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Abstract Molecular data have considerably contributed to building the taxonomy of protists. Recently, the systematics of Hyalospheniidae (Amoebozoa; Tubulinea; Arcellinida) has been widely revised, with implications extending to ecological, biogeographical and evolutionary investigations. Certain taxa, however, still have an uncertain phylogenetic position, including the common and conspicuous species Nebela militaris. A phylogenetic reconstruction of the Hyalospheniidae using partial sequences of the mitochondrial Cytochrome Oxidase Subunit 1 (COI) gene shows that N. militaris does not belong to genus Nebela , but should be placed in its own genus. The morphological singularities (strongly curved pseudostome and a marked notch in lateral view) and phylogenetic placement of our isolates motivated the creation of a new genus: Alabasta gen. nov. Based on their morphology, we include in this genus Nebela kivuense and Nebela longicollis. We discuss the position of genus Alabasta within Hyalospheniidae, and the species that could integrate this new genus based on their morphological characteristics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Quadrulella (Amoebozoa, Arcellinida, Hyalospheniidae) is a genus of testate amoebae with unmistakable morphology, which secretes characteristic square plates to reinforce the test. They are mainly known from fens and freshwater habitats and have never been documented in deserts. We describe a new species, Quadrulella texcalense , from biological soil crusts in the intertropical desert of Tehuacán (state of Puebla, Mexico). Quadrulella texcalense occurred only at altitudes between 2140 and 2221 m.a.s.l., together with the bryophyte genera Pseudocrossidium, Weissia, Bryum, Didymodon, Neohyophyla and Aloina . The soil was extremely dry (moisture of 1.97–2.6%), which contrasts sharply with previous reports for the Quadrulella genus. Single cell mitochondrial cytochrome oxidase I (COI) barcoding of thirteen isolated cells showed an important morphological variability despite having all the same COI barcode sequence. Quadrulella texcalense was placed in a tree containing other Hyalsopheniidae, including a newly barcoded South African species, Q. elegans. Q. texcalense unambiguously branched within genus Quadrulella in a compact clade but with a long branch, suggesting accelerated evolution due to a transition towards a new environment and/or under-sampling. [ABSTRACT FROM AUTHOR]

We describe here a new species of sphagnicolous testate amoeba found abundantly in the forested part of the Le Cachot peatland (Jura Mountains, Neuchâtel, Switzerland) based on microscopical observations (LM, SEM). The new species, called Nebela gimlii was placed in a phylogenetic tree based on mitochondrial cytochrome oxidase sequences (COI), and branched robustly within the N. collaris complex next to the morphologically similar N. guttata and N. tincta . It is however genetically clearly distinct from these two species, and differs morphologically from them by its smaller size and stouter shape of the shell. This new species completes the phylogeny of the Nebela collaris species complex, with now eight species described, mostly from peatlands and acidic forest litter, and further demonstrates the existence of an unknown diversity within testate amoebae. Improving the taxonomy of testate amoebae in peatlands and clarifying the ecology of newly discovered species should make these organisms even more valuable as bioindicator and for palaeoecological reconstruction. [ABSTRACT FROM AUTHOR]

The existing data on the molecular phylogeny of filose testate amoebae from order Euglyphida has revealed contradictions between traditional morphological classification and SSU rRNA phylogeny and, moreover, the position of several important genera remained unknown. We therefore carried out a study aiming to fill several important gaps and better understand the relationships among the main euglyphid testate amoebae and the evolutionary steps that led to the present diversity at a higher level. We obtained new SSU rRNA sequences from five genera and seven species. This new phylogeny obtained shows that (1) the clade formed by species of genera Assulina and Placocista branches unambiguously at the base of the subclade of Euglyphida comprising all members of the family Trinematidae and genus Euglypha, (2) family Trinematidae (Trachelocorythion, Trinema, and Corythion) branches as a sister group to genus Euglypha, (3) three newly sequenced Euglypha species (E. cf. ciliata, E. penardi, and E. compressa) form a new clade within the genus. Since our results show that Assulina and Placocista do not belong to the Euglyphidae (unless the Trinematidae are also included in this family), we propose the creation of a new family named Assulinidae. Consequently, we give a family status to the genera Euglypha and (tentatively) Scutiglypha, which become the new family Euglyphidae. The evolutionary pattern suggested by SSU rRNA phylogeny shows a clear tendency towards increasing morphological complexity of the shell characterised by changes in the symmetry (migration of the aperture to a ventral position and/or compression of the shell) and the appearance of specialised scales at the aperture (in families Trinematidae and Euglyphidae). [Copyright &y& Elsevier]

