Department of Psychology, University of California, Santa Barbara, 93106, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2010 May;196(5):379-84. doi: 10.1007/s00359-010-0519-3. Epub 2010 Mar 12.
Only two of the four cone opsin gene families found in vertebrates are represented in contemporary eutherian and marsupial species. Recent genetic studies of two species of South American marsupial detected the presence of representatives from two of the classes of cone opsin genes and the structures of these genes predicted cone pigments with respective peaks in the ultraviolet and long-wavelength portions of the spectrum. The Virginia opossum (Didelphis virginiana), a profoundly nocturnal animal, is the only marsupial species found in North America. The prospects for cone-based vision in this species were examined through recordings of the electroretinogram (ERG), a commonly examined retinal response to photic stimulation. Recorded under flickering-light conditions that elicit signals from cone photoreceptors, the spectral sensitivity of the opossum eye is well accounted for by contributions from the presence of a single cone pigment having peak absorption at 561-562 nm. A series of additional experiments that employed various chromatic adaptation paradigms were conducted in a search for possible contributions from a second (short-wavelength sensitive) cone pigment. We found no evidence that such a mechanism contributes to the ERG in this marsupial.
在现存的真兽类和有袋类物种中，仅发现了脊椎动物中存在的四个视锥光感受蛋白基因家族中的两个。最近对两种南美洲有袋动物的遗传研究检测到了两种视锥光感受蛋白基因的存在，这些基因的结构预测了视锥色素，其各自的峰值分别在光谱的紫外线和长波长部分。弗吉尼亚负鼠（Didelphis virginiana）是一种极度夜行性动物，是仅在北美的有袋类物种。通过记录视网膜电图（ERG），即对光刺激的常见视网膜反应，检查了这种物种基于视锥细胞的视觉的可能性。在闪烁光条件下进行记录，这些条件会引发视锥光感受器的信号，负鼠眼睛的光谱灵敏度很好地解释了存在一个具有 561-562nm 峰值吸收的单一视锥色素的贡献。进行了一系列额外的实验，采用了各种色适应范例，以寻找第二个（短波敏感）视锥色素可能的贡献。我们没有发现这种机制对视锥细胞的 ERG 有贡献的证据。
