Research Article
Volume 5 Issue 12 - 2021
Comparative Studies on the Histology of Cornea and Iris in Eyes of a Diurnal and a Nocturnal Red Sea Fish
Nora A Aljalaud1* and Ahmad M Azab2
1Biology Department, College of Science, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
2Zoology Department, Faculty of Science, AlAzhar University, Cairo, Egypt
*Corresponding Author: Nora A Aljalaud, Biology Department, College of Science, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia.
Received: December 03, 2021; Published: November 30, 2021


This work aimed to investigate the comparative histological structure of cornea and iris in eyes of nocturnal fish, Priacanthus hamrur and diurnal fish, Siganus rivulatus. Samples of the selected fishes were obtained by hooks from the coral reef habitat at the northern Red Sea coast in Hurghada City, Red Sea Governorate. The collected fish samples were immediately dissected and their eyes were separated from the orbits, cut and immediately fixed in alcoholic Bouin`s fluid for 24 hours. Then, the routine histological procedures were carrid out to eye specimens and finally examined.

The histological results showed that cornea of nocturnal fish, P. hamrur is thicker than the diurnal fish, S. rivulatus. Cornea of P. hamrur consists of corneal epithelium having stratified squamous epithelial type; Bowman’s layer; dermal stroma of loose connective tissue with un-striated smooth muscle fibers and contains some vacuoles in the pupil portion; scleral stroma is very thick, convoluted in the pupil portion and consists of compact collagenous muscle fibers; posteriorly covered by simple squamous epithelium (endothelium) that rests on Descemet's membrane. The Descemet's membrane is not detected in the cornea of S. rivulatus and the collagenous muscle fibers in the scleral stroma are arranged in a precise orthogonal array making a network. Scleral stroma is gradually transformed to the proper sclera containing hyaline cartilage and surrounded by the perichondrium.

 Iris of nocturnal fish, P. hamrur has a thick matted layer of interdigitating melanocytes and fibroblasts. Its stroma is very thick and contains many blood vessels, fibrous connective tissue and richly vascularized. There are smooth muscles of sphincter pupillae and dilator pupillae muscles which extend along most of the iris. Iris of diurnal fish, S. rivulatus has a thin matted layer of melanocytes and fibroblasts. Its stroma is thick and contains many blood vessels, loose connective tissue. There are smooth muscles of sphincter pupillae which extend along most of the iris.

The present study concluded the histological structures of cornea and iris are varied between diurnal and nocturnal fishes to suite the change in the amount of light during day and night.


Keywords: Priacanthus hamrur; Siganus rivulatus; Cornea; Iris; Nocturnal Red Sea Fish


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Citation: Nora A Aljalaud and Ahmad M Azab. “Comparative Studies on the Histology of Cornea and Iris in Eyes of a Diurnal and a Nocturnal Red Sea Fish”. EC Emergency Medicine and Critical Care 5.12 (2021): 144-153.

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