The Reptile Ear

Wever, Ernest Glen

doi:10.1515/9780691196664

Cited by 101 publications

(66 citation statements)

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“…The membranous labyrinth of the inner ear, composed of sensory structures for both the auditory and equilibrium systems 23,24 , is also encapsulated by bone. In general, the bone sits quite close to the membranous labyrinth and the morphology of certain components, such as the semicircular canals, are therefore well represented in the morphology of the surrounding bone.…”

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confidence: 99%

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

Dudgeon

Maddin

Evans

et al. 2020

Sci Rep

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Although isolated Champsosaurus remains are common in Upper cretaceous sediments of north America, the braincase of these animals is enigmatic due to the fragility of their skulls. Here, two wellpreserved specimens of Champsosaurus (CMN 8920 and CMN 8919) are CT scanned to describe their neurosensory structures and infer sensory capability. the anterior portion of the braincase was poorly ossified and thus does not permit visualization of a complete endocast; however, impressions of the olfactory stalks indicate that they were elongate and likely facilitated good olfaction. the posterior portion of the braincase is ossified and morphologically similar to that of other extinct diapsids. The absence of an otic notch and an expansion of the pars inferior of the inner ear suggests Champsosaurus was limited to detecting low frequency sounds. comparison of the shapes of semicircular canals with lepidosaurs and archosauromorphs demonstrates that the semicircular canals of Champsosaurus are most similar to those of aquatic reptiles, suggesting that Champsosaurus was well adapted for sensing movement in an aquatic environment. this analysis also demonstrates that birds, non-avian archosauromorphs, and lepidosaurs possess significantly different canal morphologies, and represents the first morphometric analysis of semicircular canals across Diapsida.Palaeoneurology, the study of the brain in the fossil record and how it has changed through time 1 , provides some of the best evidence for how extinct animals behaved and interacted with their environment. The behaviour and sensory abilities of extinct taxa are inferred based on the morphology of regions of the brain that are directly responsible for processing sensory information and forming behaviour. Other neural structures are often included in palaeoneurological studies, such as the cranial nerves and membranous labyrinth, which transmit sensory and motor information to and from the brain, and facilitate the sensation of movement and orientation, respectively. Estimations of sensory ability and behaviour based on the morphology of the brain are made possible by the principle of proper mass, which states that the size of a brain region dedicated to a specific function is directly correlated with the amount of processing power required to complete that function 2 . Therefore, regions of the brain that require more processing power tend to be larger to accommodate a greater number of neurons.This correlation allows hypotheses to be made about the sensory ability of extinct animals based on the morphology of the brain; 3,4 however, the brain endocast is not a perfect reflection of the brain in life, as it also represents other soft-tissue structures housed within the endocranial cavity that did not fossilize, such as the dura matter and vascular tissue 5 . Despite this, a description of the endocranial cavity of an extinct animal provides data that can be used to infer its neurosensory capabilities by comparison to closely related extant taxa, which allows for the formation o...

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mentioning

confidence: 99%

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

Dudgeon

Maddin

Evans

et al. 2020

Sci Rep

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“…1 µPa at 100 Hz) than H. stokesii or other snakes previously tested (Martin et al, 2012). Wever (1978) found measured cochlear potentials in response to airborne sounds in the sea snake Hydrophis ( previously Pelamis) platurus and measured responses over a range from 30 to 5000 Hz, with the highest sensitivity below 100 Hz, but poor sensitivity overall compared with other snakes. The terrestrial snake P. regius showed highest sensitivity to sound stimuli from 80 to 160 Hz at 78 dB re.…”

Section: Resultsmentioning

confidence: 92%

“…Because it lacks a tympanic middle ear, the terrestrial snake auditory system is thought to respond mostly to low-frequency sound and vibrations from the substrate (Hartline and Campbell, 1969;Wever, 1978). Vibrations are conducted through the snake's jawbone, relaying a signal to the brain via the inner ear (Christensen et al, 2011;Wever, 1978). Underwater, vibrations at a similar magnitude from a moving object in the water column, or directly transmitted through the substrate, could elicit a 'hearing' response from the inner ear.…”

Section: Resultsmentioning

confidence: 99%

“…Snakes lack both an external ear and a tympanic middle ear and thus are thought to have a reduced sensitivity to airborne sound compared with other tetrapods (Hartline and Campbell, 1969;Wever, 1978). Christensen et al (2011) showed that the terrestrial royal python (Python regius) responded to low-frequency (80-160 Hz) vibration of the substrate, rather than airborne pressure variations, and suggested that all snakes may have lost pressure-transduced hearing and instead use vibration sensitivity for communication and detection of predators and prey (Hetherington, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Underwater hearing in sea snakes (Hydrophiinae): first evidence of auditory evoked potential thresholds

