Effects of copper and zinc on blood parameters and prediction of their recovery in Oreochromis mossambicus (Pisces : Cichlidae)

Abstract

Sublethal effects of copper and zinc on haematological parameters and their complete recovery were studied in Oreochromis mossambicus as a function of exposure time. Animals exposed to sublethal levels of copper and zinc produced a time-and dose dependent significant (P<0.05) decrease in red blood corpuscle count, haemoglobin content, oxygen carrying capacity of blood and haematocrit values, and increase in erythrocyte sedimentation rate and mean corpuscular volume and total leucocyte count. The differential count of leucocyte showed a significant (P<0.05) increase in the populations of neutrophil, basophil and lymphocyte count. The increase in these parameters was time and dose dependent. However, the percentage of thrombocytes gradually declined with increase in exposure period in all the tested concentrations. During recovery treatment, the above parameters exhibited the opposite trends. The rate of recovery or extrapolated time between day 0 to 30 of recovery period showed that RBC recorded complete recovery from Cu or Zn toxicity on days 48 or 43, 59, or 53 and 67 or 60; TLC on days 31.5 or 46.8, 36.5 or 48.5 and 42.5 or 50 in animals exposed to 100, 300 and 600 ppb Cu or Zn respectively. TLC recovered faster than the RBC count. The RBC and TLC of animals exposed to higher concentration (600 ppb) of copper and zinc took more.fime for complete recovery than anmials exposed to lower concentrations (100 or 300 ppb).