Mixture effects of copper, cadmium and zinc on mortality and behaviour of **C. elegans**

In this study toxicity effects of zinc, copper and cadmium, both as single metals and in combination, were examined for the nematode Caenorhabditis elegans. Metal effects on lethality were analysed in a time-dependent manner using different concentrations in K-medium. LC20 concentrations were used to investigate the effects on locomotion and chemosensation. The results showed that copper toxicity was higher compared to cadmium and zinc, resulting in higher mortality rates and a more reduced locomotion. For all metals lethality increased over time. When cadmium concentrations were added to copper, and vice versa, significant increases in toxicity were noted. Different interaction effects were observed for the mixtures ZnCd, ZnCu, CuCd and ZnCuCd. Zinc seemed to have a neutral toxic effect on cadmium, while in combination with copper, a similar additive effect was seen as for the CuCd combination. Binary and tertiary metal mixtures caused a strong decrease in locomotion, except for the ZnCd combination, where zinc seems to have a neutral effect. After LC2024 h exposure, a reduced crawling speed, except for zinc, and a reduced thrashing behaviour, except for zinc and ZnCd mixture were observed. Almost no significant effects were observed on chemosensation. Since the same trend of mixture effects was noted in locomotion and in lethality tests, locomotion could probably be considered as a sensitive endpoint for metal toxicities.