'N Vergelykende ondersoek na die invloed van kopersulfaat op vier geselekteerde varswaterslakspesies

Abstract

In this study the effect of copper sulphate exposure on some freshwater snails was investigated. Four species were selected for this investigation. Two containing haemoglobin viz. Biomphalaria glabrata, Helisoma duryi, and the other two, Lymnaea stagnalis and Lymnaea natalensis containing haemocyanin. In all the tests the snails were exposed to pre-determined concentrations of copper sulphate in order to ascertain its general toxicity (LD5o), accumulation in the haemolymph, the soft tissue and the shell. Furthermore, depuration of copper sulphate was tested and ultrastructural damage to the soft tissue was investigated. Finally, the effect of copper sulphate on egg production as well as hatching was studied. Although copper sulphate was in general toxic to all the species employed, there were no clear cut differences between the species containing haemoglobin and haemocyanin. However, this study showed that L. natalensis, compared to the other species employed, was markedly vulnerable to copper sulphate exposure. Accumulation of copper was detected in the soft tissue of all the species tested, however, an increase in the copper concentration of the shells was observed in H. duryi and L. natalensis only. During exposure the copper levels in the haemolymph varied, and therefore it was impossible to draw any conclusions from these results. The results of this study clearly showed that copper was released by all the species after exposure. In the case of L. natalensis the release was less profound, and thus explain why this species is so sensitive to copper sulphate exposure. Electron micrographs of all the exposed specimens revealed that large vacuoles were present in the basal part of their surface epithelial cells. Although copper sulphate had no effect on the egg production of B. glabrata and L. natalensis, it impaired the embryo development as well as hatching of the eggs.