Effect of PrRP treatment on the thickness of cellular layers on the goldfish scales. The mucous cell layer in PrRP-treated fish (A) was thicker than in control (B) fish. Anti-PrRP treatment induced no consistent results (C). Arrows on the left side of each photographs shows the mucous cell layers. The scale bar represents 50 um. (b) Frequency histogram of the mucous cell layer thickness. The percentage of the cell layer thickness to the scale (dermal bone) thickness was analyzed (two fishes for each treatment, five scales from each fish and five trials on each scale). The distribution peak of the PrRP-treated fish apparently inclined toward the right side (much thicker part) compared with those of control and anti-PrRP-treated fish.