Three-dimensional reconstitution of cone arrangement on the spherical surface of the retina in the Medaka eyes

Abstract

In the retina of the medaka four kinds of retinal cone photoreceptor cells are arranged in a simple, repeating organizational pattern known as a square mosaic. We found that the distribution of cones in the retina could be easily detected by autofluorescence-emission from the photoreceptor cells without any staining. In tangential sections of the retina, cones were located at a specific position in a crystalline lattice as follows: Double cone pairs display a zigzagging appearance, oriented roughly 90-120 degrees to one another, and single cones were in the center of the square consisting of four double cone pairs. In order to determine the continuity of this regular arrangement on the spherical surface, the distribution of this cone mosaic pattern was examined in central, dorsal, ventral, nasal and caudal areas of the retina. The regular arrangement of cones was confirmed in the whole retina. Double cones and single cones are in their respective lines and these lines form a lattice-work. As a result of reconstructing these arrangements on the retinal hemisphere, the lines of this lattice-work of cones were found to be orthogonal to the retinal margin, radiating from the center of the retina-like meridians, and parallel to the retinal margin forming concentric circles that is reminiscent of a longitudinal and a latitudinal lines of a terrestrial globe. This construction of the cone arrangement in whole retina of the medaka was consistent with maintaining a rectangular mosaic in growing retina with newly produced cells only in a marginal cell proliferating zone.