Hair cells are derived from proliferating progenitors.

<p>(A) Wild type larvae were treated at 5 dpf with neomycin or copper for 1 h followed by recovery in 5 mM BrdU until 24 hpt followed by fresh embryo medium. Greater numbers of BrdU-positive hair cells were observed in all ototoxin-treated groups at 72 hpt. (B) One-way ANOVA followed by a Tukey post-hoc analysis of the proportion of BrdU-positive hair cells revealed significant increases in all ototoxin-treated groups compared to control (<i>p</i><0.001). No significant difference was observed between 1 and 10 μM copper that would suggest a dose-dependent effect on proliferative regeneration. A small but significant difference was observed between neomycin and 1 μM copper (*, <i>p</i><0.05). <i>N</i> = 8 fish per group. Error bars are + SD. (C) Example neuromast at 72 hpt from a fish treated with 1 μM copper. Arrows mark BrdU-positive hair cells.