Zebrafish, an auditory specialist among fish, offer analogous auditory structures to vertebrates and is a model for hearing and deafness in vertebrates, including humans. Nevertheless, many questions remain on the basic mechanics of the auditory pathway. Phase-sensitive Optical Coherence Tomography has been proven as valuable technique for functional vibrometric measurements in the murine ear. Such measurements are key to building a complete understanding of auditory mechanics. The application of such techniques in the zebrafish is impeded by the high level of pigmentation, which develops superior to the transverse plane and envelops the auditory system superficially. A zebrafish double mutant for nacre and roy (mitfa-/- ;roya-/- [casper]), which exhibits defects for neural-crest derived melanocytes and iridophores, at all stages of development, is pursued to improve image quality and sensitivity for functional imaging. So far our investigations with the casper mutants have enabled the identification of the specialized hearing organs, fluid-filled canal connecting the ears, and sub-structures of the semicircular canals. In our previous work with wild-type zebrafish, we were only able to identify and observe stimulated vibration of the largest structures, specifically the anterior swim bladder and tripus ossicle, even among small, larval specimen, with fully developed inner ears. In conclusion, this genetic mutant will enable the study of the dynamics of the zebrafish ear from the early larval stages all the way into adulthood.
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