Histopathological and ultramicroscopical changes in gill, liver and kidney of Anabas testudineus (Bloch) after chronic intoxication of almix (metsulfuron methyl 10.1%+chlorimuron ethyl 10.1%) herbicide

• Effects of almix on fish model both in laboratory and field conditions.
• Almix caused histopathological lesions in cellular and subcellular layers.
• Identification of biomarkers against herbicidal toxicosis.

Present study aimed to investigate the effects of almix herbicide on histopathological and ultrastructural changes in freshwater teleostean fish, Anabas testudineus (Bloch) under field and laboratory conditions with a dose of 8 g/acre and 66.7 mg/L respectively for 30 days. In field experiment fish species were reared in special type of cage submerged in pond. Cellular alterations of the concerned organs namely gills, liver and kidney were observed through light, scanning and transmission electron microscopy (SEM and TEM). Gill showed hypertrophy and oedema in secondary gill epithelium, and epithelial lifting under laboratory condition but in field condition hyperplasia was prominent. SEM study revealed necrosis, hyperplasia, excessive secretion of mucus and loss of microridges; while TEM study depicted degenerative changes in mitochondria and chloride cells and severe cytoplsmic vacuolation but the changes were comparatively less under field study. In liver, damage in acinar cells of hepatopancreas, degenerative changes in zymogen granules and detachment of hepatopancreatic acinar cells under laboratory condition were the serious changes, but in field condition fatty deposition is prominent. TEM study depicted dilated, degranulated and vesiculated rough endoplasmic reticulum, dilation and swelling of mitochondria and vacuolation in hepatocytes, but under field condition dilation of mitochondria and appearance of vacuolation were well marked. Kidney showed shrinkage of glomerulus, damaged and hypertrophied proximal convoluted tubule, loss of haematopoietic tissues under light microscopy; while ultrastructural changes like degenerative changes in mitochondria, deformed nucleus, dilation, fragmentation and vesiculation of rough endoplasmic reticulum, severe vacuolation in cytoplasm and necrosis were of very serious concern under laboratory condition, but in field condition epithelial cells showed less damage. Responses depicted that symptoms of lesions were more pronounced under laboratory than field condition and the degree of responses in different tissues were different under these two conditions. Therefore, evaluation of these histopathological lesions in concerned tissues may be established as symptomatic indicators for toxicity study in aquatic ecosystem.