Blood dyscrasia in a teleost, Colisa fasdatus after acute exposure to sublethal concentrations of lead

Colisa fasciatus , a freshwater teleost, were exposed for 90-h to 15 mg l⁻¹ (0.79 of the96-h LC₅₀ value) lead nitrate under static test conditions. The treatment resulted in decreased ( P≤ 0.001) erythrocyte counts, haematocrits and haemoglobin contents of the moribund fish. Toxicity of the metal was also characterized by significant ( P <0.001) acceleration in erythrocyte sedimentation rate, numerical increase in the number of immature erythrocytes in circulation, lysis and degeneration of erythrocytes, and an increase in the hepatosomatic index. Leucocyte and thrombocyte counts, the number of lymphocytes, and blood clotting times were not significantly different between experimental and control fish. Haemolytic anaemia and an overt increase of circulating immature erythrocytes can be used in monitoring lead poisoning in fish.