The Middle Ear of Reptiles and Birds

Saunders, James C.; Duncan, R. Keith; Doan, Daryl E.; Werner, Yehudah L.

doi:10.1007/978-1-4612-1182-2_2

Cited by 59 publications

(79 citation statements)

References 76 publications

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“…The tympana of all species show a band-pass characteristic with maximal response around 1-3·kHz, where the peak vibration velocity amplitudes range from 1.7 to 4.9·mm·s -1 ·Pa -1 (Table·1), comparable to earlier measurements from gekkonid lizards (2-4·mm·s -1 at 100·dB·SPL; Manley, 1992;Saunders et al, 2000;Werner et al, 2002). The non-linear decrease in vibration amplitude at high sound levels in Gekko (Fig.·1B) is probably due to a middle-ear muscle found in geckos that may reduce the columellar vibrations, analogous to the stapedial reflex of mammals (Wever, 1978).…”

Section: Discussionsupporting

confidence: 85%

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Directionality of the lizard ear

Christensen‐Dalsgaard¹,

Manley

2005

Journal of Experimental Biology

115

111

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SUMMARY Lizards have highly sensitive ears, but most lizard heads are small (1-2 cm in diameter) compared to the wavelengths of sound of frequencies to which they are most sensitive (1-4 kHz, wavelengths 34-8.5 cm). Therefore, the main cues to sound direction that mammals use - binaural time and intensity cues due to arrival-time differences and sound shadowing by the head - will be very small in lizards. The present work shows that acoustical coupling of the two eardrums in lizards produces the largest directionality of any terrestrial vertebrate ear studied. Laser vibrometric studies of tympanic motion show pronounced directionality within a 1.8-2.4 kHz frequency band around the best frequency of hearing, caused by the interference of ipsi- and contralateral inputs. The results correspond qualitatively to the response of a simple middle ear model,assuming coupling of the tympana through a central cavity. Furthermore,observed directional responses are markedly asymmetrical, with a steep gradient of up to 50-fold (34 dB) response differences between ipsi- and contralateral frontal angles. Therefore, the directionality is easily exploitable by simple binaural subtraction in the brain. Lizard ears are the clearest vertebrate examples of directionality generated by tympanic coupling.

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Section: Discussionsupporting

confidence: 85%

“…Their best frequencies of hearing range from 1 to 3·kHz, and the eardrum vibrations show band-pass characteristics (Saunders et al, 2000). The high-frequency sensitivity is influenced by the mechanics of the auditory ossicle and the extracolumella (Manley, 1990;Werner et al, 1998).…”

mentioning

confidence: 99%

Directionality of the lizard ear

Christensen‐Dalsgaard¹,

Manley

2005

Journal of Experimental Biology

115

111

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“…In birds and mammals, the middle-ear muscles apparently protect the ear from the individual's own vocalisations, as reviewed by Saunders et al (Saunders et al, 2000). A similar arrangement occurs in vocalising lizards and geckos (Wever, 1978).…”

Section: Behavioural Ecological and Evolutionary Aspectsmentioning

confidence: 90%

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Werner

Pylka

Schneider

et al. 2009

Journal of Experimental Biology

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SUMMARYThe dimorphic ear of the bullfrog, Rana catesbeiana, has long been enigmatic. The male's tympanic membrane (TM) area approximates twice the area of the female's; however, similar size differences in the area of the columellar footplate were not observed between the sexes. Hence, the male's hearing is expected to be more sensitive than the female's but this is not the case. Asking what offsets the advantage of the large TM, we applied a series of experiments to the auditory system. Male and female audiograms based on stimulation with airborne sound and on both multi-unit responses from the brain and alternating cochlear potentials ('microphonics') showed equal sensitivity and a small difference in frequency response; at low frequencies the male was more sensitive than the female. Amputating the columella and stimulating the stump with mechanical vibration showed that for an equal microphonic response, the male's footplate vibrated with lower amplitude than the female's footplate. Mechanically stimulating the TM of the intact ear replicated this result, excluding the involvement of the mechanical lever. The TM of the male weighs five times the TM of the female, and artificial loading of the TM of either sex greatly reduced the ear's sensitivity. Hence, the male's excessive area ratio (TM to columellar footplate) is offset by the heavier cartilage cushion on the male's TM, damping the TM's response to sound. This is corroborated by experimentally artificially loading the TM. The product of area ratio and footplate vibration amplitude would result in similar stimulation of the inner ear in the two sexes.

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“…Of these, the infrastapedial process extends towards the edge of the tympanic membrane and in some species articulates with its supporting bony rim. 22,36 Based on a consideration of the anatomy and micromanipulation of the structures involved, the extrastapes…”

Section: Reptile Middle Earsmentioning

confidence: 99%

“…Hearing tends to be limited to the sonic range in non-mammalian vertebrates, 22,87,88 although Feng et al 89 report an exception. Sound localisation at low frequencies is made possible in these animals through the use of their acoustically coupled ears as pressure-difference receivers.…”

Section: Flexibility Within the Middle Ear Of Vertebratesmentioning

confidence: 99%

Flexibility within the middle ears of vertebrates

Mason

Farr

2012

J. Laryngol. Otol.

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Introduction 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 nonmammalian 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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The Middle Ear of Reptiles and Birds

Cited by 59 publications

References 76 publications

Directionality of the lizard ear

Directionality of the lizard ear

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Flexibility within the middle ears of vertebrates

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