When reflected from a surface, light can provide a representation of the spatial environment, whilst gross changes in environment light can signal the time of day. The differing sensory demands of using light to detect environmental space and time appear to have provided the selection pressures for the evolution of different photoreceptor systems in the vertebrates, and probably all animals. This point has been well recognised in the non-mammals, which possess multiple opsin/vitamin A-based photoreceptor populations in a variety of sites distributed both within and outside the CNS. By contrast, eye loss in mammals abolishes all responses to light, and as a result, all photoreception was attributed to the rods and cones of the retina. However, studies over the past decade have provided overwhelming evidence that the mammalian eye contains a novel photoreceptor system that does not depend upon the input from the rods and cones. Mice with eyes but lacking rod and cone photoreceptors can still detect light to regulate their circadian rhythms, suppress pineal melatonin, modify locomotor activity, and modulate pupil size. Furthermore, action spectra for some of these responses in rodents and humans have characterised at least one novel opsin/vitamin A-based photopigment, and molecular studies have identified a number of candidate genes for this photopigment. Parallel studies in fish showing that VA opsin photopigment is expressed within sub-sets of inner retina neurones, demonstrates that mammals are not alone in having inner retinal photoreceptors. It therefore seems likely that inner retinal photoreception will be a feature of all vertebrates. Current studies are directed towards an understanding of their mechanisms, determining the extent to which they contribute to physiology and behaviour in general, and establishing how they may interact with other photoreceptors, including the rods and cones. Progress on each of these topics is moving very rapidly. As a result, we hope this review will serve as an introduction to the cascade of papers that will emerge on these topics in the next few years. We also hope to convince the more casual reader that there is much more to vertebrate photoreceptors than the study of retinal rods and cones.

中文翻译：

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脊椎动物中的非杆状，非锥体感光。

当从表面反射时，光可以表示空间环境，而环境光的总体变化可以表示一天中的时间。使用光检测环境空间和时间的不同感官要求似乎为脊椎动物以及可能是所有动物的不同感光系统的进化提供了选择压力。这一点在非哺乳动物中得到了很好的认识，非哺乳动物在中枢神经系统内部和外部分布的多个位置均具有多个视蛋白/维生素A基感光受体群体。相比之下，哺乳动物的视力丧失消除了对光的所有反应，因此，所有光接收都归因于视网膜的视杆和视锥。然而，过去十年的研究提供了压倒性的证据，表明哺乳动物的眼睛包含一种新颖的感光系统，该系统不依赖于视杆和视锥细胞的输入。眼睛有眼但缺乏杆状和锥状光感受器的小鼠仍然可以检测光来调节其昼夜节律，抑制松果体褪黑激素，改变运动能力并调节瞳孔大小。此外，啮齿动物和人类中某些这类反应的作用谱已经表征了至少一种新型视蛋白/维生素A基光致色素，并且分子研究已经确定了该光致色素的许多候选基因。在鱼类中的平行研究表明，VA视蛋白色素在内部视网膜神经元的子集内表达，这表明哺乳动物并不是唯一拥有内部视网膜感光器的动物。因此，视网膜内光接收似乎是所有脊椎动物的特征。当前的研究旨在了解它们的机制，确定它们在总体上对生理和行为的贡献程度，并确定它们如何与其他感光器（包括杆和锥）相互作用。每个主题的进展都非常迅速。因此，我们希望这篇评论能够成为在未来几年中将针对这些主题的一系列论文的介绍。我们还希望说服更休闲的读者，脊椎动物感光器的功能远不止于视网膜视棒和视锥细胞的研究。确定它们在总体上对生理和行为的贡献程度，并确定它们如何与其他感光器（包括棒和视锥）相互作用。每个主题的进展都非常迅速。因此，我们希望这篇评论能够成为在未来几年中将针对这些主题的一系列论文的介绍。我们还希望说服更休闲的读者，脊椎动物感光器的功能远不止于视网膜视棒和视锥细胞的研究。确定它们在总体上对生理和行为的贡献程度，并确定它们如何与其他感光器（包括棒和视锥）相互作用。每个主题的进展都非常迅速。因此，我们希望这篇评论能够成为在未来几年中将针对这些主题的一系列论文的介绍。我们还希望说服更休闲的读者，脊椎动物感光器的功能远不止于视网膜视棒和视锥细胞的研究。我们希望这篇评论可以作为对未来几年将在这些主题上出现的一系列论文的介绍。我们还希望说服更休闲的读者，脊椎动物光感受器比研究视网膜视杆和视锥细胞具有更多的优势。我们希望这篇评论可以作为对未来几年将在这些主题上出现的一系列论文的介绍。我们还希望说服更休闲的读者，脊椎动物感光器的功能远不止于视网膜视棒和视锥细胞的研究。