Active control of ultrasonic hearing in frogs
- 5 August 2008
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 105 (31), 11014-11019
- https://doi.org/10.1073/pnas.0802210105
Abstract
Vertebrates can modulate the sound levels entering their inner ears in the face of intense external sound or during their own vocalizations. Middle ear muscle contractions restrain the motion of the middle ear ossicles, attenuating the transmission of low-frequency sound and thereby protecting the hair cells in the inner ear. Here we show that the Chinese concave-eared torrent frog, Odorrana tormota, can tune its ears dynamically by closing its normally open Eustachian tubes. Contrary to the belief that the middle ear in frogs permanently communicates with the mouth, O. tormota can close this connection by contraction of the submaxillary and petrohyoid muscles, drastically reducing the air volume behind the eardrums. Mathematical modeling and laser Doppler vibrometry revealed that the reduction of this air volume increases the middle ear impedance, resulting in an up to 20 dB gain in eardrum vibration at high frequencies (10-32 kHz) and 26 dB attenuation at low frequencies (3-10 kHz). Eustachian tube closure was observed in the field during calling and swallowing. Besides a potential role in protecting the inner ear from intense low-frequency sound and high buccal air pressure during calling, this previously unrecognized vertebrate mechanism may unmask the high-frequency calls of this species from the low-frequency stream noise which dominates the environment. This mechanism also protects the thin tympanic membranes from injury during swallowing of live arthropod prey.Keywords
This publication has 22 references indexed in Scilit:
- Ultrasonic frogs show hyperacute phonotaxis to female courtship callsNature, 2008
- Rearrangement of a mitochondrial tRNA gene of the concave-eared torrent frog, Amolops tormotusGene, 2007
- Ultrasonic communication in frogsNature, 2006
- Comparative studies of the biophysics of directional hearing in anuransJournal of Comparative Physiology A, 1991
- The Middle-Ear MusclesScientific American, 1989
- Theories of Middle-Ear Muscle FunctionPublished by Elsevier BV ,1984
- Hearing in the frog: dynamics of the middle earProceedings of the Royal Society of London. B. Biological Sciences, 1981
- Directional hearing in the green treefrog: A variable mechanism?The Science of Nature, 1981
- Tympanic muscle effects on middle-ear transfer characteristicThe Journal of the Acoustical Society of America, 1974
- A Quantitative Study of the Effect of the Acoustic Stapedius Reflex on Sound transmission Through the Middle Ear of ManActa Oto-Laryngologica, 1968