Ecotoxicity responses of ciliates Paramecium bursaria to trace metals and rare-earth elements

ABSTRACT

The use of trace rare metals and rare-earth elements (REEs) in diverse areas of the world economy (e.g. agronomy, medicine, industry) has significantly increased during the last decades. At present, the information on the ecotoxicological effects of these elements is scarce and contradictory. This study aims to evaluate the ecotoxicity of 15 REEs (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu) and 3 trace rare metals (Ga, Ge, and In) to ciliates Paramecium bursaria, which are a symbiosis of Paramecium and green algae Chlorella. Median lethal concentrations (12-h LC₅₀) were assessed in P. bursaria cells at 12 h of exposure. A bioassay method based on galvanotaxis was used to explore the toxicity of non-lethal concentrations of cerium chloride to P. bursaria cells. The results showed a significant inhibition of galvanotactic migration of P. bursaria by CeCl₃ in the presence of an electric field. This preliminary work aimed to evaluate the sensitivity of P. Bursaria to trace metals and REEs.

KEYWORDS:

• Rare-earth elements
• bioassay
• galvanotaxis
• Paramecium bursaria

Acknowledgments

The authors are grateful for helpful comments from the anonymous referees towards the improvement of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).