilli, M., Zuffi, P., Galeotti, H. & Saino, N. 2006. Sexual dimorphism in digit length ratios in two lizard species. Anatomical Record 288: 491-497.
Trivers, R., Manning, J. & Jacobson, A. 2006. A longitudinal study of digit ratio (2D:4D) and other ﬁnger ratios in Jamaican children. Hormones and Behavior 49: 150-156.
Williams, T., Pepitone, M., Christensen, S., Cooke, B., Huberman, A., Breedlove, N., Breedlove, T., Jordan, C. & Breedlove, S. 2000. Finger-length ratios and sexual orientation. Nature 404: 455-456.