| Summary: | M.Sc. (Zoology) === Tilapia sparrmanii (Smith) obtained from the Provincial Fishery in Lydenburg was used for toxicological studies. The haematology of T. sparrmanii was investigated after exposure to sub-lethal doses of atrazine, zinc and iron for 72 hours in a continuous flow and static system, as well as prolonged (4 weeks) exposure in the continuous flow system. After exposure the blood of the experimental fish were sampled. Mean values and standard errors were obtained for several haematological parameters such as number of red and white blood cells, haematocrit, haemoglobin, mean corpuscular volume, pH, plasma glucose-, protein-, lipid- and lactate concentrations, as well as plasma Na+, K+, eland Ca+. Statistically significant differences were found between the values of haematological parameters of experimental and control fish. A tendency towards haemoconcentration was observed when fish were exposed to the low pollutant concentrations, while signs of haemodilution was found at higher concentrations. The results in this study demonstrate that, after prolonged exposure, T. sparrmanii develops a tolerance and partially recovers from the stress condition. The bioconcentration of atrazine in the blood of T. sparrmanii after exposure were determined by liquid chromatography and zinc and iron by atomic absorption spectrophotometry. During this study it was found that atrazine, zinc and iron concentrated in the blood of T. sparrmanii after short- and prolonged exposure to the pollutants. The routine oxygen consumption of "!'. sparrmanii exposed to atrazine, zinc and iron were determined in a continuous flow apparatus over 72 hours. The oxygen consumption of the experimental fish fluctuated for the first 8-12 hours during the acclimation period. The influence of atrazine on the routine oxygen consumption was not so drastic as that of zinc and iron. Zinc caused a decrease in the routine oxygen consumption of the experimental fish over 72 hours, while iron increased the routine oxygen consumption...
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