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

10.7934/p3551 ◽  
2021 ◽  
Author(s):  
P Sánchez-Martínez ◽  
J Daza ◽  
J Hoyos
Keyword(s):  
Middle Ear ◽  
Comparative Anatomy ◽  
Lizard Species ◽  
Evolutionary Changes

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

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11722
Author(s):  
Paola María Sánchez-Martínez ◽  
Juan D. Daza ◽  
Julio Mario Hoyos
Keyword(s):  
Middle Ear ◽  
Comparative Anatomy ◽  
General Structure ◽  
Main Function ◽  
Ancestral State ◽  
Sound Waves ◽  
Ancestral Reconstruction ◽  
Lizard Species ◽  
Evolutionary Changes ◽  
Axis Length

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.

scholarly journals The comparative anatomy of the pig middle ear cavity: a model for middle ear inflammation in the human?

1998 ◽  
Vol 192 (3) ◽  
pp. 359-368 ◽  
Author(s):  
J. P. PRACY ◽  
A. WHITE ◽  
Y. MUSTAFA ◽  
D. SMITH ◽  
M. E. PERRY
Keyword(s):  
Middle Ear ◽  
Comparative Anatomy

Comparative Anatomy of Eustachian Tube and Middle Ear Cavity in Animal Models for Otitis Media

1982 ◽  
Vol 91 (1) ◽  
pp. 82-89 ◽  
Author(s):  
Hal J. Daniel ◽  
Jack E. Brinn ◽  
Robert S. Fulghum ◽  
Kathryn A. Barrett
Keyword(s):  
Animal Models ◽  
Otitis Media ◽  
Eustachian Tube ◽  
Middle Ear ◽  
Animal Species ◽  
Comparative Anatomy ◽  
Goblet Cells ◽  
Naturally Occurring ◽  
High Incidence ◽  
Seromucous Glands

The comparative anatomy of the normal eustachian tube (ET) and normal middle ear cavity of three animal species (rat, gerbil, and chinchilla) is described relating to the usefulness of these animals as models for otitis media (OM). Routine histological and anatomical techniques and procedures were used. The gerbil and chinchilla, although of different sizes, are quite similar, having hypertrophied middle ear bullae, nearly vertical ET, and similar histology including seromucous glands draining directly into the ET. In contrast, the rat has a small bulla, a nearly horizontal ET, and a large concentration of goblet cells but few mucous glands in the ET. It appears that the chinchilla and the gerbil may serve as alternative models for OM research. Chinchillas and gerbils are relatively free of naturally occurring OM, while the rat has a high incidence of naturally occurring OM.

scholarly journals Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals

2020 ◽  
Author(s):  
Fangyuan Mao ◽  
Cunyu Liu ◽  
Morgan Hill Chase ◽  
Andrew K Smith ◽  
Jin Meng
Keyword(s):  
Middle Ear ◽  
Early Cretaceous ◽  
Convergent Evolution ◽  
Evolutionary Development ◽  
Hinge Joint ◽  
Evolution And Development ◽  
Evolutionary Changes ◽  
Mesozoic Mammals ◽  
Jaw Joint

Abstract We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.

scholarly journals Flexibility within the middle ears of vertebrates

2012 ◽  
Vol 127 (1) ◽  
pp. 2-14 ◽  
Author(s):  
M J Mason ◽  
M R B Farr
Keyword(s):  
Inner Ear ◽  
Middle Ear ◽  
Comparative Anatomy ◽  
High Amplitude ◽  
Prosthesis Design ◽  
Clinical Implications ◽  
Sound Energy ◽  
Common Features ◽  
Simple Models

AbstractIntroduction and aims:Tympanic middle ears have evolved multiple times independently among vertebrates, and share common features. We review flexibility within tympanic middle ears and consider its physiological and clinical implications.Comparative anatomy:The chain of conducting elements is flexible: even the ‘single ossicle’ ears of most non-mammalian tetrapods are functionally ‘double ossicle’ ears due to mobile articulations between the stapes and extrastapes; there may also be bending within individual elements.Simple models:Simple models suggest that flexibility will generally reduce the transmission of sound energy through the middle ear, although in certain theoretical situations flexibility within or between conducting elements might improve transmission. The most obvious role of middle-ear flexibility is to protect the inner ear from high-amplitude displacements.Clinical implications:Inter-ossicular joint dysfunction is associated with a number of pathologies in humans. We examine attempts to improve prosthesis design by incorporating flexible components.

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