Etiology and histopathological alterations in some body organs of juvenile rainbow trout Oncorhynchus mykiss (Walbaum, 1792) at nitrite poisoning

Abstract

Nitrite is toxic to fishes and is often encountered in recirculation aquaculture systems. The present study was carried out to study gills, liver and kidney histopathology in the juvenile freshwater fish Oncorhynchus mykiss which exposed to nitrite ( 1.2 ± 0.03 mg L -1 ) for 96 hours. Histopathological alterations in gills, liver and kidneys observed microscopically showed damage in the tissues while gills, liver and kidneys of control groups exhibited a normal architecture. The most characteristic features observed in nitrite exposed fish were hemorrhages in the oral cavity, in gills and on fish body surface; focal hemorrhages under the liver capsule and in the stratum of parenchyma; atrophy and destructive changes of hepatocytes; granular degeneration of liver and kidney; liver hyaline-drop dystrophy . The s tudy confirmed that histopathological biomarkers of toxicity in fish organs are a useful indicator of environmental pollution.