Comparative Histomorphometric and Histochemical Study of the Vertebrates’ Retina

Owing to the great significance of the retina in the visual process of the living individuals, this study came to compare the histological, histomorphometric, and histochemical structures between three vertebrates live in different environmental conditions; namely Carp fish, Dove, and Albino rat. A sample of 30 animals; 10 Carp fishes, 10 Doves, and 10 Albino rats, were used and both eyes were extracted from each animal. 8 paraffin sections from each eye of 7µm thickness were prepared, 1 for Haematoxylin and eosin stain and 7 sections for lectin histochemical study which are UEAI, PNA, SBA, LFA, Con-A, WGA, and SWGA. Image analysis software (Global Lab Image), was used to measure the proportional retinal layer thickness to the total thickness of retina. The histological structure of the retina of the studied vertebrates which was examined under light microscope with haematoxylin and eosin stain was shown to be formed of different morphological details of the retinal layers, like cell number and fiber orientation. The morphometric analysis of the vertebrates’ retinal layers was shown to be variable in the three species studied. In the Carp fish retina the thickest layer was the inner plexiform layer and the thinnest one was the nerve fiber layer. In the Dove retina the thickest layer was the pigment epithelium, while the thinnest one was the nerve fiber layer. The thickest layer in the Albino rat retina was the outer nuclear layer, while the pigment epithelium was the thinnest layer. The lectin histochemistry of the vertebrates’ retinal layers in the three species studied was shown as the following: 1. From the nerve fiber to the photoreceptor layers of the retina: These are marked in all the species by PNA, and also SBA (except in the inner and outer nuclear layers of the Albino rat). WGA marking these layers in Albino rat and Dove (this lectin binds also to the outer nuclear and outer segment of photoreceptor layers in the Carp fish). In the Carp fish, Con-A is a marker of these layers (this lectin binds also to the outer plexiform and photoreceptor layers in the Dove and the Albino rat). The SWGA marking these layers in the Albino rat only (this lectin binds also to the outer plexiform, outer nuclear, and outer segment of photoreceptor layers in the Carp fish and inner and outer plexiform and photoreceptor layers in the Dove). 2. From ganglion cell to the photoreceptor layers of the retina: The UEAI is a retinal marker of these layers in the Dove and Carp fish (except the inner plexiform layer in Carp fish). LFA marks these layers in the Dove (except the inner plexiform layer), but it also binded to the inner nuclear and photoreceptor layers only in the Carp fish and outer nuclear and the outer segment of photoreceptor layers in the Albino rat. 3. The pigment epithelium:
The pigment epithelium was labeled with UEAI, PNA, SBA, Con-A, and LFA in the Dove only.This epithelium was also labeled with WGA and SWGA in the Albino rat retina.