QUANTIFIED ELEMENTAL CHANGES IN ASPIDISCA-CICADA AND VORTICELLA-CONVALLARIA AFTER EXPOSURE TO ALUMINUM, COPPER, AND ZINC

Data on metal-induced elemental changes in eukaryotic unicellular orga nisms, such as protozoa, are rare. This study focused on two species o f ciliate protozoa, Aspidisca cicada and Vorticella convallaria, both common and abundant in activated sludge. Elemental changes in cells ex posed to aluminium, copper, and zinc were determined by scanning elect ron microscopy-electron probe X-ray microanalysis. X-ray emission spec tra obtained from cells 2 h after resuspension in Chalkley's medium (c ontrol) showed clear, characteristic peaks for magnesium, silicon, pho sphorus, sulphur, potassium, um, and copper. These elements were also routinely detected in all cells resuspended in metal solution. Spectra obtained from cells treated with aluminium or zinc showed additional distinct peaks for aluminium and zinc. In copper-treated cells enhance d copper peaks were seen. Mean aluminium levels were low in A. cicada control cells (0.14 mg/g of dry weight) but higher in cells treated wi th 0.50 ppm (0.69 mg/g of dry weight) and 2.00 ppm aluminium (2.07 mg/ g of dry weight). A. cicada was ten times more sensitive to copper tha n to the other metals, and than V. convallaria. There was a significan tly higher concentration of copper in A. cicada cells treated with 0.2 0 ppm copper (2.94 mg/g of dry weight) than in control cells (2.16 mg/ g of dry weight); In A. cicada cells treated with 0.50 and 2.00 ppm zi nc significantly higher levels of zinc (2.41 and 2.07 mg/g of dry weig ht, respectively) were observed than in the control (0.41 mg/g of dry weight). After treatment with 0.50 ppm and 2.00 ppm aluminium, alumini um was significantly higher in the treated V. convallaria cells (1.58 and 0.67 mg/g of dry weight, respectively) than in control cells (0.14 mg/g of dry weight). After treatment with 2.00 ppm copper there was s ignificantly more copper in treated V. convallaria cells (3.63 mg/g of dry weight) than in controls (2.08 mg/g of dry weight). In V. convall aria cells treated with 0.50 ppm and 2.00 ppm zinc there was an increa se in the amount of zinc in cells (1.30 and 2.68 mg/g of dry weight, r espectively) compared with control cells (0.34 mg/g of dry weight). Da ta on other changes in intracellular elements in both species, after 2 h exposure to aluminium, copper, and zinc medium are given. In both s pecies, there was uptake and/or accumulation of aluminium, copper, and zinc when the external concentration of the metal was increased. Intr acellular elemental levels were altered by sublethal and toxic externa l concentrations of the metals studied. A. cicada was ten times more s ensitive to copper than to aluminium or zinc, and than V. convallaria to the metals studied.