Lizards are excellent models to study the adaptations of the visual system to different scenarios, and surface-dwelling representatives have been relatively well studied. In contrast, very little is known about the functional anatomy of the eyes of fossorial lineages, and properties such as the light transmission by the ocular media have never been characterised in any fossorial species. Some lizards in the family Gymnophthalmidae endemic to the sand dunes of North Eastern Brazil have evolved sand-burrowing habits and nocturnal activity. Lizards in the sister group to Gymnophthalmidae, the family Teiidae, have decidedly diurnal and epigeal lifestyles, yet they are equally poorly known in terms of visual systems. We focussed on the eye anatomy, photoreceptor morphology and light transmittance properties of the ocular media and oil droplets in the gymnophthalmid Calyptommatus nicterus and the teiid Ameivula ocellifera. The general organisation of the eyes of the fossorial nocturnal C. nicterus and the epigeal diurnal A. ocellifera is remarkably similar. The lenses are highly transmissive to light well into the ultraviolet part of the spectrum. The photoreceptors have the typical cone morphology, with narrow short outer segments and oil droplets. The main difference between the two species is that C. nicterus has only colourless oil droplets, whereas A. ocellifera has colourless as well as green-yellow and pale-orange droplets. Our results challenge the assumption that fossorial lizards undergo loss of visual function, a claim that is usually guided by the reduced size and external morphology of their eyes. In the case of C. nicterus, the visual system is well suited for vision in bright light and shows specialisations that improve sensitivity in dim light, suggesting that they might perform some visually-guided behaviour above the surface at the beginning or the end of their daily activity period, when light levels are relatively high in their open dunes habitat. This work highlights how studies on the functional anatomy of sensory systems can provide insights into the habits of secretive species.

中文翻译：

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有视野的沙丘：新热带化石蜥蜴的眼睛

蜥蜴是研究视觉系统对不同场景的适应的优秀模型，而地表栖息的代表已经得到了相对较好的研究。相比之下，对于颅骨谱系的眼睛的功能解剖学知之甚少，并且从未在任何颅骨物种中表征过眼介质的光传输等特性。巴西东北部沙丘特有的裸眼科蜥蜴科的一些蜥蜴已经进化出挖沙习性和夜间活动。Gymnophthalmidae 的姐妹群（Teiidae）中的蜥蜴具有明显的昼夜和表皮生活方式，但它们在视觉系统方面同样鲜为人知。我们专注于眼睛解剖，裸眼科 Calyptommatus nicterus 和 teiid Ameivula ocellifera 眼介质和油滴的光感受器形态和透光率特性。fossorial 夜间 C. nicterus 和 epigeal 日间 A. ocellifera 的眼睛的一般组织非常相似。这些透镜对进入光谱的紫外部分的光具有高度透射性。感光器具有典型的锥形形态，具有狭窄的短外段和油滴。这两个物种之间的主要区别在于，C. nicterus 只有无色油滴，而 A. ocellifera 有无色以及绿黄色和淡橙色的油滴。我们的结果挑战了化石蜥蜴失去视觉功能的假设，通常以缩小的眼睛大小和外部形态为指导的主张。就黄褐斑蝽而言，视觉系统非常适合在强光下进行视觉，并显示出提高在昏暗光线下敏感度的特化能力，这表明它们可能在开始或结束时在表面上方执行一些视觉引导行为日常活动期，此时其开放沙丘栖息地的光照水平相对较高。这项工作强调了对感觉系统功能解剖学的研究如何提供对秘密物种习性的洞察。这表明它们可能会在日常活动开始或结束时在地表上方进行一些视觉引导的行为，此时它们的开放沙丘栖息地的光照水平相对较高。这项工作强调了对感觉系统功能解剖学的研究如何提供对秘密物种习性的洞察。这表明它们可能会在日常活动开始或结束时在地表上方进行一些视觉引导的行为，此时它们的开放沙丘栖息地的光照水平相对较高。这项工作强调了对感觉系统功能解剖学的研究如何提供对秘密物种习性的洞察。