Dose and Time-Related Pathological and Genotoxic Studies on Thiamethoxam in Fresh Water Fish (Labeo rohita) in Pakistan

A total of 60 fresh-water fish were obtained from a local fish breeding center and carefully transported in plastic bags having adequate amount of oxygen and water. After 7 days of acclimatization, all the fish were randomly divided and kept in five equal groups (A-E). The experimental fish were exposed to various concentrations (0, 0.5, 1.0, 1.5 and 2.0 mg/L) of thiamethoxam for a period of 120 h. Blood and other tissue samples of each treated fish were collected after 72, 96 and 120 h. Various physical responses like operculum and bouncing movement, mucus secretion, darkening of fins, fin tremors, swimming in isolation on one side, surface breathing and erratic swimming were observed in fish treated with higher concentrations. Results indicated that the values of red blood cell counts (RBCs), packed cell volume (PCV) and hemoglobin (Hb) concentrations were significantly lower and white blood cell (WBCs) and neutrophil counts increased significantly in thiamethoxam treated fish as compared to unexposed fish. The frequency of various nuclear (micronuclei, erythrocytes with nuclear remnant, erythrocytes with condensed nuclei and erythrocytes without nucleus) and morphological changes (leptocytes, stomatocytes, dividing erythrocytes and tear shape erythrocyte) intreated fish was significantly higher as compared to control group. Microscopic analysis of gills tissues of various experimental fish exhibited atrophy of secondary lamellae, pyknosis of lamellar epithelial pillar cells, lamellar degeneration, congestion, aneurysm and curling of lamellae. (C) 2019 PVJ. All rights reserved