Observations on the Retinal Structure of a Freshwater Carp Cyprinion macrostomus (Heckel) PDF

Keywords

retina, carp, biology

Abstract

The structure of the retina of the light adapted fish Cyprinion macrostomus has been studied by light microscopy, and this revealed that the basic plan of retinal structure resembles that of other freshwater fishes, except for certain specific differences and specialization which are also noted in this study. The pigmented epithelium is composed of a single layer of cuboidal cells with long processes filled with extensive melanin pigments. The contact of the epithelial cell processes with the outer segments of the visual cell are also noted and correlated with the retinomotor reponses. The slender rod cells are distributed singly or in clusters among the cone cells. the latter are of five types: short and long singles, equal and unequal doubles and occasional triple cones. These cones are often arranged in a well defined square mosaic pattern in tangential sections. This pattern may reveal the degree of retinal development. The lipid-like droplets have been observed in the scleral part of the cone ellipsoid. The present finding has been discussed in the light of existing knowledge about the occurrence of different cone types and oil droplets in the retina of different freshwater fishes.