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

Oreochromis mossambicus and Tilapia sparrmanii were exposed to 600 mu g 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 mu m, after 24 h of exposure, which was significantly higher than the corresponding control value of 2.97 +/- 0.131 mu m and that of the 4 It exposure value (3.08 +/- 0.142 mu m), while the 4 h exposure value did not differ from the control values. The gill epithelial thickness of 6.07 +/- 0.156 mu m for T. sparrmanni exposed to copper was already significantly higher than the control value of 4.96 +/- 0.205 mu m 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 mu m) being significantly higher than that of the control fish (4.99 +/- 0.137 mu m). (c) 2004 Published by Elsevier B.V.