Pigment cell organization in the hypodermis of zebrafish.

Zebrafish have a characteristic horizontal-stripe pigment pattern made by a specific distribution of three types of pigment cells: melanophores, xanthophores, and iridophores. This pattern is a valuable model to investigate how the spatial patterns form during animal development. Although recent findings suggest that the interactions among the pigment cells play a key role, the particular details of these interactions have not yet been clarified. In this report, we performed transmission electron microscopic study to show the distribution, conformation, and how the cells contact with each other in the hypodermis. We found that the pigment cells form complex but ordered, layered structures in both stripe and interstripe regions. The order of the layered structures is kept strictly all through the hypodermal regions. Our study will provide basic information to investigate the mechanism of pigment pattern formation in zebrafish.