Department of Ecology and Evolution, Stony Book University, The State University of New York, Stony Brook, New York, USA.
Department of Life Sciences, Highline College, Des Moines, Washington, USA.
Bioessays. 2022 Oct;44(10):e2200003. doi: 10.1002/bies.202200003. Epub 2022 Aug 26.
The vertebrate retina is said to be inverted because the photoreceptors are oriented in the posterior direction and are thus unable to maximize photodetection under conditions of low illumination. The tapetum lucidum is a photoreflective structure located posterior to the photoreceptors in the eyes of some fish and terrestrial animals. The tapetum reflects light forward, giving incident photons a "second chance" to collide with a photoreceptor, substantially enhancing retinal photosensitivity in dim light. Across vertebrates (and arthropods), there are a wide variety of tapeta that vary in structure, chemical composition, and even tissue architecture, indicating repeated convergent evolution. To date, the tapetum has not been observed in any cephalopod, however, which also possess a camera-like eye, but with the retinal photoreceptors oriented in the anterior direction. We therefore hypothesize that the tapetum lucidum is a compensatory adaptation for the suboptimal design of the inverted retina of vertebrates.
脊椎动物的视网膜被称为倒置，因为光感受器位于后部方向，因此在低光照条件下无法最大限度地进行光电检测。脉络膜在一些鱼类和陆地动物的眼睛中位于光感受器的后部，是一种光反射结构。脉络膜将光向前反射，使入射光子有“第二次机会”与光感受器发生相互作用，从而显著提高在弱光下的视网膜感光度。在整个脊椎动物（和节肢动物）中，有各种各样的脉络膜，它们在结构、化学成分甚至组织结构上都有所不同，这表明它们经历了多次趋同进化。然而，迄今为止，还没有在任何头足类动物中观察到脉络膜，它们也拥有类似相机的眼睛，但视网膜光感受器位于前部方向。因此，我们假设脉络膜是脊椎动物倒置视网膜设计不佳的一种补偿性适应。
