Retina of Bouton's skink (reptilia, scincidae): Visual cells, fovea, and ecological constraints
Article first published online: 29 JUN 2001
Copyright © 2001 Wiley-Liss, Inc.
Journal of Comparative Neurology
Volume 436, Issue 4, pages 487–496, 6 August 2001
How to Cite
Röll, B. (2001), Retina of Bouton's skink (reptilia, scincidae): Visual cells, fovea, and ecological constraints. J. Comp. Neurol., 436: 487–496. doi: 10.1002/cne.1082
- Issue published online: 29 JUN 2001
- Article first published online: 29 JUN 2001
- Manuscript Accepted: 15 MAY 2001
- Manuscript Revised: 26 JAN 2001
- Manuscript Received: 6 JUL 2000
- pure-cone retina;
- oil droplets;
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. J. Comp. Neurol. 436:487–496, 2001. © 2001 Wiley-Liss, Inc.