Knowledge of a species' visual system has far reaching implications that affect our understanding of a species' ecology and evolutionary history. As a model taxon, the heteromyid rodent genus Dipodomys has been valuable in elucidating patterns and mechanisms in biomechanics, ecology, adaptive physiology, biogeography, and more. Although studied extensively, the visual system of Dipodomys has not been described beyond anecdotal mention of their large eyes. Here, the transmittance parameters of the cornea and lens of Ord's kangaroo rat (Dipodomys ordii) were analyzed and photoreceptor proteins (opsins) expressed in the retina were identified with immunohistochemical (IHC) labeling. Retina maps were constructed to illustrate the relative densities of photoreceptor cells expressing short wavelength (SWS1) opsins, middle/long wavelength (MW/LW) opsins, and rhodopsin (RH1). The retina of D. ordii has variable densities of SWS1 opsin with the highest density being ventral to the optic nerve, high density of MW/LW opsin, and uniform distribution and high density of RH1 across the retina. Our results suggest that D. ordii has a UV-sensitive visual system. Composition and densities of MW/LW- and SWS1-expressing cells resemble that of a crepuscular/diurnal species thereby supporting previous authors who have reported such activity patterns. Uniform retinal distribution of RH1 indicates visual acuity at night, also confirming the paradigm of D. ordii as primarily a nocturnal species and suggesting visual acuity at all times of the day in the species. These results demonstrate not only that the species is capable of UV vision and has a retina characteristic of a diurnal mammal, but that many previously unknown photic niche selective advantages likely have shaped the evolution and ecology of this model taxon.

中文翻译：

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奥德袋鼠（Dipodomys ordii）的紫外线视觉

物种视觉系统的知识具有深远的影响，会影响我们对物种生态和进化历史的理解。作为模型分类群，异型啮齿动物属 Dipodomys 在阐明生物力学、生态学、适应性生理学、生物地理学等方面的模式和机制方面具有重要价值。尽管进行了广泛的研究，但除了传闻中提到了它们的大眼睛之外，还没有对 Dipodomys 的视觉系统进行描述。在这里，我们分析了 Ord 袋鼠大鼠 (Dipodomys ordii) 角膜和晶状体的透光率参数，并用免疫组织化学 (IHC) 标记鉴定了在视网膜中表达的光感受器蛋白（视蛋白）。构建视网膜图以说明表达短波长 (SWS1) 视蛋白的感光细胞的相对密度，中/长波长 (MW/LW) 视蛋白和视紫质 (RH1)。D. ordii 的视网膜具有可变密度的 SWS1 视蛋白，密度最高的是视神经的腹侧，高密度的 MW/LW 视蛋白，以及 RH1 在整个视网膜上的均匀分布和高密度。我们的结果表明 D. ordii 具有紫外线敏感的视觉系统。表达 MW/LW 和 SWS1 的细胞的组成和密度类似于黄昏/昼夜物种的组成和密度，从而支持报告此类活动模式的先前作者。RH1 的均匀视网膜分布表明夜间视力，也证实了 D. ordii 作为主要夜间物种的范式，并表明该物种在一天中的所有时间都有视力。