Preexposure to acidic water increases the number of Sodium Green-positive cells that are not HRCs. A–C: at 4 days postfertilization, accumulation of Sodium Green was predominantly confined to HRCs (labeled by concanavalin A) in the skin of larval zebrafish following exposure to control water (pH 7.6). D–F: after preexposure to acidic water (pH 4.0), accumulation of Sodium Green was observed in epithelial cells that were not HRCs. Scale bar = 25 μm. Quantitative analysis revealed that the total number of Sodium Green-positive cells (G) and the numbers of Sodium Green-positive non-HRCs (H) were significantly increased after acid exposure. I: however, acid exposure did not affect the number of Sodium Green-positive HRCs. Values are means ± SE. *Statistical difference between groups (Student's t-test, N = 6), P < 0.05.