Arrese Catherine A, Hart Nathan S, Thomas Nicole, Beazley Lyn D, Shand Julia
Department of Zoology-WAIMR, University of Western Australia, WA 6009, Crawley, Australia.
Curr Biol. 2002 Apr 16;12(8):657-60. doi: 10.1016/s0960-9822(02)00772-8.
Vertebrate color vision is best developed in fish, reptiles, and birds with four distinct cone receptor visual pigments. These pigments, providing sensitivity from ultraviolet to infrared light, are thought to have been present in ancestral vertebrates. When placental mammals adopted nocturnality, they lost two visual pigments, reducing them to dichromacy; primates subsequently reevolved trichromacy. Studies of mammalian color vision have largely overlooked marsupials despite the wide variety of species and ecological niches and, most importantly, their retention of reptilian retinal features such as oil droplets and double cones. Using microspectrophotometry (MSP), we have investigated the spectral sensitivity of the photoreceptors of two Australian marsupials, the crepuscular, nectivorous honey possum (Tarsipes rostratus) and the arhythmic, insectivorous fat-tailed dunnart (Sminthopsis crassicaudata); these species are representatives of the two major taxonomic divisions of marsupials, the diprotodonts and polyprotodonts, respectively. Here, we report the presence of three spectrally distinct cone photoreceptor types in both species. It is the first evidence for the basis of trichromatic color vision in mammals other than primates. We suggest that Australian marsupials have retained an ancestral visual pigment that has been lost from placental mammals.
脊椎动物的色觉在鱼类、爬行动物和鸟类中最为发达，它们拥有四种不同的视锥细胞受体视觉色素。这些色素能提供从紫外线到红外线的感光度，被认为在脊椎动物祖先中就已存在。当胎盘哺乳动物适应夜行性时，它们失去了两种视觉色素，变为双色视觉；灵长类动物随后又重新进化出了三色视觉。尽管有各种各样的物种和生态位，而且最重要的是，有袋类动物保留了诸如油滴和双锥细胞等爬行动物视网膜特征，但对哺乳动物色觉的研究在很大程度上忽略了有袋类动物。我们使用显微分光光度法（MSP）研究了两种澳大利亚有袋类动物的光感受器的光谱敏感度，这两种动物分别是黄昏活动、以花蜜为食的蜜袋鼯（Tarsipes rostratus）和无节律、以昆虫为食的肥尾袋鼬（Sminthopsis crassicaudata）；这两个物种分别代表了有袋类动物的两个主要分类科，即双门齿目和多门齿目。在此，我们报告这两个物种中都存在三种光谱不同的视锥光感受器类型。这是灵长类以外的哺乳动物三色视觉基础的首个证据。我们认为澳大利亚有袋类动物保留了一种胎盘哺乳动物已失去的祖传视觉色素。
