Sensitivity to copper in a ciliate as a possible component of biological monitoring in the Lagoon of Venice

The impact of copper was studied in cultures of the microbenthic organism Euplotes vannus (Ciliophora, Hypotrichida). This ciliate was isolated from sediment collected from a particular area in the Lagoon of Venice, which may be considered almost unpolluted by heavy metals. The effects of copper exposure in the laboratory on growth, metal accumulation, total acid-soluble thiol levels, and glutathione levels were examined, together with morphological alterations. E. vannus exhibited tolerance toward copper up to a concentration exposure of 0.2 μg Cu/ml, at which cell growth rate overlapped that of controls. Copper accumulated up to 239 μg/g dry wt after exposure to 0.4 μag Cu/ml, and morphological alterations were evident in cells exposed to concentrations from this value upward. Processes of vegetative reorganization involving nuclear apparatus, membranelles, cirri, and cortex could be observed after 4 days of exposure to 0.4 μg Cu/ml. Laboratory experiments with cultures of ciliates of cosmopolitan distribution such as Euplotes species in controlled conditions indicated the value of these organisms, which constitute a simple model for a monitoring system suitable for prediction in multicellular organisms.