Histopathological analysis of Nile tilapia organs grown in aquaculture conditions in southern Russia

Today, aquaculture is one of the largest and fastest growing areas in agriculture. Breeding and rearing of aquatic organisms is accompanied by constant monitoring of morphophysiological indicators of their health and painstaking creation of favorable conditions for increasing productivity and eliminating pathological conditions of aquaculture facilities. Morphohistological methods are one of the frequently used tools for an objective assessment of the condition of cultivated aquatic organisms. The results of a histopathological analysis of the gills, liver, and throat of the Nile tilapia (Oreochromis niloticus) grown in pond farming are presented, followed by a ranking of histopathological changes. The gills, liver, and spleen were examined. Changes of varying degrees (from minor to pronounced) were detected in the gills. The most common disorders were changes in the shape of lamellae and hyperplasia of the interlamellar epithelium of the filament. Disorders of blood rheology manifested themselves in the form of vasodilation of the filament, stasis, and thrombosis. Mononuclear inflammatory infiltrates, capillary thrombosis at the bases of lamellae, and epithelial cysts were also observed. The most frequently observed liver reaction was a violation of the rheology of blood, mainly capillaries. Such types of pathology as lipid dystrophy and vacuolar dystrophy were noted. There were also signs of necrosis in the form of karyopycnosis, focal necrosis. Along with dystrophies and necrosis, foci of melanomacrophages and vacuolar degeneration of pancreatic acinuses were detected in the parenchyma of such organs. The spleen tissue was characterized by a slight degree of changes, but there was a violation of blood rheology in the form of stasis in vessels of different calibers, and hemosiderin deposition and the presence of inflammatory eosinophilic granular infiltrates were noted.