Effects of Amorphous Silica Nanopowders on the Avoidance Behavior of Five Soil Species-A Screening Study

Silica nanoparticles (SiO₂NPs) are one of the most used in commercial products and biomedical tools, however, their environmental effects have not been fully described. Although negative effects of SiO₂NPs on the behavior of freshwater invertebrates have been reported, the knowledge is limited, especially the effect of nanopowders in terrestrial organisms. Accordingly, the aim of the present study is to understand the effects of SiO₂NPs on the avoidance behavior of five soil species, whose niche may differ thus contributing to differential harmful SiO₂NPs effects. Hence, avoidance assays testing SiO₂NPs concentrations of 0, 10, 100, 250, 500 and 1000 mg/kg were performed with Enchytraeus crypticus, Folsomia candida, Tenebrio molitor, Porcellionides pruinosus and Eisenia fetida. SiO₂NPs induced different behavioral effects, depending on the invertebrate ecology/habitat, exposure route and physiology. T. molitor, P. pruinosus and F. candida did not avoid contaminated soil; however, E. crypticus and E. fetida significantly avoided SiO₂NPs spiked soil. Since these terrestrial worms (oligochaetes) live mostly burrowed in the soil, this can provide greater opportunity for SiO₂NPs' uptake. On the other hand, the other tested organisms mainly living on the upper part of the soil did not avoid the SiO₂NPs spiked soil. The avoidance data obtained here also highlight the need for further studies to understand whether (or not) the detected behavioral responses are linked to either neurotransmission processes or sensorial aspects of the biological models.