Röll B
Lehrstuhl für Tierphysiologie, Fakultät für Biologie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
J Comp Neurol. 2001 Aug 6;436(4):487-96. doi: 10.1002/cne.1082.
Bouton's skink, Cryptoblepharus boutonii africanus, is a small, diurnal lizard living on outcrops along the coast of East Africa under high ambient light intensities. It is characterized by relatively large eyes (maximal diameter about 2 mm), with immovable eyelids forming a transparent spectacle and with a virtually constant pupil diameter. The single fovea in the central retina is well developed, with a clearly defined pit, which is relatively deep but not funnel-shaped. The foveal pit is not devoid of the outer nuclear and outer plexiform layers; only the main part of the inner nuclear layer is displaced laterally, resulting in a pit with gradual sloping towards its edges. Thus, the fovea appears to be concaviclivate, as in the eyes of lacertids, varanids, and gekkonids. The central position of the foveae in these laterally placed scincid eyes corresponds with monocular fixation, e.g., of detected prey. C. boutonii has a pure-cone retina containing single and double visual cells. The latter consist of two cells of unequal sizes. Yellowish oil droplets are present in single cones and the minor members of the double cones in all retinal regions. The visual cells of the different retinal regions do not differ in the ultrastructure of their components but differ considerably in size. The outer segments of the foveal cones are twice as long as those of the peripheral cones. Except for the pedicles, the diameters of the components of the visual cells decrease towards the fovea, resulting in an increase in visual acuity.
布顿氏石龙子（Cryptoblepharus boutonii africanus）是一种小型昼行性蜥蜴，生活在东非海岸的露头区域，环境光照强度较高。它的特点是眼睛相对较大（最大直径约2毫米），眼睑不能活动，形成透明的眼膜，瞳孔直径几乎恒定。中央视网膜上的单个中央凹发育良好，有一个清晰界定的凹陷，相对较深但不是漏斗状。中央凹的凹陷处并非没有外核层和外网状层；只是内核层的主要部分向侧面移位，导致凹陷向边缘逐渐倾斜。因此，中央凹看起来是凹面状的，就像蜥蜴科、巨蜥科和壁虎科动物的眼睛一样。在这些位于侧面的石龙子眼睛中，中央凹的中心位置与单眼注视相对应，例如注视被发现的猎物。布顿氏石龙子有一个纯视锥细胞视网膜，包含单视细胞和双视细胞。双视细胞由两个大小不等的细胞组成。在所有视网膜区域的单视锥细胞和双视锥细胞的较小成员中都存在淡黄色油滴。不同视网膜区域的视细胞在其组成部分的超微结构上没有差异，但在大小上有很大差异。中央凹视锥细胞的外段是周边视锥细胞外段的两倍长。除了视锥细胞的蒂部，视细胞组成部分的直径向中央凹方向减小，导致视力增加。
