Iwata Masaki, Otaki Joji M
The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-0213, Japan; Department of International Agricultural Development, Faculty of International Agriculture and Food Studies, Tokyo University of Agriculture, Sakuragaoka, Setagaya, Tokyo 156-8502, Japan.
The BCPH Unit of Molecular Physiology, Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru, Nishihara, Okinawa 903-0213, Japan.
J Insect Physiol. 2019 Apr;114:68-82. doi: 10.1016/j.jinsphys.2019.02.009. Epub 2019 Feb 21.
Butterfly eyespot color patterns are traditionally explained by the gradient model, where positional information is stably provided by a morphogen gradient from a single organizer and its output is a set of non-graded (or graded) colors based on pre-determined threshold levels. An alternative model is the induction model, in which the outer black ring and the inner black core disk of an eyespot are specified by graded signals from the primary and secondary organizers that also involve lateral induction. To examine the feasibility of these models, we analyzed eyespot color gradients, boundary scales, and rudimentary eyespots in various nymphalid butterflies. Most parts of eyespots showed color gradients with gradual or fluctuating changes with sharp boundaries in many species, but some species had eyespots that were composed of a constant color within a given part. Thus, a plausible model should be flexible enough to incorporate this diversity. Some boundary scales appeared to have two kinds of pigments, and others had "misplaced" colors, suggesting an overlapping of two signals and a difficulty in assuming sharp threshold boundaries. Rudimentary eyespots of three Junonia species revealed that the outer black ring is likely determined first and the inner yellow or red ring is laterally induced. This outside-to-inside determination together with the lateral induction may favor the induction model, in which dynamic signal interactions play a major role. The implications of these results for the ploidy hypothesis and color-pattern rules are discussed.
传统上，蝴蝶眼斑颜色模式是由梯度模型来解释的，在该模型中，形态发生素梯度从单个组织者稳定地提供位置信息，其输出是基于预定阈值水平的一组非分级（或分级）颜色。另一种模型是诱导模型，其中眼斑的外部黑环和内部黑核盘由来自初级和次级组织者的分级信号指定，这也涉及侧向诱导。为了检验这些模型的可行性，我们分析了各种蛱蝶科蝴蝶的眼斑颜色梯度、边界尺度和雏形眼斑。在许多物种中，眼斑的大部分区域呈现出颜色梯度，有逐渐变化或波动变化且边界清晰，但有些物种的眼斑在给定部分内由单一颜色组成。因此，一个合理的模型应该足够灵活以纳入这种多样性。一些边界尺度似乎有两种色素沉着，而其他的则有“错位”颜色，这表明两种信号存在重叠，且难以假设有清晰的阈值边界。三种眼蝶属物种的雏形眼斑表明，外部黑环可能首先被确定，内部黄色或红色环是通过侧向诱导形成的。这种从外到内的确定方式以及侧向诱导可能更支持诱导模型，在该模型中动态信号相互作用起主要作用。我们还讨论了这些结果对倍性假说和颜色模式规则的影响。
