Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye.
Pigmented anatomy in Carboniferous cyclostomes and the evolution of the vertebrate eye.
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DOI：
10.1098/rspb.2016.1151
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发表时间：
2016-08-17
期刊：
影响因子：
--
通讯作者：
Purnell MA
中科院分区：
文献类型：
--
作者：
Gabbott SE;Donoghue PC;Sansom RS;Vinther J;Dolocan A;Purnell MA
脊椎动物的成功与相机式眼睛和复杂视觉系统的进化有关。由于缺乏来自化石的有用数据，脊椎动物眼睛进化组装的场景必须基于活脊椎动物发育，分子遗传学和比较解剖学的证据。不幸的是，从无脊椎脊索动物的感光“眼斑”过渡到有颌脊椎动物的成像相机式眼睛的步骤仅受到八目鳗和七鳃鳗（圆口目）的限制，这被解释为反映了中间或退化的条件。在这里，我们报告的基础上的证据的大小，形状，保存模式和本地化的发生-黑色素体（色素轴承细胞器）在化石圆口动物眼睛的存在。飞行时间二次离子质谱分析揭示了具有黑色素的相对强度特征的二次离子，如通过主成分分析所揭示的。我们的数据支持的假设，即现存的八目盲鳗的眼睛是退化的，而不是基本的，圆口类是单系的，和祖先的脊椎动物有一个功能性的视觉系统。我们还展示了化石七鳃鳗的外皮色素沉着，打开了令人兴奋的可能性，调查古生代脊椎动物的颜色图案。我们报告的例子增加了石炭纪化石中黑素体保存的记录，并证明了黑素体和生物分子黑素惊人的耐久性。
The success of vertebrates is linked to the evolution of a camera-style eye and sophisticated visual system. In the absence of useful data from fossils, scenarios for evolutionary assembly of the vertebrate eye have been based necessarily on evidence from development, molecular genetics and comparative anatomy in living vertebrates. Unfortunately, steps in the transition from a light-sensitive ‘eye spot’ in invertebrate chordates to an image-forming camera-style eye in jawed vertebrates are constrained only by hagfish and lampreys (cyclostomes), which are interpreted to reflect either an intermediate or degenerate condition. Here, we report—based on evidence of size, shape, preservation mode and localized occurrence—the presence of melanosomes (pigment-bearing organelles) in fossil cyclostome eyes. Time of flight secondary ion mass spectrometry analyses reveal secondary ions with a relative intensity characteristic of melanin as revealed through principal components analyses. Our data support the hypotheses that extant hagfish eyes are degenerate, not rudimentary, that cyclostomes are monophyletic, and that the ancestral vertebrate had a functional visual system. We also demonstrate integument pigmentation in fossil lampreys, opening up the exciting possibility of investigating colour patterning in Palaeozoic vertebrates. The examples we report add to the record of melanosome preservation in Carboniferous fossils and attest to surprising durability of melanosomes and biomolecular melanin.
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