Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia.
Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia.
Evol Dev. 2019 Jan;21(1):3-15. doi: 10.1111/ede.12272. Epub 2018 Sep 21.
The Mesoamerican cichlids display a spectacular diversity of pigment patterns, which serve a variety of functions and serve as a strong selective trait for this lineage. The development and variation of coloration in the Mesoamerican cichlids have been detailed by several groups. In particular, Říčan, Musilová, Muška, and Novák () and Říčan, Piálek, Dragová, and Novák () determined homology of pattern and revealed four alternative types of coloration and their ontogeny. In this work, this group posed an "ontogenetic timing hypothesis" proposing heterochronic shifts underlying major transitions in the evolution of the Mesoamerican cichlids. Here, we experimentally test this hypothesis by experimentally altering timing of pigment pattern formation in the convict cichlid Amatitlania nigrofasciata, a member of the Mesoamerican cichlids, via manipulations of thyroid hormone (TH) function. The response of different pigment cell lineages to TH-perturbations revealed that the transition from larval to juvenile coloration in the convict cichlid is under the control of TH-signaling. Importantly, hormonally induced changes in the timing of pigment cell lineages' development resulted in shifts of coloration ontogeny type observed between lineages and led to the appearance of phenotypes mimicking those in phylogenetically close and distant species. Thus, our findings support the hypothesis that simple changes in ontogenetic timing underlies species specific patterns in pigmentation and provide new perspectives for studying the role of endocrine signaling in the evolution of cichlids.
中美洲慈鲷展示出丰富多彩的色素模式，这些模式具有多种功能，并成为该谱系的一个强烈的选择性特征。中美洲慈鲷的颜色发育和变化已经被多个研究小组详细研究。特别是，Říčan、Musilová、Muška 和 Novák () 和 Říčan、Piálek、Dragová 和 Novák () 确定了图案的同源性，并揭示了四种替代类型的颜色及其个体发生。在这项工作中，该小组提出了一个“个体发生时间假说”，提出了中美洲慈鲷进化中主要转变背后的异时性转变。在这里，我们通过实验改变甲状腺激素 (TH) 功能来改变中美洲慈鲷的代表物种——黑带副丽鱼的色素模式形成的时间，从而实验测试了这个假说。不同色素细胞谱系对 TH 扰动的反应表明，黑带副丽鱼从幼虫到幼鱼颜色的转变受 TH 信号的控制。重要的是，色素细胞谱系发育时间的激素诱导变化导致观察到的谱系间颜色发生类型的转变，并导致出现模仿近缘和远缘物种表型的表型。因此，我们的发现支持了这样的假设，即个体发生时间的简单变化是色素形成中物种特异性模式的基础，并为研究内分泌信号在慈鲷进化中的作用提供了新的视角。
