Toxic effects of single and combined metals at the individual and population level of C. elegans
5 February 2019
Campus Middelheim, A.143 - Middelheimlaan 1 - 2020 Antwerpen (route: UAntwerpen, Campus Middelheim
Organization / co-organization:
Department of Biology
R. Blust, S. Husson & G. Baggerman
PhD defence Sofie Moyson - Faculty of Science, Department of Biology
Industrial and natural sources of heavy metals cause an increase in metal accumulation, which can lead to serious health hazards for diverse animals including humans, resulting in a persistent (eco)toxicological concern. Although metals (mainly) occur in mixtures in natural environments, metal effects are usually studied for each metal separately. Metal mixture studies are therefore necessary to provide a solid scientific basis for setting standards for environmental protection and risk assessment. Furthermore, metal effects can be studied from the molecular to the population level and beyond. Combining effects at different organisational levels is necessary to better understand the observed toxicity.
Therefore, the aim of this study was to gain insights into the sensitivity to the selected single metals (Cu, Cd, Zn), and to investigate whether and how toxicity changes in mixtures. To assess different endpoints (mortality, locomotion, chemosensation, body length and population size), we fully exploited the benefits of the nematode Caenorhabditis elegans to investigate the toxic metal effects at different organisational levels (molecular, individual and population). Finally, the bioavailability and accumulation of these metals in the body of C. elegans were linked to the observed toxic effects.
Our study showed that most mixtures had a stronger toxic effect than the constituent single metals, resulting in additive or synergistic effects for the ZnCu, CuCd and ZnCuCd mixtures, while metals in the mixture ZnCd acted antagonistically depending on the Zn concentrations used.
The toxic results were better understood when effects on different endpoints at different levels were combined. For example, similar trends were observed for different endpoints but they were more pronounced at one level than at another. Similarly, no metal effect was observed at the molecular level, although clear effects were noticed at the individual and population level. Some parameters also seemed to be more sensitive than other parameters measured under the same conditions. For example, metal toxicity was more pronounced in terms of locomotion than of mortality and chemosensation for short-term studies at the individual level, while it was more evident on population size than body length for long-term studies at the population level.
Our findings showed that free metal ions and hence the waterborne uptake route was identified to be the best predictor for body burdens of both single metals and mixtures and for toxicity of single metals.