Molecular palaeontology illuminates the evolution of ecdysozoan vision

Colour vision is known to have arisen only twice – once in Vertebrata and once within the Ecdysozoa, in Arthropoda. However, the evolutionary history of ecdysozoan vision is unclear. At the molecular level, visual pigments, composed of a chromophore and a protein belonging to the opsin family, have different spectral sensitivities and these mediate colour vision. At the morphological level, ecdysozoan vision is conveyed by eyes of variable levels of complexity; from the simple ocelli observed in the velvet worms (phylum Onychophora) to the marvellously complex eyes of insects, spiders and crustaceans. Here we explore the evolution of ecdysozoan vision at both the molecular and morphological level; combining analysis of a large-scale opsin dataset that includes previously-unknown ecdysozoan opsins with morphological analyses of key Cambrian fossils with preserved eye structures. We found that while several non-arthropod ecdysozoan lineages have multiple opsins, arthropod multi-opsin visi...已知彩色视觉仅独立演化出现过两次：一次发生在脊椎动物（Vertebrata）中，另一次则发生在蜕皮动物（Ecdysozoa）的节肢动物门（Arthropoda）内。然而，蜕皮动物视觉系统的演化历程仍不明确。在分子层面，视觉色素由生色团（chromophore）和视蛋白（opsin）家族的蛋白质组成，其具有不同的光谱敏感性，介导了彩色视觉的产生。在形态层面，蜕皮动物的视觉系统由复杂度各异的眼部结构承载：从天鹅绒蠕虫（有爪动物门Onychophora）的简单单眼（ocelli），到昆虫、蜘蛛与甲壳类动物精妙复杂的眼部结构。本研究从分子与形态两个层面探究蜕皮动物视觉系统的演化：我们整合了对包含此前未被发现的蜕皮动物视蛋白的大规模视蛋白数据集的分析，以及对保存有眼部结构的关键寒武纪（Cambrian）化石的形态学分析。我们的研究结果显示，尽管多个非节肢动物的蜕皮动物支系拥有多种视蛋白，但节肢动物的多视蛋白视觉……