Acute toxicity bioassay of Malathion (EC 50%) on the fish, Oreochromis mossambicus (Tilapia) and associated histological alterations in gills

In the present study, the freshwater fish, Oreochromis mossambicus were exposed to five different acute concentrations of Malathion like 0.626, 1.252, 2.503, 5.006 and 10.012 ppb for 96 hrs. The 96 h LC50 of Malathion for O. mossambicus was determined to be 0.5925±0.0625 ppb MAL/l. In addition, the study aimed to investigate the histopathological alterations of acute concentrations of Malathion in the gills. The most common histopathological changes in the gills of fish exposed to Malathion were characterized by thickening of secondary lamellae, hemorrhage at primary lamellae, epithelial lining in the tips, lamellar aneurysm, lifting up of epithelium, deformation of the cartilage core, erosion of secondary lamellae, cartilage tissue hypertrophy, shortening of the secondary lamellae, blood congestion in the secondary lamellae and curling of secondary lamellae. Ultimately, the study revealed that the degree of distortion of the gill was in proportion to the duration of exposure and concentration i.e., dose and time dependent.