[Investigations on the colour pattern of the zebra fishBrachydanio rerio (Cyprinidae, teleostei)].

1. The genetics of some colour breeds was investigated. One gene is responsible for the degree of pigmentation of the melanophores (normal pigmentation versus slight pigmentation); another one controls the arrangement of the pigment cells (longitudinal stripes-spot pattern respectively); and a third one regulates the destruction of all the xanthophores and some of the iridophores and melanophores. 2. The melanophores of the longitudinal stripes and those of the spots lie in the uppermost subcutaneous layer. More melanophores were found in the epidermis above and below the scales; with others making direct contact with the scales or occurring in the loose dermis within the scale pockets. 3. The ontogenetic sequence of pattern formation in the phenotypesre, fr andgr was investigated. 4. The reduced pigmentation of melanophores of the light formmlr could not be explained by a lack of chromogen (Dopa) but was found to be based upon the intrinsic formation of numerous intermediary weakly pigmented "melanosome" within these cells. 5. A phenocopy of themlr type could be obtained by treatment with phenylthiourea (0.002-0.004%). 6. Factors within the subcutis were proved responsible for the formation of the melanophore stripes. The stability of these factors was demonstrated by auto- and isotransplantation. 7. Melanoblasts could be found in the xanthophore stripes of the anal fin of the wild form. 8. The number of xanthophores in the anal fin of the phenotypesre andmlr is nearly twice as high as that of the phenotypefr. ♂♂ and ♀♀ always show the same number of xanthophores. 9. In the xanthophores offr-animals melanosome-like structures were found which do not occur in there-phenotypes.