A histological study of the black-winged kite's retina (Elanus caeruleus, Desfontaines, 1789)

Abstract

The study showed the retina of the diurnal invasive raptor Elanus caeruleus is avascular and supplied nutrition and oxygen by the choroid and pecten oculi. The retina includes two layers: the outer layer is called the pigmented epithelium, and the inner layer is the neural layer. The neural layer consists of nine layers: visual cells layer, outer limiting membrane, external nuclear layer, external plexiform layer, internal nuclear layer, internal plexiform layer, ganglion cell layer, nerve fiber layer and inner limiting membrane. The visual cell layer consists of double cones, single cones and rods, and the cones are more than the rods. The external nuclear layer appears to have compact visual cells. The inner nuclear layer is characterized by its diverse and highly compact cells, which consist of bipolar cells, horizontal cells, amacrine cells, and Muller cells. The internal plexiform layer is thicker than the external plexiform layer. The retina contains the deep and shallow fovea. The deep fovea is distinguished by convex walls around the deep and wide pit. The pit of the deep fovea has only thin cones, reduced numbers of cells in the inner nuclear layer, and a lack of ganglion cells. The shallow fovea contains all the retinal layers present at the pit. However, the rows of the inner retinal layer are fewer in number than in the area adjacent to the parafovea.

Received 09/09/2023

Revised 14/11/2023

Accepted 16/11/2023

Published Online First 20/06/2024