A Comparative Histological Study of the Retina in the Two Types of Iraqi Vertebrates

The study has aimed to recognize the histological structure of retina in the eye of two Iraqi vertebrates, the difference of the class, the environment and the nature of nutrition, Iraqi spiny-tailed lizard Saara loricata, and white-breasted kingfisher Halcyon smyrnensis. The results show that the retina is a vascular in both species, that consists of two main layers pigmented epithelium and neural layer, which compose of nine layers are visual cell layer, outer limiting membrane, external nuclear layer, external plexiform layer, internal nuclear layer, internal plexiform layer, ganglion cell layer, optic nerve fiber layer and inner limiting membrane. The pigmented epithelium consists of cuboidal epithelial cells, extending cytoplasmic projection toward visual cells. The visual cell layer in Iraqi spiny-tailed lizard was composed of cones only, while in white-breasted kingfisher was composed of rods and cones. The external plexiform layer is less thicker than the internal plexiform layer in both type. The numbers of rows external nuclear layer are less than the number of rows the internal nuclear layer in the studied species. It can be concluded that the differences in the density of visual cells in the species studied are due to increase visual acuity and light level sensitivity.