ABSTRACT

This present study was carried out to evaluate the embryonic and post embryonic development of the retina in African catfish and also describes the age-dependent morphological differentiation stages of developing retina. The retinae of larva and also that of adult catfish were studied histologically. The retinae were processed with Haematoxylene and Eosine stain for routine microscopy. Samples were collected from the hatching tank at 12 hour interval till the post larval stages of Fingerlings, Juveniles and Adult stages. Histological characteristics and the distribution pattern of the visual cells, cones and rods in the retina of the eye of African catfish Clarias gariepinus were investigated.  The developmental process of the retinal cells was also examined in the larvae. At all ages, different retinal layers were studied noting the changing shapes of nuclei and measuring the individual layer. A newly-hatched larva had developing lens and undifferentiated retinal cells. The retinal differentiation proceeded rapidly, with the pigment epithelial cells and photoreceptor cells already formed in a 48 hour-old larva. In 84 hour-old larva at the first-feeding stage, the photoreceptor cells consisted of the rods and cones. In larva 140 hour, the rods and cones rapidly increased in number. In retina of 180 hour-old larva, the retinal elements showed inner nuclear cells, inner plexiform layer, outer nuclear cells were layered and retina pigment epithelial layer. The retina of juvenile basically differed from the adult ones. The retina of Adult catfish had all the layers present and fully differentiated. This descriptive laboratory research presents a detailed retinal differentiation pattern, which contributes to the anatomical knowledge of retinal embryology as well as providing a comparative background for pathological deviations.