Arsenic induced toxicity and histopathological changes in gill and liver tissue of freshwater fish, tilapia (Oreochromis mossambicus).

Acute toxicity of arsenic to tilapia (Oreochromis mossambicus) and its histopathological impacts on gill and liver tissue were evaluated. The median lethal concentration (96 h; LC50) of arsenic (NaAsO₂) was calculated as 28.22 ppm in repeated semi static test method. Fish were exposed to 3 ppm, 28 ppm and 56 ppm concentrations of NaAsO₂ and gill and liver samples were collected after 48 h, 96 h and 192 h of exposure. The changes in gill were characterized by epithelial hyperplasia, epithelial lifting and oedema, lamellar fusion, aneurism, desquamation and necrosis, whereas, the liver tissue showed focal lymphocytic and macrophage infiltration, congestion, vacuolization and shrinkage of hepatocytes, dilation of sinusoids, cloudy swelling, vacuolar degeneration, focal necrosis and nuclear hypertrophy. The result showed that acute arsenic toxicity severely affects the normal behavior and vital organs which is deleterious for the exposed fish.