Abstract
M.Sc. (Zoology)
A number of chemical substances in mining, industrial, agricultural and domestic effluents are likely to contaminate watercourses. These toxicants have a definite effect on all aquatic life, even at sublethal concentrations. Due to the extensive copper mining activities in the Phalaborwa region, there is concern that the sublethal effect of copper might affect the physiology of fish in the Olifants River, Kruger National Park, Transvaal. Copper can be found as an essential micronutrient in nearly all waters, although anthropogenic sources such as metals from mining and planting industries might produce environmental concentrations causing toxic effects to fish. Several effects of exposure to sublethal concentrations of copper have already been reported in fish,
In the present study, the blood coagulation, general haematology, osmoregulation and
differential white blood cell counts of the Mozambique tilapia, Oreochromis mossambicus were investigated after the exposures to sublethal concentrations of copper, for a short-term (96 hours) exposure as well as a long-term (four weeks) exposure in experimental flow through systems, at both 29 ± I°C and 19 ± I°C.
After the respective sublethal exposures, changes in the values of blood coagulation, general haematology, osmoregulation and differential white blood cell counts were obtained, to determine the effects of the chosen copper concentrations on the blood physiology of O. mossambicus, at 29 + 10 and 19 ± I°C, respectively.
After a photographic observation of blood, during all the phases of coagulation was
made, it was evident that the exposure to copper, at both temperatures, resulted in delays of the blood coagulation times as well as decreases in the elasticity of the clots that formed. Copper was found to induce haemophilia at 29 ± I°C and 19 ± l°C. whilst at 19 ± I°C it also induced thrombocytopenia. Thus exposure to copper lead to coagulation defects which caused haemorrhage which can eventually cause the death of these fish...