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Published on: October 17, 2012
Sound transmission in the salamander ear
Summary
Amphibian hearing differs across orders, with salamanders exhibiting unique binaural sound stimulation. Vibrations travel through the brain cavity to both ears, engaging auditory organs for a complete auditory experience.
Area of Science:
- Comparative physiology
- Auditory system evolution
- Amphibian biology
Background:
- The mechanism of sound perception in Amphibia varies among extant orders.
- The auditory system's structure and function are key to understanding amphibian sensory ecology.
Purpose of the Study:
- To investigate the distinct modes of auditory stimulation in Amphibia.
- To elucidate the unique sound conduction pathway in the order Caudata.
Main Methods:
- Analysis of sound vibration pathways in the amphibian auditory system.
- Comparative study across different amphibian orders, focusing on Caudata.
Main Results:
- Auditory stimulation in Amphibia presents order-specific variations.
- Caudata (salamanders) demonstrate a unique sound transmission: vibrations applied to one oval window travel through the brain cavity to the contralateral oval window.
- This pathway involves both the amphibian papillae and basilar papillae (when present), ensuring binaural hearing in salamanders.
Conclusions:
- Salamanders possess an invariably binaural auditory system due to their unique sound conduction mechanism.
- The findings highlight specialized auditory adaptations within Amphibia, particularly in the Caudata order.
Related Concept Videos
Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
The Auditory Ossicles
The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. The auditory ossicles consist of two malleus (hammer) bones, two incus (anvil) bones, and two stapes (stirrups), one on each side. These bones develop during the fetal stage and are the ones to ossify first. They are fully mature at birth and do not grow afterward.
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
Echo
The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources.
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
Anatomy of the Ear
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...
Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...

