Fine structure of the retinal epithelium in the bushbaby (<i>Galago senegalensis</i>)

Abstract

The fine structure of the retinal epithelial layer has been studied by electron microscopy in the bushbaby (<i>Galago senegalensis</i>). The retinal epithelium over most of the retina is fairly typical of other vertebrates and consists of a single layer of heavily pigmented cuboidal cells joined laterally by cell junctions. These cells display extensive basal (scleral) infoldings and numerous apical (vitreal) processes which enclose photoreceptor outer segments. The bushbaby possesses a choroidal tapetum lucidum located in the posterior fundus. Over this tapetum the retinal epithelial cells are squamous and non-pigmented. However, as in the non-tapetal area, basal infoldings, apical processes and lateral cell junctions are present as are numerous mitochondria and large amounts of smooth endoplasmic reticulum. Rough endoplasmic reticulum is not abundant. Over the tapetal region the typical fenestrated choriocapillaris is displaced and indents the retinal epithelial layer. Bruch’s membrane in such an indented area is reduced to a single basal lamina from its normal pentalaminate structure seen in the non-tapetal area. In the non-tapetal region particularly the tips of the photoreceptor outer segments are composed of an amorphous material rather than typical outer segment discs.