Abstract
The catfish, Clarias gariepinus, was exposed to different acute concentrations (5-10 mg/l) of diazinon and the Lc50 value was recorded as high as 7.3 mg/l for 96 hours. The fishes exposed to three sub-lethal levels of diazinon (0.73, 1.095 and 1.46 mg/l) for 30 days showed that the pesticide induces changes in different blood parameters. Number of red blood cells (RBC), haemoglobin level and haematocrit values were elevated whereas white blood cells (WBC) count was reduced. Various blood indices like mean corpuscular volume (MCV), mean corpuscular haemoglobine (MCH) and mean corpuscular haemoglobine concentration (MCHC) vary insignificantly in the fish treated with diazinon. Glucose level and activity level of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was increased in Clarias gariepinus exposed to diazinon. Protein level in plasma of fish treated with pesticide was changed but the change was insignificant. Histological changes in the liver, gills and kidney of fishes exposed to diazinon were apparent when compared to control. Hepatocytes necrosis and bleeding were more distinct in the fishes exposed to pesticide. Glomerulus hypertrophy and bleeding in kidneys; and fusion and degeneration of secondary lamellae and epithelial hyperplasia in gills were also observed in the exposed fish.
Highlights
The catfish, Clarias gariepinus, was exposed to different acute concentrations (5-10 mg/l) of diazinon and the Lc50 value was recorded as high as 7.3 mg/l for 96 hours
The median lethal concentration (LC50) of diazinon for 96 hours computed from the Figure 1 constructed using log10 concentrations of diazinon and probit of kill was 7.3mg/l
The present results indicate that the sub-lethal exposure of diazinon to Clarias gariepinus has altered the blood parameters
Summary
The toxic discharge from industries, different mining, and agricultural developments and processing find their way to the aquatic environment and may have detrimental effects on the inhabitants (Beijer K and Jornelo, 1979; Hamilton and Mehrle, 1986). The effects of sub-lethal concentration of diazinon was measured by registering the changes in haemoglobine concentration, cell counts, haematocrit values, glucose content and enzymes (AST and ALT) activities. A control set was run with the same number of fish in same volume of water but without toxicant. The other groups of fish were exposed to three different sub-lethal concentrations (0.73, 1.095 and 1.46mg/l which are 10%, 15% and 20% of the LC50 value) of diazinon for 30 days. The liver, gills, and kidney were excised from the fishes which were sacrificed for the collection of blood. These organs were rinsed with physiological saline (0.75% NaCl) to remove the mucus and blood attached to them. The P values which were less than 0.5 considered statistically significant
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