Gill damage in Oreochromis mossambicus and Tilapia sparrmanii after short-term copper exposure

Abstract

Oreochromis mossambicus and Tilapia sparrmanii were exposed to 600 μg L −1 and 4.4 mg L −1, respectively, of waterborne copper for 24 h. The arithmetic mean thickness of gill epithelium ( H ar), using a morphometric technique, was measured after 4 and 24 h of exposure for both fish species. Copper exposure caused the arithmetic thickness of gill epithelium in O. mossambicus to increase to 4.92±0.210 μm, after 24 h of exposure, which was significantly higher than the corresponding control value of 2.97±0.131 μm and that of the 4 h exposure value (3.08±0.142 μm), while the 4 h exposure value did not differ from the control values. The gill epithelial thickness of 6.07±0.156 μm for T. sparrmanni exposed to copper was already significantly higher than the control value of 4.96±0.205 μm after only 4 h of exposure. The increase in epithelial thickness remained during the entire 24 h of exposure, with the value for the exposed fish after 24 h (5.56±0.190 μm) being significantly higher than that of the control fish (4.99±0.137 μm).