Almost all animals can sense light, but only those with spatial vision can "see." Conventionally, this was restricted to animals possessing discrete visual organs (eyes), but extraocular vision could facilitate vision without eyes. Echinoderms form the focus of extraocular vision research [1-7], and the brittle star Ophiocoma wendtii, which exhibits light-responsive color change and shelter seeking, became a key species of interest [4, 8, 9]. Both O. wendtii and an apparently light-indifferent congeneric, O. pumila, possess an extensive network of r-opsin-reactive cells, but its function remains unclear [4]. We show that, although both species are strongly light averse, O. wendtii orients to stimuli necessitating spatial vision for detection, but O. pumila does not. However, O. wendtii's response disappears when chromatophores are contracted within the skeleton. Combining immunohistochemistry, histology, and synchrotron microtomography, we reconstructed models of photoreceptors in situ and extracted estimated angular apertures for O. wendtii and O. pumila. Angular sensitivity estimates, derived from these models, support the hypothesis that chromatophores constitute a screening mechanism in O. wendtii, providing sufficient resolving power to detect the stimuli. RNA sequencing (RNA-seq) identified opsin candidates in both species, including multiple r-opsins and transduction pathway constituents, congruent with immunohistochemistry and studies of other echinoderms [10, 11]. Finally, we note that differing body postures between the two species during experiments may reflect aspect of signal integration. This represents one of the most detailed mechanisms for extraocular vision yet proposed and draws interesting parallels with the only other confirmed extraocular visual system, that of some sea urchins, which also possess chromatophores [1].

中文翻译：

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脆性恒星中的眼外视力是由响应环境光的染色体运动调节的。

几乎所有的动物都可以感知光线，但是只有具有空间视觉的动物才能“看到”。按照惯例，这仅限于具有离散视觉器官（眼睛）的动物，但是眼外视觉可以促进没有眼睛的视觉。棘皮动物成为眼外视觉研究的重点[1-7]，而表现出光响应性颜色变化和寻找庇护所的脆性星星眼线虫（Ophiocoma wendtii）成为人们关注的重要物种[4、8、9]。温德氏菌和表面上无光的同类物普米氏菌均具有广泛的r-视蛋白反应性细胞网络，但其功能尚不清楚[4]。我们表明，尽管两个物种都强烈厌恶光，但O. wendtii倾向于刺激，需要进行空间视觉检测，而O. pumila则不需要。但是，O。wendtii' 当骨架内的色谱收缩时，s的响应消失。结合免疫组织化学，组织学和同步加速器显微照相技术，我们在原位重建了光感受器模型，并提取了O. wendtii和O. pumila的估计角孔径。从这些模型得出的角度灵敏度估计值支持以下假设：色谱构成了温氏梭菌的筛选机制，提供了足够的分辨力来检测刺激。RNA测序（RNA-seq）鉴定了这两个物种中的视蛋白候选物，包括多种r-视蛋白和转导途径成分，与免疫组织化学和其他棘皮动物的研究一致[10，11]。最后，我们注意到实验过程中两个物种之间不同的身体姿势可能反映了信号整合的方面。