Frost S K, Epp L G, Robinson S J
J Embryol Exp Morphol. 1984 Jun;81:127-42.
The melanoid mutant in the Mexican axolotl (Ambystoma mexicanum) is analysed with respect to the differentiation of pigment cells. Pigment cells were observed with the transmission electron microscope in order to determine any unusual structural characteristics and to determine what happens to each of the cell types as development proceeds. Chemical analysis of pteridine pigments was also carried out, and changes in pteridine biosynthesis were found to correlate well with changes in xanthophore morphology and number. In melanoid axolotls, as development proceeds, melanophore numbers increase, xanthophores decrease, and iridophores fail to differentiate at all. This is considered to result from: (a) conversion of xanthophores (that are present in young larvae) to melanophores; (b) the gradual programming of the majority of chromatoblasts to become, exclusively, melanophores, and (c) the failure of some chromatoblasts (possibly iridoblasts) to differentiate altogether. The ultrastructural and chemical evidence presented in this study is compared to similar data for wild-type axolotls, and a mechanism regarding how the melanoid gene might act is suggested.
对墨西哥钝口螈（美西钝口螈）的类黑素突变体进行了色素细胞分化方面的分析。为了确定任何异常的结构特征以及随着发育进程每种细胞类型会发生什么变化，利用透射电子显微镜观察了色素细胞。还对蝶啶色素进行了化学分析，发现蝶啶生物合成的变化与黄色素细胞形态和数量的变化密切相关。在类黑素钝口螈中，随着发育进程，黑素细胞数量增加，黄色素细胞减少，而虹彩细胞根本无法分化。这被认为是由以下原因导致的：(a) 黄色素细胞（存在于幼体幼虫中）转化为黑素细胞；(b) 大多数成色素细胞逐渐被编程，使其仅成为黑素细胞；(c) 一些成色素细胞（可能是成虹彩细胞）完全无法分化。将本研究中呈现的超微结构和化学证据与野生型钝口螈的类似数据进行了比较，并提出了关于类黑素基因可能如何起作用的机制。
