Light and Electron Microscopic Characterization of Vascular and Mitochondrial Structures in the Camel Retina

Camels have unique morphological traits that enable them to adapt well to harsh conditions. This work aims to describe the vascular architecture of the camel retina and investigate its cellular components with a focus on the distribution of mitochondria in Muller cells and photoreceptors, using light and electron microscopy. The camel retina is euangiotic in which blood vessels extend in the inner retina from the nerve fiber layer to the outer plexiform layer. The pericytes are embedded in the basement membrane of the retinal capillaries, and overlapping of pericytes could be observed. Glial cells are localized in the vicinity of blood vessels. Muller cells display mitochondria throughout their length, from their end-feet, which form the inner limiting membrane, to their scleral end, which forms the outer limiting membrane. Interestingly, the bodies of camel Muller cells are densely packed with mitochondria, while their end-feet show few mitochondria. Numerous mitochondria could be observed in the axons and synaptic terminals of rods and cones. Photoreceptor bodies are devoid of mitochondria. The inner segment's ellipsoid region is densely packed with mitochondria, whereas the outer segment lacks them. In conclusion, these findings provide new insights into the vascular and cellular organization of the camel retina, highlighting key adaptations such as a well-developed inner retinal vasculature, specialized features of the inner blood-retinal barrier, and a distinctive pattern of mitochondrial distribution in Muller cells and photoreceptors. This structural specialization may play a crucial role in maintaining retinal function under the challenging environmental conditions camels face.