Gill damage, metallothionein gene expression and metal accumulation in Tilapia sparrmanii from selected field sites at Rustenburg and Potchefstroom, South Africa
Fish were collected from field sites in the mining and agricultural areas of Potchefstroom and Rustenburg, North-West Province, South Africa. Water and sediment samples from each site, together with fish muscle and gills, were analysed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for Li, Na, Mg, Al, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb and U. All metal levels were within the levels set by the South African Department of Water Affairs and Forestry, except for copper, which was still within the levels set by other guidelines. Water hardness, pH, dissolved oxygen concentration and conductivity were measured at each site. Fish gills were analysed morphometrically for arithmetic mean epithelial thickness (Har) and with Reverse Transcriptase PCR for metallothionein (MT) gene expression levels. Fish liver was also analysed for MT expression. Har was found to increase with changing copper levels in gills of fish, while gill and liver MT levels corresponded to changes in sediment and gill cadmium levels, respectively. There were highly significant differences in Har between different sampling sites, while no significant differences in gill and liver MT expression were found.