The fine structure of the retinal epithelium in the scissortail (Rasbora trilineata) (Teleost).

The normal morphology of the retinal epithelium has been studied by transmission electron microscopy in the eye of a teleost; the scissortail (Rasbora trilineata). The retinal epithelium forms a single layer of cells joined laterally by cell junctions. Centrally in the retina these cells are columnar while moving peripherally they are cuboidal and eventually squamous in shape. Apical processes of these cells enclose photoreceptor inner and outer segments and reach almost to the external limiting membrane. Few basal infoldings are seen. In addition to the usual cell organelles seen in retinal epithelial cells, i. e., abundant smooth endoplasmic reticulum, numerous mitochondria and phagosomes, the central epithelial cells contain numerous lipid tapetal spheres and a few melanosomes. Peripherally the cells contain few or no tapetal spheres and more melanosomes. A population of wandering phagocytes within the epithelial layer is described. Bruch's membrane shows a three-layered composition rather than the usual pentalaminate structure seen in most vertebrates. The choriocapillaris endothelium facing Bruch's membrane is very thin but displays only a few fenestrae.