Mahurin Honors College Capstone Experience/Thesis Projects



Document Type



Melanin is the dark pigment responsible for influencing the color of bodily structures, and it is variably present throughout human and animal tissue. Melanin is also found within the mammalian inner ear, and it has been observed that a lack of melanin is associated with greater susceptibility to sensorineural hearing loss. In this study, melanin levels of the inner ears of different color morphs of the fish species Poecilia latipinna and Cyprinus carpio were measured and the potential protective role of that melanin from acoustical stress was examined. Previous research showed that black morphs of both species exhibited less noise-induced hearing loss than white morphs, but it was unknown if this was due to the loss of fewer auditory hair cells in morphs with more melanin. We hypothesized that black color morphs would have more melanin in the inner ear and exhibit less noise-induced auditory sensory hair cell loss compared to white color morphs. Both ears were extracted from specimens of each species, and melanin levels were quantified using a spectrophotometric assay. Black morphs had significantly higher melanin levels within the inner ear in comparison to white morphs. Both morphs of P. latipinna were exposed to an acoustical stimulus for 48 hours and their inner ears were then dissected, labeled with phalloidin, and imaged under epifluorescence microscopy. The density of saccular auditory hair cells was quantified and compared between noise- exposed fishes and controls and between black and white fishes within each treatment. Although noise-exposed fishes exhibited significant hair cell loss compared to controls as expected, there were no significant differences in noise-induced hair cell bundle loss between the two morphs. This suggests that melanin does not play a role in conserving hair cell bundle density, but rather may be conserving the integrity of the surviving hair cells in the teleost inner ear. Future research is needed to understand the cellular mechanisms in which melanin may provide this auditory protection and may pave the way for new otoprotective drug testing opportunities.

Advisor(s) or Committee Chair

Michael Smith, Ph.D.


Neuroscience and Neurobiology | Other Neuroscience and Neurobiology | Physiology | Zoology

Available for download on Friday, June 26, 2026