Abstract: Testate amoebae (Arcellinida and Euglyphida) and diatoms (Bacillariophyta) respond to different ecological gradients. These protists are useful tools for biomonitoring and paleoecological studies in aquatic and terrestrial ecosystems. However, little is known about the responses of these microeukaryotes to soil management practices. We analyzed the testate amoeba and diatom communities from the DOK-trial (D: biodynamic, O: bio-organic, K: german ‘‘konventionell’’ integrated conventional) agricultural experiment at Therwil, Switzerland. Soil samples were collected from biodynamic and conventional plots and subsequently incubated for four months in a growth chamber. The diatom diversity tended to be higher in the biodynamic than in the two conventional systems. Redundancy analysis (RDA) suggested that diatom community structure differed between organic and the two conventional systems. Testate amoeba abundance was about five times higher in biodynamic than in conventional systems (P < 0.05) but no significant differences in diversity were reported between treatments. Altogether, these data suggest that diatoms and testate amoebae are sensitive to farming systems. As direct analyses of soil samples are time-consuming, molecular tools would be very useful for further development of the use of protists in bioindication. [Copyright &y& Elsevier]

High-throughput sequencing (HTS) of soil environmental DNA (eDNA) allows assessing the full diversity of soil micro-eukaryotes. The resulting operational taxonomic units (OTUs) can be assigned to potential taxonomic and functional identities using increasingly complete reference databases. HTS of soil eDNA is revealing a high diversity and abundance of potential eukaryovorous protists, thus challenging the paradigm of the predominantly bacterivorous function of soil phagotrophic protists (i.e. microbial loop). Using Illumina sequencing of soil eDNA and targeting the V9 region of the SSU rRNA gene, we investigated the taxonomic and functional diversities, distribution and co-occurrence patterns of soil micro-eukaryotes in three land-use categories: forests, meadows and croplands located in Switzerland. Each OTU was assigned to a broad functional category (phototrophs, phagotrophs, osmotrophs, or parasites). Total OTU richness was similar in the three land-use categories, but community composition differed significantly between forests and other land-uses. The proportion of fungal sequences (especially Basidiomycota) was highest, and phototroph (i.e. soil microalgae) sequences least abundant in forests. Seven OTUs representing phagotrophic protists, together accounting for >25% of all phagotroph sequences, were significantly correlated to the total number of phototroph sequences, thus suggesting algivory. At least three of these OTUs corresponded to known algal predators. These results suggest that beyond plants, soil microalgae represent a functionally significant but rarely considered input of carbon in soils that should be taken into account when modelling soil nutrient cycling. [ABSTRACT FROM AUTHOR]

Transfer functions are valuable tools in palaeoecology, but their output may not always be meaningful. A recently-developed statistical test (‘randomTF’) offers the potential to distinguish among reconstructions which are more likely to be useful, and those less so. We applied this test to a large number of reconstructions of peatland water table depth based on testate amoebae. Contrary to our expectations, a substantial majority (25 of 30) of these reconstructions gave non-significant results (P > 0.05). The underlying reasons for this outcome are unclear. We found no significant correlation between randomTF P-value and transfer function performance, the properties of the training set and reconstruction, or measures of transfer function fit. These results give cause for concern but we believe it would be extremely premature to discount the results of non-significant reconstructions. We stress the need for more critical assessment of transfer function output, replication of results and ecologically-informed interpretation of palaeoecological data. [ABSTRACT FROM AUTHOR]