Development of a new ecotoxicological assay using the testate amoeba Euglypha rotunda (Rhizaria; Euglyphida) and assessment of the impact of the herbicide S-metolachlor

Abstract

An ever-increasing diversity of potentially toxic chemical compounds are being developed and released into the environment as a result of human activities (e.g. agriculture, drugs, and cosmetics). Among these, pesticides have been shown to affect non-targeted wildlife since the 1960s. A range of ecotoxicological tests are used to assess the toxicity of pesticides on various model organisms. However most model organisms are metazoans, while the majority of Eukaryotes are unicellular microorganisms known as protists. Protists are ubiquitous organisms of key functional roles in all ecosystems but are so far little studied with respect to pesticide impact. To fill this gap, we developed a new ecotoxicological test based on Euglypha rotunda, a common soil amoeba, grown in culture flask with Escherichia coli as sole food source. We tested this assay with the herbicide S-metolachlor, which is known to affect cell division in seedling shoots and roots of weeds. Reproducible growth conditions were obtained for E. rotunda. The growth of E. coli was not affected by the herbicide. The growth of E. rotunda was affected by the herbicide in a non-linear way, growth being significantly reduced at ca. 15 μg/L, but not at 150 μg/L. Our results show the potential for using soil protists in ecotoxicology and adds to the growing body of evidence for non-linear impacts of pesticides on non-target organisms. With the acquisition of additional data, the protocol should be suitable for standard ecotoxicological tests.

Assessing the ecological value of small testate amoebae (<45 μm) in New Zealand peatlands

“…Testate amoebae are a polyphyletic assemblage of freeliving single-celled shelled eukaryotes . Molecular phylogenetic studies based on ribosomal RNA and protein gene sequences show that these organisms belong to the three supergroups Amoebozoa (Nikolaev et al, in peatlands (Beaulne et al, 2018), as a tool for monitoring restoration success Valentine et al, 2013), and as indicators in ecotoxicology (Amacker et al, 2018;Meyer et al, 2012). They have also been applied as trace evidence in forensic science (Swindles and Ruffell, 2009), and for defining post-mortem intervals (Seppey et al, 2016;Szelecz et al, 2014).…”

Carboxylic Acid Derivatives in Herbicide Development

“…The lack of VLCFAs results in the drop of various lipids in plant cells, such as triacylglycerols, sphingolipids, and cuticles . Many other physiological activities, such as cell division, cell damage, and growth of the plant germ and root, can also be affected through the inhibition of VLCFA formation in plants . Therefore, VLCFA inhibiting herbicides have been used as soil treatment reagents for weed control.…”

“…124 Many other physiological activities, such as cell division, cell damage, and growth of the plant germ and root, can also be affected through the inhibition of VLCFA formation in plants. 125 Therefore, VLCFA inhibiting herbicides have been used as soil treatment reagents for weed control. Amide herbicides, which have been used as herbicides in wheat, rice, corn, and soybean fields for decades, have been considered as inhibitors of VLCFA biosynthesis.…”

The Swiss Ecotox Centre: bridging the gap between research and application

“…Two laboratory bioassays, a reproduction test with collemboles, and a behavioral test with earthworms, were applied in the project “Ecotoxicity of biocide-containing facade renders” (Vermeirssen et al submitted), and for testing the effects of wood preservatives on soil organisms [ 5 ]. The Ecotox Centre has also contributed to the development of an ecotoxicity testing method using soil protists [ 1 ].…”