Two developmental stages of dark pigmentation were visually observed in koi—one
around hatching and the second around 14-day post-hatching. Hatched-out larvae with
dark pigmentation only around 14 days of age developed a Bekko pattern. This implies
that accumulation of the melanin pigment in melanocytes is, at least in part, controlled by
different genes for the Bekko and Utsuri patterns. In this sense, we find our results similar
to what is known in zebrafish where two populations of melanocytes with different
developmental onsets are associated with different color phenotypes and controlled in part
by different genes (