Abstract
Present study aimed to investigate the effects of glyphosate-based herbicide, Excel Mera 71 on histopathological and ultrastructural changes in freshwater teleostean fish, Anabas testudineus (Bloch) under field (750 g/acre) and laboratory (17.20 mg/l) conditions for 30 days. In field experiment, fish were reared in special type of cage submerged in pond. Cellular alterations in stomach and intestine were observed through light, scanning and transmission electron microscopy (SEM and TEM). Lesions at the cellular and subcellular levels under field and laboratory conditions were compared. Responses under light microscopy depicted that the symptoms of lesions were more pronounced under laboratory condition than field. Ultrastructural examination also confirmed the observations through SEM and TEM study and the degree of responses in concerned tissues were different under these two conditions. Therefore, evaluation of these histopathological lesions in the concerned tissues may be established as symptomatic indicators for toxicity study in aquatic ecosystem.
Highlights
Aquatic pollution by pesticides and/or herbicides, either through run-off from agricultural land, or by direct applications such as spray drift, aerial spraying and by discharge as effluents from manufacturing industries, is recognized as strong biological poisons
Fish were divided into two groups: one group was transferred to field ponds located at Crop Research and Seed Multiplication Farm (CRSMF) premises of the University of Burdwan and other group was transferred to departmental laboratory aquarium
The most prominent lesions identified by light microscopic study in intestine of A. testudineus were degenerative changes in columnar epithelial cells and lamina propria, and disruption of blood vessel which led to damage in lamina propria under laboratory condition (Figure 2.2), but in field condition the extent of damage was comparatively less which included only secretion of mucus by exocytosis in some places of mucosal layer (Figure 2.3)
Summary
Aquatic pollution by pesticides and/or herbicides, either through run-off from agricultural land, or by direct applications such as spray drift, aerial spraying and by discharge as effluents from manufacturing industries, is recognized as strong biological poisons. Glyphosate is the most effective modern third generation, broad-spectrum herbicide and widely used both in agriculture and paddy-cum-fish-culture system in recent times. It is a non-selective, cost- effective and post-emergence herbicide [2]. Glyphosate is a weak organic acid; its chemical name is N-(phosphonomethyl) glycine. Glyphosate is soluble in water (12 g/l at 25oC) but insoluble in most organic solvents [3]. Glyphosate is readily degraded both from water and soil by soil microbes to aminomethylphosphonic acid (AMPA) and carbon dioxide (CO2) [4]. Due to strong adsorptive characteristics, glyphosate and AMPA are not likely to move to groundwater but have the potency to contaminate surface water. Glyphosate is in the toxicity class of III (on I to IV scale, where IV is least dangerous) for oral and inhalation exposure [5]
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