M.Sc. (Zoology) / Tilapia sparrmanii (Smith) was exposed to sub-lethal doses of chromium, manganese, zinc and iron for 96 hours at an acidic pH (5), a physiological pH (7,4) and an alkaline pH (9), as well as a prolonged exposure (2 - 4 weeks) at an uncontrolled pH. In the laboratory fish were kept in aquaria which were supplied with continuously flowing borehole water. Controlled laboratory conditions existed during experimentation. Blood and liver samples of the experimental fish were sampled after exposure. The bioconcentration and the effect of the selected metals at the mentioned conditions, were thereby determined on bloodcoagulation, total and differential leucocyte counts, and liver enzYmes to investigate the possible damage to the liver. As metals have the ability to enter and concentrate in the body, the bioconcentration of each metal was determined by atomic absorption sPectrophotometry in the blood and liver. Chromium showed an increase in concentration in both the blood and liver, with an increase in pH after short term (96h) exposure. The statistical significant increases of manganese concentration in the blood over a short term were not reflected in the liver. It may be indicative of homeostatic control. A similar phenomenon was found with .zd.nc , The concentration of zinc in the liver did not reflect the progressive decrease in the blood wi th a increase in pH. Iron revealed a statistical significant increase in bioconcentration in the liver with, an increase in pH, which is indicative of the activity of the liver. The long term exposure of fish to chromium and manganese caused a significant increase in the concentration of the metals in the blood and liver. The only significant increase in concentration after exposure to iron, occured . in the Iiver. Exposure to zinc however caused a statistical significant decrease in concentration in both the blood and liver. Differential leucocyte counts reflected lymphocytosis, eosinophilia, monocytopenia and neutropenia, after short term exposure. These conditions nearly always resulted in leucopenia. Long term exposure to manganese and zinc reflected both eosinophilia and neutropenia. Chromium reflected eosinophilia, and iron, neutropenia. The only statistically significant change in the number of leucocytes after long term exposure, was caused by zinc and resulted in leucopenia. According to the photokymographic observation of blood coagulation by the thrombelastograph, exposure to the selected heavy metals lead to a prolonged clotting time and thrombocytopenia. Long term exposure (4 weeks) to manganese caused another bleeding disease, called hemophilia. It was thus evident that the exposure to heavy metals led to clotting defects, which caused bleeding.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:11777 |
| Date | 23 July 2014 |
| Creators | Gey van Pittius, Marina |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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