Histopathological and haematological response of male rainbow trout (Oncorhynchus mykiss) subjected to butachlor

Abstract

This study was aimed at assessing the histopathological and haematological effects of a widely used herbicide on rice paddy fields, i.e. butachlor, on rainbow trout. Fish were exposed to butachlor at a concentration of 0.39 mg/l, for a period of 10 days. Haematologically, fish showed a significant decrease in erythrocyte count, haemoglobin, white blood cells and lymphocytes and a significant increase in neutrophils compared to controls (P < 0.05). Histopathological observations of prepared sections of the treatment group also revealed pathological lesions of varying severity in studied organs, including liver (hyperaemia and haemorrhage, bile duct hyperplasia, dilated sinuses, interstitial oedema, monocellular necrosis, nuclear degeneration and hypertrophy in hepatocytes), gills (hyperplasia and hyperplasia of lamellar epithelium, fusion of lamellae, rod-like structures of secondary gill lamellae, cystic-like lesions) and kidneys (vacuolar degeneration of tubular epithelium, desquamation of epithelium and necrosis of tubular epithelium). It is concluded that butachlor caused changes in certain haematological parameters and histopathologically, exerted destructive effects on the gills, liver and kidneys of rainbow trout.