Prolific Origination of Eyes in Cnidaria with Co-option of Non-visual Opsins
Prolific Origination of Eyes in Cnidaria with Co-option of Non-visual Opsins
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DOI：
10.1016/j.cub.2018.05.055
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发表时间：
2018-08-06
期刊：
影响因子：
9.2
通讯作者：
Oakley, Todd H.
中科院分区：
文献类型：
--
作者：
Picciani, Natasha;Kerlin, Jamie R.;Oakley, Todd H.
动物的眼睛在形态和复杂性上有很大的不同，因此是了解复杂生物特征进化的理想之选[1]。虽然眼睛在具有复杂神经系统的双边动物中进化了很多次，但蛇形动物也存在成像和简单的眼睛，这种动物是古老的非双边动物，有神经网络，区域有浓缩的神经元来处理信息。在具有如此简单神经回路的动物身上，包括成像眼睛在内的不同复杂程度的眼睛出现的频率仍然不清楚。在这里，我们制作了蛇床目及其光敏蛋白的大规模系统发育图，并结合对眼睛和光感知行为的广泛文献搜索，表明蛇尾目动物的眼睛至少起源了8次，复杂的晶状体眼睛有一段与其他眼睛类型不同的历史。汇编的数据显示，盲目蜈蚣的感光行为普遍存在，对比分析支持了没有眼睛的祖先已经通过分散的感光细胞感知到光线。光感受性视蛋白表达的历史支持通过不同的非视觉视蛋白类似物单独共选进入眼睛来推测不同的眼睛起源。总体而言，我们的结果表明，在具有简单神经系统的非双边动物中，眼睛重复地从祖先的光感受器细胞进化而来，吸收现有的前体，类似于在比拉特里亚发生的情况。我们的研究强调了多个进化上截然不同的视觉系统的潜力，即使在只有简单神经系统的动物身上也是如此。
Animal eyes vary considerably in morphology and complexity and are thus ideal for understanding the evolution of complex biological traits [1]. While eyes evolved many times in bilaterian animals with elaborate nervous systems, image-forming and simpler eyes also exist in cnidarians, which are ancient non-bilaterians with neural nets and regions with condensed neurons to process information. How often eyes of varying complexity, including image-forming eyes, arose in animals with such simple neural circuitry remains obscure. Here, we produced large-scale phylogenies of Cnidaria and their photosensitive proteins and coupled them with an extensive literature search on eyes and light-sensing behavior to show that cnidarian eyes originated at least eight times, with complex, lensed-eyes having a history separate from other eye types. Compiled data show widespread light-sensing behavior in eyeless cnidarians, and comparative analyses support ancestors without eyes that already sensed light with dispersed photoreceptor cells. The history of expression of photoreceptive opsin proteins supports the inference of distinct eye origins via separate co-option of different non-visual opsin paralogs into eyes. Overall, our results show eyes evolved repeatedly from ancestral photoreceptor cells in non-bilaterian animals with simple nervous systems, co-opting existing precursors, similar to what occurred in Bilateria. Our study underscores the potential for multiple, evolutionarily distinct visual systems even in animals with simple nervous systems.