Abstract
Teleostean fish, Oreochromis niloticus was exposed to almix herbicide under field (8 g/acre) and laboratory (66.67 mg/l) conditions for a period of 30 days. Histological and ultramicroanatomical responses were investigated in stomach and intestine. In stomach, light microscopy displayed damaged Columnar Epithelial Cells (CEC) and mucosal folds, thinning of the top plate and fused mucosal folds under laboratory condition but no such significant alterations were observed except mucus secretion in field study. Electron microscopic observation revealed alterations in epithelial contour, damage in microridge structures and excessive mucin mass over epithelial surface under Scanning Electron Microscopic (SEM) study in both conditions, but the damage was more severe in laboratory study. Transmission Electron Microscopic (TEM) study disclosed severe deformed nucleus and mitochondria, cellular necrosis and severe vacuolation under laboratory study, but comparatively less symptomatic changes were observed in field study. Intestine showed damage in CEC and rupture in intestinal villi in both the conditions under light microscopy, while ultrastructural study showed degenerative changes in CEC and excess mucus secretion in laboratory condition under SEM study. TEM study depicted deformed nucleus and mitochondria, severe vacuolation, and appearance of double layered cell structures in the laboratory condition but no significant alterations were observed under SEM and TEM study in field condition. The present results clearly demonstrated comparatively less pathological lesions under field study than laboratory observations and these responses displayed by the fish species could be considered as bio indicator for evaluating herbicidal toxicosis in aquatic environment.
Highlights
Pesticides and/or herbicides are the most dangerous one to human and animals as they are present and concentrated in the food chain
Most prominent alterations in stomach of O. niloticus in the laboratory condition after almix exposure were damage in columnar epithelial cells (CEC) and mucosal folds, top plate thinning, fused mucosal folds and damage in submucosa (Figure 1.2) compared with control one (Figure 1.1), but in field condition there was slight mucus secretion from mucosa layers, and the structure mostly appeared to be normal like control condition (Figure 1.3)
Scanning electron microscopic observation showed ultra-structural lesions such as alteration of epithelial cells contour, loss and damage of micro ridge structures and appearance of mucin mass over epithelial surface under both the conditions, but the degree of responses was more severe under laboratory observation (Figures 1.4-1.6)
Summary
Pesticides and/or herbicides are the most dangerous one to human and animals as they are present and concentrated in the food chain. Use of pesticides and/or herbicides, in one hand, is a beneficial tool for crop protection from the attack of pests to increase the agricultural productivity, in other hand, is a serious concern due to its toxicity, and bioaccumulation and non-biodegradable properties [1] They are released into the environment and find their way into aquatic bodies by variety of means such as agricultural run-off, spray drift and/ or aerial spraying, and by effluent discharge from manufacturing unit. Histology is widely used as routine biomarker of xenobiotics, due to its target organ toxicity [9], while Scanning Electron Microscopy (SEM) depicts topological characterization of cell surface and Transmission Electron Microscopy (TEM) discloses the organizational orientation
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