Young zebrafish have more inner ear hair cells. (a) Representative confocal images of inner ear epithelia from young (top row) and old (bottom row) adult zebrafish. The scale bar in the top left image applies to all images. (b) Quantification of phalloidin-labeled hair bundles from young (green bars) and old (gray bars) zebrafish epithelia. Hair bundles were counted in three 50 X 50 µm regions of interest (ROI) per epithelium for the saccule and utricle and two 50 X 50 µm ROI for the lagena. Graphs show hair bundle quantification for each epithelium separated by ROI. There is a significant main effect of age for each epithelium. Saccule, F1,85 = 8.593; p = 0.0043; utricle F1,84 = 11.89, p = 0.0009; lagena F1,56 = 15.68, p = 0.0002. There is no significant age-by-region interaction for any epithelium (saccule, F2,84 = 1.08, p = 0.344; utricle F2,84 = 1.98, p = 0.144; lagena F1,56 = 0.09, p = 0.770). Bonferroni-corrected post-hoc tests, *p < 0.05, **p < 0.01. Data are presented as mean ± 1 s.d. and dots represent individual fish. N = 16 young fish, n = 14 old fish.
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