Age effects and size effects in the ears of gekkonomorph lizards: inner ear

Gehr, Daniel D.; Werner, Yehudah L.

doi:10.1016/j.heares.2004.08.013

Cited by 11 publications

(15 citation statements)

References 47 publications

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“…The middle-ear morphological data used here for the correlation analyses were the same reported earlier [44,51], as were those for the inner ear [15]. However, statistical considerations constrain the number of variables relative to the number of individuals.…”

Section: Morphologymentioning

confidence: 98%

“…9a,b): Even after removal of the middle-ear system, the CAP sensitivity of adults exceeded that of juveniles (at least in Eublepharis macularius) despite the fact that the length of the basilar papilla and number of hair cells were unchanged [15]. The apparent effect of body length on CAP could be due to several agerelated changes, and we propose that at least two sizerelated morphological changes, previously not considered in this context, are likely to participate in this effect.…”

Section: Introductionmentioning

confidence: 99%

“…Previous reports have described the velocity transfer function of sound-driven tympanic membrane responses [50], inner-ear dimensions with estimates of hair-cell number [15,16], and quantitative morphology of various middle-ear conductive structures [51].…”

Section: Introductionmentioning

confidence: 99%

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Effects of age and size in the ears of gekkotan lizards: auditory sensitivity, its determinants, and new insights into tetrapod middle-ear function

Werner

Montgomery

Seifan

et al. 2008

Pflugers Arch - Eur J Physiol

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Do related, differently sized species differ in size-related structural or functional traits merely because they mature at different points of a uniform allometric ontogenetic growth curve, or do they evolutionarily diverge? We tested ears of gekkotan lizards through experiments distinguishing the two. Auditory sensitivity was assessed by compound action potential (CAP) thresholds in eight species. The best thresholds characterizing species ranged 22-72 dB sound pressure level at 0.5-1.0 kHz. Direct acoustic stimulation of the columella footplate elevated thresholds by 25-50 dB. Intraspecific CAP sensitivity was primarily affected by body length in Eublepharis macularius, but by tympanic-membrane velocity in Oedura marmorata. The chief factor determining middle-ear function (difference in CAP sensitivity before and after middle-ear ablation) was body length in both species. A secondary factor was the middle-ear hydraulic lever ratio in E. macularius, but the mechanical lever in O. marmorata. When intra- and interspecific data were compared, the relation of CAP thresholds to body size in E. macularius resembled the interspecific regression. The intraspecific regression of auditory sensitivity over tympanic membrane velocity in O. marmorata differed from that calculated interspecifically. Hence, the evolutionary contribution to size effects on CAP sensitivity exceeds the ontogenetic contribution. Putatively, body length affects CAP sensitivity through absolute sizes of tympanic membrane and columella footplate. These newly discovered effects join those of the hydraulic lever and (interspecifically) hair-cell number to improve the hearing of larger species that vocally communicate across wider spaces, apparently throughout the Tetrapoda.

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Section: Morphologymentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Effects of age and size in the ears of gekkotan lizards: auditory sensitivity, its determinants, and new insights into tetrapod middle-ear function

Werner

Montgomery

Seifan

et al. 2008

Pflugers Arch - Eur J Physiol

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“…Mechanisms for such an age-related difference might vary across gecko species, but appear partially attributable to changes in middle-ear function related to body size/ length (Werner et al 2002(Werner et al , 2008. Previous anatomical studies (Miller 1985;Gehr and Werner 2005) suggest the lizard inner ear is fairly well-formed at birth, though juvenile Eublepharis and adult Coleonyx appear remarkably similar in appearance and external size. Given the relative similarity in emissions between juvenile and adult Eublepharis (and their contrast to Coleonyx data), the present results suggest that OAE properties derive primarily from characteristics of the inner ear.…”

