Haematological Profile of Oreochromis Niloticus (Burchell, 1822) Exposed to Cadmium Chloride

Changes in Oreochromis niloticus blood cells were investigated after 96-h of exposure to cadmium chloride. One hundred and eighty (180) Oreochromis niloticus with average weight of 26.07±1.23g and mean length of 17.50 + 0.50cm were divided into 5 groups (T1-T5) at ten (10) fish per group and in triplicates after being acclimatized for 14 days. They were then exposed to various concentrations (0, 28, 30, 32, 34 and 36 mg/l) of cadmium chloride. The packed cell volume (PCV) of the treatments decreased significantly relative to that of the control, while their platelet counts increased compared with the control. There was also a reduction in the RBC (2.70, 2.51, 2.24, 1.98, 1.64 and 1.22) of treatments. Other blood parameters did not vary significantly in comparison with the control group, but it is worth noting that, the mean corpuscular volume (MCV) (70.78, 76.09, 83.71, 90.55, 105.49 and 128.68fL), mean corpuscular haemoglobin (MCH) (24.66, 24.49, 27.37, 29.83, 33.14 and 42.18pg) and mean corpuscular haemoglobinconcentration (MCHC) (34.83, 32.19, 32.71, 32.95, 34.41 and 34.78%) increased considerably in all treatments compared to the control. These alterations have been attributed to direct or feedback responses of structural damage to RBC membranes resulting in haemolysis and impairment inhaemoglobin synthesis, stress related release of RBCs from the spleen and hypoxia, which was induced by exposure to cadmium chloride. This study therefore gives an insight into toxic effect of cadmium chloride on fish.