Mixture Effects of Copper, Cadmium, and Zinc on Mortality and Behavior of Caenorhabditis elegans

The toxicity effects of zinc (Zn), copper (Cu), and cadmium (Cd), both as single metals and in combination, were examined in the nematode Caenorhabditis elegans. Metal effects on lethality were analyzed in a time-dependent manner using different concentrations in K-medium. To investigate the effects on locomotion and chemosensation, lethal concentration at 20% (LC20) values were used. The results showed that Cu toxicity was higher compared with Cd and Zn, resulting in higher mortality rates and a more reduced locomotion. Lethality increased over time for all metals. When Cd was added to Cu, 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 Cd, while in combination with Cu, 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 Zn seemed to have a neutral effect. After LC20(24h) exposure, reduced crawling speed (except for Zn) and reduced thrashing behavior (except for Zn and the ZnCd mixture) were observed. Almost no significant effects were observed on chemosensation. Because the same trend of mixture effects was noted in locomotion and in lethality tests, locomotion can probably be considered a sensitive endpoint for metal toxicities. (C) 2017 SETAC