Meeting Abstract

P1-111  Saturday, Jan. 4  Acoustic reception in salamanders: Skull vibrations enable sound pressure detection CAPSHAW, G*; SOARES, D; CHRISTENSEN-DALSGAARD, J; CARR, CE; University of Maryland, College Park; New Jersey Institute of Technology; University of Southern Denmark; University of Maryland, College Park gcapshaw@umd.edu

The evolution of a tympanic middle ear was a crucial sensory innovation that enabled terrestrial tetrapods to transduce airborne sound into fluid movement in the inner ear. Without a tympanic middle ear, airborne sound energy is expected to reflect off of the air-skin boundary, and atympanic species such as salamanders have long been considered functionally deaf in terrestrial environments. We measured the auditory sensitivity of salamanders to airborne sound pressure and seismic vibration using auditory brainstem response recording. We assessed several proposed extratympanic pathways for acoustic transmission to the inner ear, including via inertial bone conduction, and the mouth- and lung-ear routes. The resonant capacity of the air-filled mouth and lungs of the tested species had little influence on the range and threshold sensitivity of the ear. We used laser vibrometry to measure sound-induced vibrations in the skull and the substrate and compared our results to a model for sound translation of the skull. We found that threshold level sound pressure-induced vibrations of the skull are sufficient to stimulate the auditory end organs, and likely represent a key mechanism for terrestrial hearing in salamanders.