Chapuis

Kerr

Collin

et al. 2019

Journal of Experimental Biology

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The viviparous sea snakes (Hydrophiinae) are a secondarily aquatic radiation of more than 60 species that possess many phenotypic adaptations to marine life. However, virtually nothing is known of the role and sensitivity of hearing in sea snakes. This study investigated the hearing sensitivity of the fully marine sea snake Hydrophis stokesii by measuring auditory evoked potential (AEP) audiograms for two individuals. AEPs were recorded from 40 Hz (the lowest frequency tested) up to 600 Hz, with a peak in sensitivity identified at 60 Hz (163.5 dB re. 1 µPa or 123 dB re. 1 µm s −2 ). Our data suggest that sea snakes are sensitive to low-frequency sounds but have relatively low sensitivity compared with bony fishes and marine turtles. Additional studies are required to understand the role of sound in sea snake life history and further assess these species' vulnerability to anthropogenic noise.

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“…The other two-thirds cover frequencies N1 kHz [98], and this part is demarcated by a change in the organization of the papilla, which is split longitudinally into two parallel sections with distinct tectorial coats. Hair cells located near the neural limb are overlain with a continuous tectorial curtain, whereas abneural hair cells are topped by discrete tectorial domes known as sallets [99][100][101] (Figure 6A). The two parallel strips also differ in their innervation.…”

Section: Lizardsmentioning

confidence: 99%

Diverse Mechanisms of Sound Frequency Discrimination in the Vertebrate Cochlea

Fettiplace

2020

Trends in Neurosciences

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Discrimination of different sound frequencies is pivotal to recognizing and localizing friend and foe. Here, I review the various hair cell-tuning mechanisms used among vertebrates. Electrical resonance, filtering of the receptor potential by voltage-dependent ion channels, is ubiquitous in all non-mammals, but has an upper limit of~1 kHz. The frequency range is extended by mechanical resonance of the hair bundles in frogs and lizards, but may need active hair-bundle motion to achieve sharp tuning up to 5 kHz. Tuning in mammals uses somatic motility of outer hair cells, underpinned by the membrane protein prestin, to expand the frequency range. The bird cochlea may also use prestin at high frequencies, but hair cells b1 kHz show electrical resonance. Hair Cell-Tuning Mechanisms and Cochlear Structure Hair cells, the sensory receptors of the vertebrate inner ear, convert sound stimuli into electrical signals, and also separate the frequency constituents of the sound, enabling different subsets of hair cells to encode different frequencies. To ensure survival, an animal uses its auditory apparatus to both identify the sound source, whether friend, food, or foe, and to spatially localize it. Are the cries within the forest at night those of an offspring or a predator? Crucially, from which direction do they originate? Can you recognize the voice of a friend across a dark room at a crowded party? Accurate classification and localization of sounds depend on their frequency make-up [1,2]. The mechanisms involved in frequency discrimination differ between the vertebrate classes (reptile, bird, or mammal) and importantly depend on the tonal range to be detected. During the evolution of land vertebrates, there was a drive to extend the upper frequency limit of hearing from a few hundred Hz in the simplest amphibians or reptiles up to~100 kHz in small mammals. To this end, changes have occurred in sound transmission through the middle ear, in the structure of the cochlea, and in the roles of the hair cells. The reasons for the frequency extension are not known for certain. They may partly derive from selective pressure for localizing sounds in animals with small heads, such as the first mammals, or in finding tiny offspring from their high-frequency cries. Another factor driving frequency extension is communication between species members, exemplified by the croaks of frogs, the chirps of geckos, and bird songs, which are all comprise kilohertz sound frequencies. In this review, I describe the evidence for the different cochlear mechanisms, all of which depend upon resonant behavior. A simple illustration of resonance is that generated by a mass, M, suspended on the end of a spring of stiffness K: when the mass is displaced, it oscillates with a resonant frequency, F O, equal to 1//2π.(K/M) 1/2 , and F O increases with larger stiffness and smaller mass. Resonance refers to the increase in the amplitude of the oscillation if an external force is applied at the resonant frequency (but not if the external force is applied at ...

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The Reptile Ear

Cited by 101 publications

References 0 publications

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

The internal cranial anatomy of Champsosaurus (Choristodera: Champsosauridae): Implications for neurosensory function

Underwater hearing in sea snakes (Hydrophiinae): first evidence of auditory evoked potential thresholds

Diverse Mechanisms of Sound Frequency Discrimination in the Vertebrate Cochlea

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