Changes in the hematology of the freshwater fish, Channa punctatus (Bloch) exposed to the toxicity of deltamethrin

The freshwater fishes are an important source of animal protein to human population. They are adversely affected by aquatic pollutants such as pesticides used in agriculture, which are easily washed off into the water bodies. The effect may be direct when the pesticide is absorbed into the body through the skin, gill, intestine, wound, etc. It may be indirect when the pesticide alters the quality of the water, such as depletion of dissolved oxygen. The aim of this study was to evaluate the changes in some hematological parameters of the fresh water fish Channa punctatus exposed to lower (0.075 mg/l) and higher (0.15 mg/l) sub lethal concentrations of LC50 (0.75mg/l) of the synthetic pyrethroid pesticide deltamethrin for 15, 30 and 45 days. In the fish exposed to both the concentrations for 45 days there was a significant decrease in the hemoglobin content, total erythrocyte count, packed cell volume, mean corpuscular volume, mean corpuscular hemoglobin concentration, as compared to the respective control fish. On the other hand, there was a significant increase in the total leukocyte count, mean corpuscular volume, erythrocyte sedimentation rate, and clotting time values during 30 and 45 days of exposure in lower and higher concentrations of deltamethrin. The differential leukocyte count in fish of 30 and 45 day test period showed a significant increase in the populations of lymphocytes, neutrophils and eosinophils, and significant decrease in monocyte and basophil populations. There was significant reduction in the mean length, breadth and area of erythrocytes in these deltamethrin exposed fish. The result of this study reveals that the synthetic pyrethroid pesticide deltamethrin adversely affects the hematology of the freshwater fish Channa punctatus, and calls for the limited and cautious use of highly toxic pesticides like deltamethrin.