Emond M P, McNeil R, Cabana T, Guerra C G, Lachapelle P
Département de Sciences Biologiques, Université de Montréal, C.P. 6128, Succ. Centre-ville, Montréal, Que., Canada.
Vision Res. 2006 Sep;46(18):2914-25. doi: 10.1016/j.visres.2006.02.023. Epub 2006 May 2.
Ring-billed gulls (Larus delawarensis) and gray gulls (Larus modestus) are two species active both by day and night. We have investigated the retinal adaptations that allow the diurnal and nocturnal behaviours of these two species. Electroretinograms and histological analyses show that both species have a duplex retina in which cones outnumber rods, but the number of rods appears sufficient to provide vision at night. Their retinas respond over the same scotopic dynamic range of 3.4logcdm(-2), which encompasses all of the light levels occurring at night in their photic environment. The amplitudes of the scotopic saturated a- and b-wave responses as well as the photopic saturated b-wave response and the photopic sensitivity parameter S are however higher in ring-billed gulls than in gray gulls. Moreover, the process of dark adaptation is about 30min faster in gray gulls than in ring-billed gulls. Our results suggest that both species have acquired in the course of their evolution functional adaptations that can be related to their specific photic environment.
环嘴鸥（Larus delawarensis）和灰鸥（Larus modestus）是两种昼夜都活跃的物种。我们研究了使这两个物种能够进行昼夜活动的视网膜适应性。视网膜电图和组织学分析表明，这两个物种都具有双重视网膜，其中视锥细胞数量超过视杆细胞，但视杆细胞的数量似乎足以在夜间提供视觉。它们的视网膜在3.4logcdm(-2)的相同暗视动态范围内做出反应，该范围涵盖了它们光环境中夜间出现的所有光照水平。然而，环嘴鸥的暗视饱和a波和b波反应的幅度以及明视饱和b波反应和明视敏感度参数S都比灰鸥高。此外，灰鸥的暗适应过程比环嘴鸥快约30分钟。我们的结果表明，这两个物种在进化过程中都获得了与其特定光环境相关的功能适应性。
