Mixed Sex Effects on the Second-to-Fourth Digit Ratio of Túngara Frogs (Engystomops pustulosus) and Cane Toads (Rhinella marina)

Lynne Beaty, Quinn C. Emmering, Ximena E. Bernal

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Sexual dimorphism in the ratio of digit lengths has been correlated to behavioral, physiological, and morphological traits in a variety of taxa. While sexual dimorphism in the second-to-fourth digit length ratio (2D:4D) is a well-established indicator of prenatal androgen exposure in mammals, investigations into the patterns of 2D:4D and the drivers of such variation in other taxa are lacking. We used linear mixed effects models to gain a mechanistic understanding of the factors that drive variation in the scaling relationship between the lengths of the second and fourth digits in two species of anurans: túngara frogs (Engystomops pustulosus) and cane toads (Rhinella marina). We found evidence for sexual dimorphism of the 2D:4D scaling relationship on the front feet of túngara frogs, with female frogs having a larger ratio than males resulting from a relatively longer second digit on females. To our knowledge, this mammal-like pattern of sex differences in digit ratio has not yet been reported for anurans. However, given the reduced number of digits on the front feet of anurans, and uncertainty about which digit was lost during evolutionary history, this apparent sexual dimorphism in the front feet of túngara frogs should be treated with caution. In contrast, we found no evidence of sexual dimorphism in 2D:4D on either the front or rear feet of cane toads. This study highlights ambiguities in 2D:4D across taxa and suggests that further research is needed to evaluate the effect of androgens on 2D:4D in animals other than placental mammals.

Original languageEnglish (US)
Pages (from-to)421-427
Number of pages7
JournalAnatomical Record
Volume299
Issue number4
DOIs
StatePublished - Apr 1 2016

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Bufo marinus
Canes
toad
sexual dimorphism
marina
Sex Characteristics
frog
Anura
frogs
gender
mammal
androgen
Mammals
mammals
androgens
Androgens
Foot
gender differences
uncertainty
Uncertainty

All Science Journal Classification (ASJC) codes

  • Anatomy
  • Biotechnology
  • Histology
  • Ecology, Evolution, Behavior and Systematics

Cite this

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title = "Mixed Sex Effects on the Second-to-Fourth Digit Ratio of T{\'u}ngara Frogs (Engystomops pustulosus) and Cane Toads (Rhinella marina)",
abstract = "Sexual dimorphism in the ratio of digit lengths has been correlated to behavioral, physiological, and morphological traits in a variety of taxa. While sexual dimorphism in the second-to-fourth digit length ratio (2D:4D) is a well-established indicator of prenatal androgen exposure in mammals, investigations into the patterns of 2D:4D and the drivers of such variation in other taxa are lacking. We used linear mixed effects models to gain a mechanistic understanding of the factors that drive variation in the scaling relationship between the lengths of the second and fourth digits in two species of anurans: t{\'u}ngara frogs (Engystomops pustulosus) and cane toads (Rhinella marina). We found evidence for sexual dimorphism of the 2D:4D scaling relationship on the front feet of t{\'u}ngara frogs, with female frogs having a larger ratio than males resulting from a relatively longer second digit on females. To our knowledge, this mammal-like pattern of sex differences in digit ratio has not yet been reported for anurans. However, given the reduced number of digits on the front feet of anurans, and uncertainty about which digit was lost during evolutionary history, this apparent sexual dimorphism in the front feet of t{\'u}ngara frogs should be treated with caution. In contrast, we found no evidence of sexual dimorphism in 2D:4D on either the front or rear feet of cane toads. This study highlights ambiguities in 2D:4D across taxa and suggests that further research is needed to evaluate the effect of androgens on 2D:4D in animals other than placental mammals.",
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Mixed Sex Effects on the Second-to-Fourth Digit Ratio of Túngara Frogs (Engystomops pustulosus) and Cane Toads (Rhinella marina). / Beaty, Lynne; Emmering, Quinn C.; Bernal, Ximena E.

In: Anatomical Record, Vol. 299, No. 4, 01.04.2016, p. 421-427.

Research output: Contribution to journalArticle

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