The salamander clade Eurycea from the karst regions of central Texas provides an ideal platform for comparing divergent nervous and sensory systems since some species exhibit extreme phenotypes thought to be associated with inhabiting a subterranean environment, including highly reduced eyes, while others retain an ancestral ocular phenotype appropriate for life above ground. We describe ocular morphology, comparing three salamander species representing two phenotypes—the surface-dwelling Barton Springs salamander (E. sosorum) and San Marcos salamander (E. nana) and the obligate subterranean Texas blind salamander (E. rathbuni) - in terms of structure and size of their eyes. Eyes were examined using confocal microscopy and measurements were made using ImageJ. Statistical analysis of data was carried out using R. We also provide a developmental series and track eye development and immunolocalization of Pax6 in E. sosorum and E. rathbuni. Adult histology of the surface-dwelling San Marcos salamander (E. nana) shows similarities to E. sosorum. The eyes of adults of the epigean species E. nana and E. sosorum appear fully developed with all the histological features of a fully functional eye. In contrast, the eyes of E. rathbuni adults have fewer layers, lack lenses and other features associated with vision as has been reported previously. However, in early developmental stages eye morphology did not differ significantly between E. rathbuni and E. sosorum. Parallel development is observed between the two phenotypes in terms of morphology; however, Pax6 labeling seems to decrease in the latter stages of development in E.rathbuni. We test for immunolabeling of the visual pigment proteins opsin and rhodopsin and observe immunolocalization around photoreceptor disks in E. nana and E. sosorum, but not in the subterranean E. rathbuni. Our results from examining developing salamanders suggest a combination of underdevelopment and degeneration contribute to the reduced eyes of adult E. rathbuni.

中文翻译：

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得克萨斯州中部的上层蝾螈和地下蝾螈（Eurycea）的比较发育和眼部组织学

来自德克萨斯州中部喀斯特地区的蝾螈进化枝 Eurycea 为比较不同的神经和感觉系统提供了一个理想的平台，因为一些物种表现出被认为与居住在地下环境有关的极端表型，包括高度缩小的眼睛，而其他物种保留了祖先的眼表型适合地上生活。我们描述了眼部形态，比较了代表两种表型的三种蝾螈物种——生活在地表的巴顿斯普林斯蝾螈（E. sosorum）和圣马科斯蝾螈（E. nana）以及专性地下的德克萨斯盲蝾螈（E.rathbuni）——他们眼睛的结构和大小。使用共聚焦显微镜检查眼睛并使用 ImageJ 进行测量。使用R进行数据的统计分析。我们还提供发育系列并跟踪 E. sosorum 和 E.rathbuni 中 Pax6 的眼睛发育和免疫定位。生活在地表的圣马科斯蝾螈（E. nana）的成体组织学显示出与 E. sosorum 的相似之处。后生物种 E. nana 和 E. sosorum 的成虫的眼睛看起来完全发育，具有功能齐全的眼睛的所有组织学特征。相比之下，E.rathbuni 成年人的眼睛层数较少，缺乏晶状体和其他与先前报道的视觉相关的特征。然而，在早期发育阶段，E.rathbuni 和 E.sosorum 之间的眼睛形态没有显着差异。两种表型在形态学上是平行发展的；然而，在 E.rathbuni 发育的后期阶段，Pax6 标记似乎减少了。我们测试了视觉色素蛋白视蛋白和视紫质的免疫标记，并观察了 E. nana 和 E. sosorum 中光感受器盘周围的免疫定位，但不在地下 E.rathbuni 中。我们检查发育中的蝾螈的结果表明，发育不全和退化的结合导致成年 E.rathbuni 的眼睛减少。