Centre for Behavioural Biology, School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK.
J Exp Biol. 2013 Dec 1;216(Pt 23):4454-61. doi: 10.1242/jeb.094136.
Intraspecific differences in retinal physiology have been demonstrated in several vertebrate taxa and are often subject to adaptive evolution. Nonetheless, such differences are currently unknown in birds, despite variations in habitat, behaviour and visual stimuli that might influence spectral sensitivity. The parrot Platycercus elegans is a species complex with extreme plumage colour differences between (and sometimes within) subspecies, making it an ideal candidate for intraspecific differences in spectral sensitivity. Here, the visual pigments of P. elegans were fully characterised through molecular sequencing of five visual opsin genes and measurement of their absorbance spectra using microspectrophotometry. Three of the genes, LWS, SW1 and SWS2, encode for proteins similar to those found in other birds; however, both the RH1 and RH2 pigments had polypeptides with carboxyl termini of different lengths and unusual properties that are unknown previously for any vertebrate visual pigment. Specifically, multiple RH2 transcripts and protein variants (short, medium and long) were identified for the first time that are generated by alternative splicing of downstream coding and non-coding exons. Our work provides the first complete characterisation of the visual pigments of a parrot, perhaps the most colourful order of birds, and moreover suggests more variability in avian eyes than hitherto considered.
已经在几个脊椎动物分类群中证明了视网膜生理学的种内差异，并且这些差异通常受到适应性进化的影响。尽管如此，鸟类的这种差异目前尚不清楚，尽管栖息地、行为和视觉刺激等因素可能会影响光谱灵敏度。金刚鹦鹉 Platycercus elegans 是一个物种复合体，亚种之间（有时甚至在亚种内）的羽毛颜色差异极大，使其成为研究光谱灵敏度种内差异的理想候选物种。在这里，通过对五个视蛋白基因进行分子测序，并使用微分光光度法测量其吸收光谱，全面表征了 P. elegans 的视觉色素。其中三个基因，LWS、SW1 和 SWS2，编码的蛋白质与其他鸟类中的蛋白质相似；然而，RH1 和 RH2 色素的多肽羧基末端长度和性质都不同，这是以前任何脊椎动物视觉色素都没有的特性。具体来说，首次鉴定出多种 RH2 转录本和蛋白变体（短、中、长），它们是通过下游编码和非编码外显子的选择性剪接产生的。我们的工作首次对鹦鹉的视觉色素进行了全面描述，这可能是鸟类中颜色最鲜艳的一个目，而且还表明鸟类眼睛的变异性比以前认为的更大。
