By the grace of Allah, Tikrit University – College of Veterinary Medicine witnessed the defense of the Master’s thesis entitled:
“Histological Insights into the Visual System in Birds: A Comparative Study between Pigeons and Chickens”
submitted by Ms. Ishraq Ahmed Jidou in the field of Veterinary Anatomy and Histology. The defense was held in Dr. Muhannad Maher Hall, in the presence of a number of faculty members and students.
The examination committee consisted of:
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Prof. Dr. Iyad Hamid Ibrahim – تخصص Anatomy / Tikrit University – College of Veterinary Medicine (Chair).
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Assist. Prof. Dr. Siraj Munir Ni’mah – تخصص Veterinary Anatomy and Histology / Al-Qasim Green University – College of Veterinary Medicine (Member).
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Assist. Prof. Dr. Mahmoud Nawfal Mustafa – تخصص Histology and Embryology / Tikrit University – College of Veterinary Medicine (Member).
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Assist. Prof. Dr. Uday Alawi Jassim – تخصص Anatomy and Histology / Tikrit University – College of Veterinary Medicine (Member and Supervisor).
The thesis aimed to conduct a comprehensive comparative histological, immunohistochemical, and morphometric study of the eyeball in chickens (Gallus gallus domesticus) and pigeons (Columba livia domestica). The study was based on 40 samples (20 eyes from each species) to identify structural and functional adaptations associated with the environment and behavior of each species.
Histological examination using Hematoxylin and Eosin staining clearly demonstrated the distinct layers of the eyeball, highlighting the characteristic ten-layered retina in both species, along with detailed identification of the choroid and its vascularization and pigmented epithelium. The dense connective tissue in the corneal stroma was more prominent in chickens, and the scleral supporting cartilage was clearly documented.
Masson’s Trichrome staining further revealed differences in muscular and connective tissue components, showing greater connective tissue density and more pronounced muscular development in the chicken eye, particularly in the sclera and iris. Increased scleral cartilage thickness was also observed in chickens, representing adaptations that enhance protection against mechanical stress and support stable daytime vision.
Morphometric analysis demonstrated that certain retinal layers and photoreceptors were thicker and longer in pigeons, indicating enhanced neural transmission efficiency, improved spatial orientation, and superior visual tracking during flight. These findings support the pigeon’s advantage in low-light vision and motion sensitivity. In contrast, chickens exhibited a significantly higher number of cone cells (p = 0.020), consistent with their adaptation to brightly lit, color-rich daytime environments.
The examination committee commended the scientific effort invested in the thesis and emphasized the significance of its findings in enriching knowledge in veterinary anatomy and histology, given their valuable contribution to understanding avian visual adaptations from a precise structural and functional perspective.
