FIG. 1.

Progression of melanocyte morphology during exposure to NCP. (A) An untreated, fully pigmented fish. (B) A fish after 10 days of NCP treatment. It is almost entirely devoid of melanin in the body stripes and fins. (C–J) Close-ups of melanocyte stripes after treatment with NCP. Melanosomes are fully relaxed, and there are many pigmented processes before treatment with NCP (C). After 3 days, the melanin has contracted to result in lobular melanin masses (D, arrows). Some melanocytes have begun to fragment (D, arrowheads). After 5 days of NCP, melanin appears as if acellular (E). After 7 days, most of the melanin has been cleared, leaving scattered granules (F). Fish untreated with NCP prior (G) and after exposure (H) to epinephrine. Note the contracted melanosomes in (H) compared to (G) and that these contracted melanosomes are regular and round in appearance. Lobular melanin masses after 3 days in NCP look similar before (I) and after exposure (J) to epinephrine. Asterisks in (I) and (J) mark the same melanocytes. Note that there is no change in these melanocytes after epinephrine treatment. Scale bars in (A, B) are 1 mm and in (C–J) are 100 μm.