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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Hearing Sensitivity and the Effect of Sound Exposure on the Axolotl (Ambystoma Mexicanum)

Fehrenbach, Amy K. 01 May 2015 (has links)
The axolotl (Ambystoma mexicanum) has been used as a model organism for studying development, genetics, and regeneration. Although the sensory hair cells of the lateral line of this species have been shown to be able to regenerate, it is not known whether this also occurs in the inner ear. In fact, little is known about the hearing capabilities of the axolotl or other salamander species. I recorded auditory evoked potentials (AEPs) of six axolotls at eleven frequencies (0.1, 0.25, 0.4, 0.6, 0.8, 1, 1.5, 2, 3, 4, and 6 kHz) in order to produce baseline audiograms of underwater pressure sensitivity. Individuals were then subjected to a 48-hour, 150 Hz sound exposure at approximately 170 dB (re 1 μPa). AEPs were then performed to measure hearing thresholds immediately after sound exposure and at 2, 4, and 8 days post-sound exposure (DPSE). In the baseline audiogram, axolotls were most sensitive at 600 Hz, with an additional peak of sensitivity at 3 kHz. Following sound exposure, axolotls experienced a 6 to 12 dB temporary threshold shift (TTS) after sound exposure, with TTS being greatest at low frequencies near the 150 Hz stimulus frequency (i.e., 100 and 250 Hz). Hearing sensitivity returned to control levels within 8 DPSE. This indicates that axolotls do possess the ability to recover hearing sensitivity after damage following acoustical trauma. This study is the first to document hearing loss in the axolotl. Future studies are needed to correlate this hearing loss and recovery to sensory hair cell loss and regeneration in the axolotl inner ear.

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