Section: Juvenile Versus Adultmentioning

confidence: 99%

“…Based upon overall body size/appearance, juvenile Eublepharis and adult Coleonyx are similar (see Table 1). There is evidence that lizard inner ear morphology is relatively independent of age (Miller 1985;Gehr and Werner 2005), indicating that the juvenile Eublepharis inner ear morphology is adult-like. Thus, juvenile Eublepharis has a body size similar to adult Coleonyx, but inner ear dimensions similar to adult Eublepharis.…”

Section: Basis For a Comparative Studymentioning

confidence: 99%

Comparison of Otoacoustic Emissions Within Gecko Subfamilies: Morphological Implications for Auditory Function in Lizards

Bergevin

2010

JARO

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Otoacoustic emissions (OAEs) are sounds emitted by the ear and provide a non-invasive probe into mechanisms underlying peripheral auditory transduction. This study focuses upon a comparison of emission properties in two phylogenetically similar pairs of gecko: Gekko gecko and Hemidactylus turcicus and Eublepharis macularius and Coleonyx variegatus. Each pair consists of two closely related species within the same subfamily, with quantitatively known morphological properties at the level of the auditory sensory organ (basilar papilla) in the inner ear. Essentially, the comparison boils down to an issue of size: how does overall body size, as well as the innerear dimensions (e.g., papilla length and number of hair cells), affect peripheral auditory function as inferred from OAEs? Estimates of frequency selectivity derived from stimulus-frequency emissions (emissions evoked by a single low-level tone) indicate that tuning is broader in the species with fewer hair cells/shorter papilla. Furthermore, emissions extend outwards to higher frequencies (for similar body temperatures) in the species with the smaller body size/narrower interaural spacing. This observation suggests the smaller species have relatively improved high-frequency sensitivity, possibly related to vocalizations and/or aiding azimuthal sound localization. For one species (Eublepharis), emissions were also examined in both juveniles and adults. Qualitatively similar emission properties in both suggests that inner-ear function is adult like soon after hatching and that external body size (e.g., middle-ear dimensions and interaural spacing) has a relatively small impact upon emission properties within a species.

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Vocalization by extant nonavian reptiles: A synthetic overview of phonation and the vocal apparatus

Russell

Bauer

2020

The Anatomical Record

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Among amniote vertebrates, nonavian reptiles (chelonians, crocodilians, and lepidosaurs) are regarded as using vocal signals rarely (compared to birds and mammals). In all three reptilian clades, however, certain taxa emit distress calls and advertisement calls using modifications of regions of the upper respiratory tract. There is no central tendency in either acoustic mechanisms or the structure of the vocal apparatus, and many taxa that vocalize emit only relatively simple sounds. Available evidence indicates multiple origins of true vocal abilities within these lineages. Reptiles thus provide opportunities for studying the early evolutionary stages of vocalization. The early literature on the diversity of form of the laryngotracheal apparatus of reptiles boded well for the study of form-function relationships, but this potential was not extensively explored. Emphasis shifted away from anatomy, however, and centered instead on acoustic analysis of the sounds that are produced. New investigative techniques have provided novel ways of studying the form-function aspects of the structures involved in phonation and have brought anatomical investigation to the forefront again. In this review we summarize what is known about hearing in reptiles in order to contextualize the vocal signals they generate and the sound-producing mechanisms responsible for them. The diversity of form of the sound producing apparatus and the increasing evidence that reptiles are more dependent upon vocalization as a communication medium than previously thought indicates that they have a significant role to play in the understanding of the evolution of vocalization in amniotes.

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Age effects and size effects in the ears of gekkonomorph lizards: inner ear

Cited by 11 publications

References 47 publications

Effects of age and size in the ears of gekkotan lizards: auditory sensitivity, its determinants, and new insights into tetrapod middle-ear function

Effects of age and size in the ears of gekkotan lizards: auditory sensitivity, its determinants, and new insights into tetrapod middle-ear function

Comparison of Otoacoustic Emissions Within Gecko Subfamilies: Morphological Implications for Auditory Function in Lizards

Vocalization by extant nonavian reptiles: A synthetic overview of phonation and the vocal apparatus

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