Foster R G, Helfrich-Förster C
Department of Integrative and Molecular Neuroscience, Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK.
Philos Trans R Soc Lond B Biol Sci. 2001 Nov 29;356(1415):1779-89. doi: 10.1098/rstb.2001.0962.
A circadian clock has no survival value unless biological time is adjusted (entrained) to local time and, for most organisms, the profound changes in the light environment provide the local time signal (zeitgeber). Over 24 h, the amount of light, its spectral composition and its direction change in a systematic way. In theory, all of these features could be used for entrainment, but each would be subject to considerable variation or 'noise'. Despite this high degree of environmental noise, entrained organisms show remarkable precision in their daily activities. Thus, the photosensory task of entrainment is likely to be very complex, but fundamentally similar for all organisms. To test this hypothesis we compare the photoreceptors that mediate entrainment in both flies and mice, and assess their degree of convergence. Although superficially different, both organisms use specialized (employing novel photopigments) and complex (using multiple photopigments) photoreceptor mechanisms. We conclude that this multiplicity of photic inputs, in highly divergent organisms, must relate to the complex sensory task of using light as a zeitgeber.
昼夜节律时钟没有生存价值，除非生物时间被调整（校准）到当地时间，而且对大多数生物来说，光照环境的深刻变化提供了当地时间信号（授时因子）。在24小时内，光的量、光谱组成及其方向会以系统的方式变化。理论上，所有这些特征都可用于校准，但每个特征都会受到相当大的变化或“噪声”影响。尽管存在高度的环境噪声，但校准后的生物在其日常活动中表现出显著的精确性。因此，校准的光感任务可能非常复杂，但对所有生物来说基本相似。为了验证这一假设，我们比较了介导果蝇和小鼠校准的光感受器，并评估它们的趋同程度。尽管表面上不同，但这两种生物都使用专门的（采用新型光色素）和复杂的（使用多种光色素）光感受器机制。我们得出结论，在高度不同的生物中，这种多种光输入必然与将光用作授时因子的复杂感觉任务有关。
