Meeting Abstract
How does an animal perceive sound without ears? The tympanic middle ear is a key sensory innovation that emerged several times in vertebrate evolutionary history as early tetrapods transitioned from aquatic to terrestrial lifestyles. This structure is typically comprised of a tympanic membrane connected to the oval window of the inner ear via one to three ossicles in an air-filled middle ear cavity, and it functions as a transducer of airborne sound pressure into fluid movement in the inner ear. However, several terrestrial vertebrate species including “earless” frogs, snakes, and salamanders have lost their tympanum and middle ear cavity. We used salamanders as a model to test the role of several proposed extratympanic pathways for sound and vibration detection including bone conduction, the amphibian opercularis system, and the air-filled lungs. We compared auditory sensitivity in lungless salamander species against those that retain lungs, and found that lungs are not necessary for terrestrial hearing in atympanic species. Bone conduction is sufficient for detection of low frequency sound and vibration.
