BSP-8-8 Sun Jan 3 18:30 – 18:45 Directional hearing in salamanders Capshaw, G*; Soares, D; Christensen-Dalsgaard, J; Carr, CE; University of Maryland, College Park; New Jersey Institute of Technology; University of Southern Denmark, Odense; University of Maryland, College Park email@example.com
The evolution of the vertebrate auditory system, prior to the development of acoustic communication, was driven to enhance the detection of biologically relevant sounds within the environment and to associate them with their source in order to construct an auditory scene of their surroundings. The ability to localize sounds confers a clear fitness advantage for species that can use acoustic cues to facilitate navigation within a complex environment, detect prey, and avoid predators. In many terrestrial species, the tympanic middle ear is a key sensory feature enabling the encoding of directional cues from sound sources; however, fossil evidence reveals a delay between the water-to-land transition and the emergence of tympanic middle ears during which the ancestral tetrapod ear was largely unspecialized for terrestrial hearing. Inherently directional otolithic ears emerged early in vertebrate evolutionary history, however, indicating that peripheral encoding of directional acoustic cues may be an ancestral feature of the tetrapod auditory system. Here, we used atympanic salamanders to test the hypothesis that extratympanic mechanisms for hearing are sufficient to confer directionality in a terrestrial environment. We performed auditory brainstem response recordings to investigate the peripheral encoding of directional information in the auditory nerve from free-field sound pressure stimuli. We combined these measurements with laser vibrometry to assess the contributions of bone conduction mechanisms for directional hearing in these atympanic species.