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Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata

The skeleton of the middle ear of lizards is composed of three anatomical elements: columella, extracolumella, and tympanic membrane, with some exceptions that show modifications of this anatomy. The main function of the middle ear is transforming sound waves into vibrations and transmitting these t...

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Autores principales: Sánchez-Martínez, Paola María, Daza, Juan D., Hoyos, Julio Mario
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PeerJ Inc. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8310623/
https://www.ncbi.nlm.nih.gov/pubmed/34327053
http://dx.doi.org/10.7717/peerj.11722
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author Sánchez-Martínez, Paola María
Daza, Juan D.
Hoyos, Julio Mario
author_facet Sánchez-Martínez, Paola María
Daza, Juan D.
Hoyos, Julio Mario
author_sort Sánchez-Martínez, Paola María
collection PubMed
description The skeleton of the middle ear of lizards is composed of three anatomical elements: columella, extracolumella, and tympanic membrane, with some exceptions that show modifications of this anatomy. The main function of the middle ear is transforming sound waves into vibrations and transmitting these to the inner ear. Most middle ear studies mainly focus on its functional aspects, while few describe the anatomy in detail. In lizards, the morphology of the columella is highly conservative, while the extracolumella shows variation in its presence/absence, size, and the number of processes present on the structure. In this work, we used diaphanized and double-stained specimens of 38 species of lizards belonging to 24 genera to study the middle ear’s morphology in a comparative framework. Results presented here indicate more variation in the morphology of the extracolumella than previously known. This variation in the extracolumella is found mainly in the pars superior and anterior processes, while the pars inferior and the posterior process are more constant in morphology. We also provide new information about the shape of gekkotan extracolumella, including traits that are diagnostic for the iguanid and gekkonid middle ear types. The data collected in this study were combined with information from published descriptive works. The new data included here refers to the length of the columella relative to the extracolumella central axis length, the general structure of the extracolumella, and the presence of the internal process. These characters were included in ancestral reconstruction analysis using Bayesian and parsimony approaches. The results indicate high levels of homoplasy in the variation of the columella-extracolumella ratio, providing a better understanding of the ratio variation among lizards. Additionally, the presence of four processes in the extracolumella is the ancestral state for Gekkota, Pleurodonta, and Xantusiidae, and the absence of the internal processes is the ancestral state for Gekkota, Gymnophthalmidae, and Scincidae; despite the fact that these groups convergently develop these character states, they could be used in combination with other characters to diagnose these clades. The posterior extension in the pars superior and an anterior process with some small and sharp projections is also a diagnostic trait for Gekkota. A more accurate description of each process of the extracolumella and its variation needs to be evaluated in a comprehensive analysis, including a greater number of species. Although the number of taxa sampled in this study is small considering the vast diversity of lizards, the results provide an overall idea of the amount of variation of the middle ear while helping to infer the evolutionary history of the lizard middle ear.
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spelling pubmed-83106232021-07-28 Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata Sánchez-Martínez, Paola María Daza, Juan D. Hoyos, Julio Mario PeerJ Evolutionary Studies The skeleton of the middle ear of lizards is composed of three anatomical elements: columella, extracolumella, and tympanic membrane, with some exceptions that show modifications of this anatomy. The main function of the middle ear is transforming sound waves into vibrations and transmitting these to the inner ear. Most middle ear studies mainly focus on its functional aspects, while few describe the anatomy in detail. In lizards, the morphology of the columella is highly conservative, while the extracolumella shows variation in its presence/absence, size, and the number of processes present on the structure. In this work, we used diaphanized and double-stained specimens of 38 species of lizards belonging to 24 genera to study the middle ear’s morphology in a comparative framework. Results presented here indicate more variation in the morphology of the extracolumella than previously known. This variation in the extracolumella is found mainly in the pars superior and anterior processes, while the pars inferior and the posterior process are more constant in morphology. We also provide new information about the shape of gekkotan extracolumella, including traits that are diagnostic for the iguanid and gekkonid middle ear types. The data collected in this study were combined with information from published descriptive works. The new data included here refers to the length of the columella relative to the extracolumella central axis length, the general structure of the extracolumella, and the presence of the internal process. These characters were included in ancestral reconstruction analysis using Bayesian and parsimony approaches. The results indicate high levels of homoplasy in the variation of the columella-extracolumella ratio, providing a better understanding of the ratio variation among lizards. Additionally, the presence of four processes in the extracolumella is the ancestral state for Gekkota, Pleurodonta, and Xantusiidae, and the absence of the internal processes is the ancestral state for Gekkota, Gymnophthalmidae, and Scincidae; despite the fact that these groups convergently develop these character states, they could be used in combination with other characters to diagnose these clades. The posterior extension in the pars superior and an anterior process with some small and sharp projections is also a diagnostic trait for Gekkota. A more accurate description of each process of the extracolumella and its variation needs to be evaluated in a comprehensive analysis, including a greater number of species. Although the number of taxa sampled in this study is small considering the vast diversity of lizards, the results provide an overall idea of the amount of variation of the middle ear while helping to infer the evolutionary history of the lizard middle ear. PeerJ Inc. 2021-07-22 /pmc/articles/PMC8310623/ /pubmed/34327053 http://dx.doi.org/10.7717/peerj.11722 Text en © 2021 Sánchez-Martínez et al. https://creativecommons.org/licenses/by/4.0/This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.
spellingShingle Evolutionary Studies
Sánchez-Martínez, Paola María
Daza, Juan D.
Hoyos, Julio Mario
Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title_full Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title_fullStr Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title_full_unstemmed Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title_short Comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within Squamata
title_sort comparative anatomy of the middle ear in some lizard species with comments on the evolutionary changes within squamata
topic Evolutionary Studies
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8310623/
https://www.ncbi.nlm.nih.gov/pubmed/34327053
http://dx.doi.org/10.7717/peerj.11722
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