Ciliated protists as indicators of ecosystem health: opportunities, challenges, and case studies in Italy

This communication aims to provide an overview of the outcomes and the challenges encountered in using ciliated protists as indicator of ecosystem health in the framework of several projects conducted in Italy since 2009. Ciliates (and, in general, protistan microorganisms) in spite of the key roles they play in the microbial loop, still constitute a neglected component of the biodiversity, which is rarely included in ecological risk assessment plans. Ciliates are important bacterial and fungal feeders and thus, they significantly contribute to channel nutrients up to the food web. Furthermore, numerous ciliate species can be easily cultured with a short generation time, such as those selected for the setting up of our ecotoxicological experimentation (i.e., Coleps hirtus, Euplotes aediculatus, and Rigidohymena tetracirrata). Thus, in this context, the present communication aims to highlight the usefulness of ciliates as test organisms for the development of simple and costeffective “prognostic” assays (i.e., able to detect sub-lethal toxicant effects of various environmental matrices) based on the exploitation of antioxidant responses as well as of “diagnostic” assays (i.e., able to detect overall ecosystem impairment) based on the analysis of the community structures of ciliates in arable soils to evaluate the potential impact of different agricultural managements

Shedding light on the polyphyletic behavior of the genus Sterkiella: The importance of ontogenetic and molecular phylogenetic approaches

Present study, investigates a poorly known species of the genus Sterkiella, i.e., S. tricirrata, based on two populations isolated from soil samples collected from the Colfiorito Regional Park, Umbria Region, Italy and from the Silent Valley National Park, India. Both populations showed a highly similar morphology, however different ontogenetic pattern in between. The study confirms the validity of the species S. tricirrata which was considered to be a species within the Sterkiella histriomuscorum complex. The main ontogenetic difference between S. tricirrata and other species of the genus Sterkiella is the different mode of formation of anlagen V and VI of the proter in the former. In the phylogenetic analyses, Sterkiella tricirrata clusters with Sterkiella sinica within the stylonychine oxytrichids, in a clade away from the type species (Sterkiella cavicola) of the genus Sterkiella. The study highlights the importance of ontogenetic as well as molecular data in shedding light on the polyphyletic behavior of the genus Sterkiella. A detailed description of S. tricirrata based on morphology, ontogenesis and molecular phylogenetic methods is presented. Further, the improved diagnosis has been provided for the genus Sterkiella and the poorly known species S. tricirrata

Cytotoxicity and Antioxidant Defences in Euplotes aediculatus Exposed to Single and Binary Mixtures of Heavy Metals and Nanoparticles

The aim of this study was to analyse the cytotoxicity of heavy metals (HMs) and nanoparticles (NPs) on populations of the ciliated protist Euplotes aediculatus. We used ecotoxicological tests, antioxidant assays, and the MixTOX tool in Microsoft® Excel to evaluate the toxic effect of HMs and NPs in single and binary mixtures on E. aediculatus and to detect the type of interaction between them. Based on our results, the order of toxicity was Cu > Cd >> Zn (1 h and 24 h) for HMs and ZnO > CuO>> TiO2 >> SiO2 (1 h) and CuO > ZnO >> TiO2 >> SiO2 (24 h) for NPs. The interaction between metals in binary mixtures was predominantly synergistic at low doses and antagonistic at high doses. The type of interaction depende on the metals present and their respective concentrations. Furthermore, both HMs and NPs were shown to trigger effective antioxidant responses in E. aediculatus. Our research highlights the importance of considering the combined effects of HMs and NP exposure and their potency in risk assessment

Cytotoxicity of single and bimetallic mixtures of heavy metals and antioxidant de-fenses in the soil ciliated protist Rigidohymena tetracirrata

Ciliated protists are ubiquitous eukaryotic microorganisms which are well adapted for life in soil ecosystems. Ciliates exert a key role in soil microbial food webs by mediating the fluxes of nutrients and energy between different trophic levels. Further, they promptly sense and react to various soil perturbations and toxicants. All together, this made them valuable bioindicators of soil health. In this study, we analysed the toxicity (LC20 and LC50 at 24hrs) of single metal (Cd, Cu, and Zn) and bimetallic mixtures (Cd + Zn, Cd + Cu, and Cu + Zn) and, antioxidant responses in the soil ciliate Rigidohymena tetracir-rata. The LC20 values for Cd, Cu, and Zn were 0.53, 0.22 and 23.0 mg l-1, respectively; LC50 values were 1.16, 0.37 and 32.7 mg l-1, respectively. The order of decreasing toxicity was Zn >> Cd > Cu. Analysis of the bimetallic mixture treatments using the Concentration Ad-dition (CA) model, unveiled that the Cd + Zn mixtures were able to prevalently generate antagonistic effects as compared to the other mixtures (Cd + Cu, and Cu + Zn). Antioxi-dant activities were measured in (intra- and extra-) cellular extracts using different in vitro tests. The total phenolic contents (TPC) were significantly higher in extra- Cu LC20 (p ≤ 0.01) and intra-cellular Cd LC20 extracts (p ≤ 0.001). The intra- Zn LC50 and extra- cellular Cd LC50 extracts showed significantly higher α,α-diphenyl-β-picrylhydrazyl (DPPH) scav-enging activities (p ≤ 0.05). The extra- Cd LC50 and intra-cellular Cu LC50 extracts showed significantly higher hydroxyl radical scavenging (HRSA) activities (Cd LC50 p ≤ 0.001; Cu LC50 p ≤ 0.001). Overall, R. tetracirrata seem to have a good potential to be used as test organism in ecotoxicological analysis of soil contaminated with heavy metals

Cytotoxicity and Antioxidant Defences in <i>Euplotes aediculatus</i> Exposed to Single and Binary Mixtures of Heavy Metals and Nanoparticles

The aim of this study was to analyse the cytotoxicity of heavy metals (HMs) and nanoparticles (NPs) on populations of the ciliated protist Euplotes aediculatus. We used ecotoxicological tests, antioxidant assays, and the MixTOX tool in Microsoft® Excel to evaluate the toxic effect of HMs and NPs in single and binary mixtures on E. aediculatus and to detect the type of interaction between them. Based on our results, the order of toxicity was Cu > Cd >> Zn (1 h and 24 h) for HMs and ZnO > CuO >> TiO2 >> SiO2 (1 h) and CuO > ZnO >> TiO2 >> SiO2 (24 h) for NPs. The interaction between metals in binary mixtures was predominantly synergistic at low doses and antagonistic at high doses. The type of interaction depende on the metals present and their respective concentrations. Furthermore, both HMs and NPs were shown to trigger effective antioxidant responses in E. aediculatus. Our research highlights the importance of considering the combined effects of HMs and NP exposure and their potency in risk assessment