Using Zebrafish to Investigate the Effects of Triclosan on Hearing Development
Moran, Kelsey N.
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Humans and wildlife are exposed to many thyroid disrupting chemicals which can interfere with the thyroid hormone system. Thyroid hormones are critical to the development of the brain and auditory system. Thus, thyroid hormone disrupting chemicals (THDC) could affect the development of the brain and hearing. A common THDC is triclosan, a chemical that is currently being used in personal care products. The aim of this study was to initiate experiments with zebrafish (Danio rerio) as a model system to investigate the effects of thyroid hormone disrupting chemicals on hearing development. Specifically, our objectives were: to investigate hearing development in zebrafish using the acoustic startle response test; to investigate if thyroid hormone is necessary for the development of hearing in zebrafish; and to investigate the effects of triclosan on hearing development. We used an acoustic startle response test to determine hearing thresholds for zebrafish of different ages and found that there was no significant difference between the percent response and sound pressure level at any age. We assumed that thyroid hormone is necessary for development of zebrafish, and exposed larval fish to doses of triclosan. We found that triclosan did not have any effect on 50 days post fertilization (dpf) but did result in high mortality rates of 9 dpf. Of the remaining 9 dpf fish exposed to triclosan, there was no response at any stimulus emitted, indicating triclosan does effect young larval zebrafish. We concluded that thyroid hormone is necessary for zebrafish development, although more research is needed to further the investigation.