Animals have evolved light-sensitive G protein–coupled receptors, known as opsins, to detect coherent and ambient light for visual and nonvisual functions. These opsins have evolved to satisfy the particular lighting niches of the organisms that express them. While many unique patterns of evolution have been identified in mammals for rod and cone opsins, far less is known about the atypical mammalian opsins. Using genomic data from over 400 mammalian species from 22 orders, unique patterns of evolution for each mammalian opsins were identified, including photoisomerases, RGR-opsin (RGR) and peropsin (RRH), as well as atypical opsins, encephalopsin (OPN3), melanopsin (OPN4), and neuropsin (OPN5). The results demonstrate that OPN5 and rhodopsin show extreme conservation across all mammalian lineages. The cone opsins, SWS1 and LWS, and the nonvisual opsins, OPN3 and RRH, demonstrate a moderate degree of sequence conservation relative to other opsins, with some instances of lineage-specific gene loss. Finally, the photoisomerase, RGR, and the best-studied atypical opsin, OPN4, have high sequence diversity within mammals. These conservation patterns are maintained in human populations. Importantly, all mammalian opsins retain key amino acid residues important for conjugation to retinal-based chromophores, permitting light sensitivity. These patterns of evolution are discussed along with known functions of each atypical opsin, such as in circadian or metabolic physiology, to provide insight into the observed patterns of evolutionary constraint.

动物进化出了光敏 G 蛋白偶联受体（称为视蛋白），可以检测相干光和环境光，从而实现视觉和非视觉功能。这些视蛋白已经进化以满足表达它们的生物体的特定照明生态位。虽然在哺乳动物中发现了视杆细胞和视锥细胞视蛋白的许多独特的进化模式，但对非典型哺乳动物视蛋白的了解却少之又少。利用 22 个目的 400 多个哺乳动物物种的基因组数据，确定了每种哺乳动物视蛋白的独特进化模式，包括光异构酶、RGR 视蛋白 (RGR) 和视蛋白 (RRH)，以及非典型视蛋白、脑视蛋白 (OPN3)、黑视蛋白(OPN4) 和神经蛋白酶 (OPN5)。结果表明，OPN5 和视紫红质在所有哺乳动物谱系中都表现出极大的保守性。视锥细胞视蛋白 SWS1 和 LWS 以及非视觉视蛋白 OPN3 和 RRH 相对于其他视蛋白表现出中等程度的序列保守性，并且存在一些谱系特异性基因丢失的情况。最后，光异构酶 RGR 和研究最充分的非典型视蛋白 OPN4 在哺乳动物中具有高度的序列多样性。这些保护模式在人群中得以维持。重要的是，所有哺乳动物视蛋白都保留了对于与基于视网膜的发色团结合重要的关键氨基酸残基，从而实现光敏感性。这些进化模式与每个非典型视蛋白的已知功能（例如昼夜节律或代谢生理学）一起讨论，以提供对观察到的进化限制模式的深入了解。