Gross histological review of the scleral cartilage found in catfish (Silurus triostegus)

Abstract

Background and Objectives: Silurus triostegus is a native catfish of the Iraqi Tigris and Euphrates river basin. It has both ecological and economic importance. Although some studies have focused on its ecology and behavior, no extensive studies have shed light on its histology, especially the eye histology of Silurus triostegus. Scleral cartilage is such an element, found in the outer skeleton of many non-mammalian vertebrates. It provides structure and may serve another adaptive function in aquatic species. The aim of this study was to investigate the morphology and histology of the scleral cartilage in bottom-dwelling teleosts.

Methods: 20 histological eye samples were collected and processed using standard paraffin embedding and hematoxylin and eosin staining techniques.

Results: Histological examination showed a distinct layer of hyaline cartilage posterior to the choroid. The cartilage showed typical features, including lacunae containing single chondrocytes, a homogeneous ground substance, and collagen fiber bundles that continue into the sclera. The photoreceptor layer, pigmented choroid, and choroidal capillary were also well defined, representing a well-structured retina.

Conclusion: These findings confirm the presence of scleral cartilage that provides support and rigidity to the ocular structure of Silurus triostegus, suggesting great adaptability in response to the surrounding environment.