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Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency

INTRODUCTION: Despite the growing number of studies describing digit ratio patterns in tetrapods, knowledge concerning certain basic issues is still scarce. In lower vertebrates such as tailless amphibians (Anura), the numbering of individual fingers on the forelimbs and their homology with the fing...

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Autores principales: Kaczmarski, Mikołaj, Kaczmarek, Jan M., Jankowiak, Łukasz, Kolenda, Krzysztof, Tryjanowski, Piotr
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7992345/
https://www.ncbi.nlm.nih.gov/pubmed/33766147
http://dx.doi.org/10.1186/s40851-021-00174-y
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author Kaczmarski, Mikołaj
Kaczmarek, Jan M.
Jankowiak, Łukasz
Kolenda, Krzysztof
Tryjanowski, Piotr
author_facet Kaczmarski, Mikołaj
Kaczmarek, Jan M.
Jankowiak, Łukasz
Kolenda, Krzysztof
Tryjanowski, Piotr
author_sort Kaczmarski, Mikołaj
collection PubMed
description INTRODUCTION: Despite the growing number of studies describing digit ratio patterns in tetrapods, knowledge concerning certain basic issues is still scarce. In lower vertebrates such as tailless amphibians (Anura), the numbering of individual fingers on the forelimbs and their homology with the fingers of other vertebrates pose an unsolved problem. Based on reviewed data on anuran limb development, we argue that the correct finger numbering scheme should be based on the assumption that the first finger, not the fifth finger, was reduced on the forelimbs. We analyzed the digit ratio in the common toad (Bufo bufo, Bufonidae), a species characterized by well-developed sexual dimorphism whereby females are larger than males, using both numbering schemes present in the literature. RESULTS: We found that the digit ratio on hindlimbs differed significantly between the sexes only in the cases of left 2D:3D, with lower digit ratios in females, and of left 3D:4D, with lower digit ratios in males. We found that sex was the only significant variable for forelimbs, differentiating 2D:3D on the left forelimb, with lower digit ratios in females; 2D:4D on the right forelimb, with lower digit ratios in males; and 3D:4D on both forelimbs, with lower digit ratios in males. These results relate to variant II reflecting the hypothesis that the first digit was reduced during phylogenesis. There was no relationship between the body size (SVL) of individuals and any digit ratio, excluding 2D:4D on the right forelimbs in models with age variables. Additionally, for a subset of data where individual age was known, the models indicated that age was linked to significant differences in 2D:4D and 3D:4D on the left hindlimbs, while age, SVL, and sex influenced 2D:4D on the right forelimbs. CONCLUSION: We emphasize the importance of the problem of the correct numbering of forelimb digits in Anura and, under the assumption that it was the fifth digit that was reduced, argue that earlier results on digit ratio in this group should be interpreted with caution. The detected relationship between digit ratio and age in amphibians expands our knowledge, indicating that the age of individuals should be included in future digit ratio studies. This relationship may also apply to studies using digit ratio as a noninvasive indicator of endocrine disruption in amphibians. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40851-021-00174-y.
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spelling pubmed-79923452021-03-25 Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency Kaczmarski, Mikołaj Kaczmarek, Jan M. Jankowiak, Łukasz Kolenda, Krzysztof Tryjanowski, Piotr Zoological Lett Research Article INTRODUCTION: Despite the growing number of studies describing digit ratio patterns in tetrapods, knowledge concerning certain basic issues is still scarce. In lower vertebrates such as tailless amphibians (Anura), the numbering of individual fingers on the forelimbs and their homology with the fingers of other vertebrates pose an unsolved problem. Based on reviewed data on anuran limb development, we argue that the correct finger numbering scheme should be based on the assumption that the first finger, not the fifth finger, was reduced on the forelimbs. We analyzed the digit ratio in the common toad (Bufo bufo, Bufonidae), a species characterized by well-developed sexual dimorphism whereby females are larger than males, using both numbering schemes present in the literature. RESULTS: We found that the digit ratio on hindlimbs differed significantly between the sexes only in the cases of left 2D:3D, with lower digit ratios in females, and of left 3D:4D, with lower digit ratios in males. We found that sex was the only significant variable for forelimbs, differentiating 2D:3D on the left forelimb, with lower digit ratios in females; 2D:4D on the right forelimb, with lower digit ratios in males; and 3D:4D on both forelimbs, with lower digit ratios in males. These results relate to variant II reflecting the hypothesis that the first digit was reduced during phylogenesis. There was no relationship between the body size (SVL) of individuals and any digit ratio, excluding 2D:4D on the right forelimbs in models with age variables. Additionally, for a subset of data where individual age was known, the models indicated that age was linked to significant differences in 2D:4D and 3D:4D on the left hindlimbs, while age, SVL, and sex influenced 2D:4D on the right forelimbs. CONCLUSION: We emphasize the importance of the problem of the correct numbering of forelimb digits in Anura and, under the assumption that it was the fifth digit that was reduced, argue that earlier results on digit ratio in this group should be interpreted with caution. The detected relationship between digit ratio and age in amphibians expands our knowledge, indicating that the age of individuals should be included in future digit ratio studies. This relationship may also apply to studies using digit ratio as a noninvasive indicator of endocrine disruption in amphibians. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40851-021-00174-y. BioMed Central 2021-03-25 /pmc/articles/PMC7992345/ /pubmed/33766147 http://dx.doi.org/10.1186/s40851-021-00174-y Text en © The Author(s) 2021 Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
spellingShingle Research Article
Kaczmarski, Mikołaj
Kaczmarek, Jan M.
Jankowiak, Łukasz
Kolenda, Krzysztof
Tryjanowski, Piotr
Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title_full Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title_fullStr Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title_full_unstemmed Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title_short Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency
title_sort digit ratio in the common toad bufo bufo: the effects of reduced fingers and of age dependency
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7992345/
https://www.ncbi.nlm.nih.gov/pubmed/33766147
http://dx.doi.org/10.1186/s40851-021-00174-y
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