Abstract
Retinas of 11 species of elasmobranchs from 6 families including deep sea forms were examined by light microscopy. Variations in retinal structure were correlated with depth of capture. The retinas of shallow water forms had a well developed pigment epithelium, cone photoreceptors, numerous short rod outer segments and large horizontal cells with two or three layers. The retinas of deep sea species are characterized by possessing a reduced pigment epithelium, cone-free retinas and their rods have comparatively longer outer segments. No clear identification of bipolar, horizontal and amacrine cells was possible, but there are certainly no highly differentiated horizontal cells of the kind found in most shallow water fish retinas. However, the retinal structures of elasmobranchs are rather standardized and the dramatic variations of retinal structures which often occur in teleosts were not found in this observation.
