Histological Structure of the Gills and Respiratory Surface Area of the Trachurus Mediterraneus Caught from the Coast of Misurata City

The gills function to supply the body with the oxygen necessary for the physiological processes occurring in fish. Their efficiency varies depending on the species, and the gills' surface area is one factor that determines the fish's efficiency and activity level. A rotary microtome was used to prepare tissue sections of the gills of Trachurus mediterraneus, a species found along the coast of Misurata city, to study the histological structure and estimate the respiratory surface area during May 2024. The macroscopic examination revealed the shape of the gill arches, with an average of 131.75±0.5 gill filaments arranged in an orderly manner on the dorsal surface of the gill arch, with an average length of 38.75 ± 1.25 µm. The average number of primary lamellae was 229.5±57.44, with an average length of 2.21±0.43 µm. Histologically, the gill lamellae are covered by two layers of epithelial cells, while the secondary lamellae are covered by a single layer of epithelial cells, along with supporting cells within their structure. The gill filaments are supported by cartilage tissue, and there are several blood sinuses and lacunae. The absolute and relative respiratory surface areas of the gills of T. mediterraneus were 148.5888 m² and 0.425319, respectively. The histological structure indicates that the studied fish possess cartilage supporting the gill filaments and numerous blood sinuses. The primary lamellae are lined with stratified epithelial cells, while the secondary lamellae are lined with simple epithelial cells. Additionally, pillar cells are present, supporting the secondary lamellae and enclosing many blood spaces. The histological structure and micrometric measurements play a crucial role in understanding the physiological activity of fish, which is oxygen-dependent, and the structural and histological adaptations of the gill filaments.