The Role of the Ocular Lids of the Black-Winged Kite, Elanus caeruleus, in the Immune Protection of the EyeNahed Ahmed Shawki1, Abdelraheim H Attaai2, Amany Mohamed Abdel- Mageed1, Fatma Abdel- Regal Mahmoud11 Assiut University, Faculty of Science. Zoology Department, Assiut, Egypt.2 Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Assiut University, Assiut, Assiut 71526, Egypt.2 Department of Anatomy and Histology, School of Veterinary Medicine, Badr University in Assiut, Assiut 11829, Egypt; abdelraheim.attaai@aun.edu.eg

The aim of the study was to describe the morphological features and microstructure of the upper, lower, and third eyelids of black-winged kite, Elanus caeruleus, as well as characterize the organized lymphoid follicles and lymphocytes in the eyelid’s mucosa, and to illustrate the importance of the eye adnexa in the eye’s immune protection. The black-winged kite has large forward-facing eyes placed under a bony shelf (lacrimal process) that shaded them. Both eyelids have thick and pigmented edges and bear two rows of long and finely modified filoplume feathers that increase at the anterior canthus. It was found that the lower eyelid appears longer and thinner than the upper one, as well as having sparse feathers on the skin surface of the lower eyelid but lack on the upper. The third eyelid is a white opaque membrane moving obliquely over the cornea surface. The melanocytes appear in the stratum basal of upper and lower eyelids and the Langerhans cells were observed within the layers of stratum spinosum, near the feather follicle and around the blood vessel. Aggregations of lymphatic cells were present under the conjunctival epithelium within the stroma of the lower eyelid (in the orbital zone near the tarsal plate), while absent in the upper eyelid and nictitating membrane. The present study revealed that many high endothelial venues (HEV) are distributed along the lower eyelid and increase in the palpebral marginalis, while in the upper eyelid, it is restricted in the marginal region. The density of goblet cells on the conjunctiva surface of the upper eyelid and the nictitating membrane is higher than that of the lower eyelid. The leading edge and bulbi surface of the third eyelid reveal the irregular surface of the apical cell, with many cilia having variable amounts of secretory vesicles as shown by TEM.