Malmström Tim, Kröger Ronald H H
Department of Cell and Organism Biology, Lund University, Zoology Building, Helgonavägen 3, 22362 Lund, Sweden.
J Exp Biol. 2006 Jan;209(Pt 1):18-25. doi: 10.1242/jeb.01959.
Animal eyes that are primarily used under low-light conditions usually have optical systems of short depth of focus, such that chromatic defocus may lead to considerable blurring of the images. In some vertebrates, the problem is solved by multifocal lenses having concentric zones of different focal lengths, each of which focuses a different relevant spectral range onto the retina. A partially constricted circular pupil would shade the peripheral zones of the lens, leading to the loss of well-focused images at relevant wavelengths. The slit pupil, however, allows for use of the full diameter of the lens even in bright light. We studied species of terrestrial vertebrates from a variety of phylogenetic groups to establish how widespread multifocal lenses are and how pupil shapes are adapted to the optical systems. We found that multifocal lenses are common from amphibians to mammals, including primates. Slit pupils were only present in animals having multifocal optical systems. Among the felids, small species have multifocal lenses and slit pupils, while large species have monofocal lenses and round pupils. The Eurasian lynx, a cat of intermediate size, has an intermediate eye design. The functional significance of the absence of multifocal optical systems in large felids remains mysterious, because such systems are present in other large-eyed terrestrial vertebrates. Multifocal optical systems in nocturnal prosimians suggest that those animals have colour vision despite being described as cone monochromats.
主要在低光照条件下使用的动物眼睛通常具有短焦深的光学系统，因此色差散焦可能会导致图像出现相当程度的模糊。在一些脊椎动物中，这个问题通过具有不同焦距同心区域的多焦点透镜得以解决，每个区域将不同的相关光谱范围聚焦到视网膜上。部分收缩的圆形瞳孔会遮挡透镜的周边区域，导致在相关波长下失去聚焦良好的图像。然而，狭缝瞳孔即使在强光下也能使用透镜的整个直径。我们研究了来自各种系统发育类群的陆生脊椎动物物种，以确定多焦点透镜的广泛程度以及瞳孔形状如何适应光学系统。我们发现，从两栖动物到哺乳动物，包括灵长类动物，多焦点透镜都很常见。狭缝瞳孔仅出现在具有多焦点光学系统的动物中。在猫科动物中，小型物种有多焦点透镜和狭缝瞳孔，而大型物种有单焦点透镜和圆形瞳孔。中等体型的欧亚猞猁具有中等的眼睛设计。大型猫科动物中缺乏多焦点光学系统的功能意义仍然是个谜，因为这种系统在其他大眼睛的陆生脊椎动物中存在。夜行性原猴类的多焦点光学系统表明，尽管这些动物被描述为视锥单色素动物，但它们具有色觉。
