We isolated and cultivated 31 strains of free-living heterolobosean flagellates and amoebae from freshwater, brackish, and marine sediments with low concentrations of oxygen. Phylogenetic analysis of ...small subunit (SSU) rDNA showed that the strains constitute a single clade, the Psalteriomonadidae. According to combined light-microscopic morphology plus molecular phylogeny, our isolates belong to seven species and five genera, from which three species and two genera are new. In addition, previously described anaerobic species Percolomonas descissus and Vahlkampfia anaerobica are transferred to the Psalteriomonadidae. We identified a flagellate stage of Monopylocystis visvesvarai which was reported to produce only amoebae. Two environmental sequences previously obtained from acidic environments belong to the Psalteriomonadidae as well, suggesting a broad ecological importance of the Psalteriomonadidae. The ultrastructure of two psalteriomonadid species was also studied. Unifying features of the Psalteriomonadidae are acristate mitochondrial derivates, flagellates with a ventral groove and four flagella, and a harp-like structure in the mastigont. A new overall classification of the Psalteriomonadidae is proposed. Our data show that the Psalteriomonadidae are much more diverse than previously thought and constitute the main anaerobic lineage within the Heterolobosea.
This study deals with the chronology of the largest long-runout landslide in the northwesterrn part of the Western Flysch Carpathians (Kysucké Beskydy Mts, Slovakia). Despite the impossibility of ...using direct radiocarbon dating method, time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological/geomorphological elements situated on and adjacent to the landslide body. The results show that the landslide evolved between ∼
10.3 and 9.0
ka
14C BP, i.e. in the wider transitional phase between the Late Glacial (LG) and the Holocene. The main mass movement activity took place at the turn of the Younger Dryas/Preboreal chronozones, whereas retrogressive activity continued up to the Preboreal/Boreal transition. Radiocarbon dating together with pollen analysis and sedimentology of landslide-dammed palaeolakes and colluvial peat bogs revealed almost continuous Holocene palaeogeographical records between ∼
10.3 and 3.3
ka
14C BP. Periods of enhanced sediment supply to the reservoirs in ∼
9.9–9.0, ∼
8.4–8.2, ∼
6.9–6.5 and ∼
4.5
ka
14C BP correlate well with palaeogeomorphic and palaeohydrological records from nearby Polish Carpathians. The study confirms that the LG/Holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas, but also in medium-high mountains of Central Europe.
Trimastigids are free-living, anaerobic protists that are closely related to the symbiotic oxymonads, forming together the taxon Preaxostyla (Excavata: Metamonada). We isolated fourteen new strains ...morphologically corresponding to two species assigned to Trimastix (until now the only genus of trimastigids), Trimastix marina and Trimastix pyriformis. Unexpectedly, marine strains of Trimastix marina branch separately from freshwater strains of this morphospecies in SSU rRNA gene trees, and instead form the sister group of all other Preaxostyla. This position is confirmed by three-gene phylogenies. Ultrastructural examination of a marine isolate of Trimastix marina demonstrates a combination of trimastigid-like features (e.g. preaxostyle-like I fibre) and ancestral characters (e.g. absence of thickened flagellar vane margins), consistent with inclusion of marine T. marina within Preaxostyla, but also supporting its distinctiveness from ‘freshwater T. marina’ and its deep-branching position within Preaxostyla. Since these results indicate paraphyly of Trimastix as currently understood, we transfer the other better-studied trimastigids to Paratrimastix n. gen. and Paratrimastigidae n. fam. The freshwater form previously identified as T. marina is described as Paratrimastix eleionoma n. sp., and Trimastix pyriformis becomes Paratrimastix pyriformis n. comb. Because of its phylogenetic position, ‘true’ Trimastix is potentially important for understanding the evolution of mitochondrion-related organelles in metamonads.
Landslides affecting narrow mountainous valleys might significantly determine sedimentation dynamics of floodplains. We present here a detailed study of the sedimentary archive within a ...landslide-controlled impounded floodplain (Smrdutá site, Czech Flysch Carpathians) using geochronological (14C and 137Cs), sedimentological and pollen evidence. A sedimentary sequence deposited above the landslide dam points to three highly discontinuous and instantaneous depositional events dated to 4.6 and 2.0 cal. ka BP, whereas the last cycle started approximately in the 17–18th centuries and has continued to recent times. Such sedimentary pulses characterized by the duration of several decades to a few centuries originated as a consequence of the blockage and/or reduction of the valley floor width by successive long-runout landslides from a slope formed by tectonically and lithologically anisotropic flysch bedrock. Stages of mass movement activity revealed by the Smrdutá landslide correlate well with major humid late-Holocene oscillations suggesting its high sensitivity to century-scale climatic deteriorations. The character of lithological units forming individual sedimentary pulses, erosional hiatuses and sedimentary traces caused by the July 1997 extreme flood indicate a decisive role of large flood events during accretion and erosion of the floodplain-impounded section.
Climatic factors are considered major causes and triggers of slope instability, but the palaeoclimatic implications of landslides have not yet been systematically reviewed. As inferred from ...landslides dated to the Late Glacial and Holocene, glacial-interglacial transitions are the major intervals of enhanced landsliding, but the length of this interval varies between distinct types of landscapes. Mass movements in non-glaciated temperate mountain ranges, arid and tropical regions, and coastal areas intensified soon after the onset of the Holocene alongside the warming and wetting of the climate, whereas large rock slides in areas within the limits of Pleistocene glaciations mostly show a millennial-scale time lag with respect to glacier withdrawal. Although the incidence of landslides was ubiquitous throughout the Holocene, the mid- to late-Holocene transition (~5–4 ka) was especially favourable for the origin of landslides across distinct types of landscapes, indicating a strengthened role of mass movements during the culmination phases of interglacial climate optima. In addition, growing evidence suggests that the enhanced activity of landslides occurred during warmer interstadial conditions, which is best demonstrated in the temporal coincidence of arid-zone landslides with Quaternary “pluvials”. Future progress in the understanding of the relationships between landslides and Quaternary climate changes should benefit from the i) extension of datasets of dated landslides, ii) geographical expansion of dating studies to regions with a lack of chronologically determined landslides (e.g., tropics), iii) improvement of landslide-dating strategies involving the incorporation of independent palaeoclimatic proxies and iv) wider incorporation of numerical modeling within landslide-dating studies.
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•7-gene phylogenetic analysis clearly resolves relationships within Archamoebae.•The endobiotic lifestyle appeared at least three times during the evolution of the group.•The ...bacterial nitrogen fixation system was present in the last common ancestor of Archamoebae (LCAA).•Mitochondrial derivatives of the LCAA contained a sulfate activation pathway.•Comparative ultrastructural analysis of Mastigamoebidae “A” and “B” clades is presented.
Archamoebae is an understudied group of anaerobic free-living or endobiotic protists that constitutes the major anaerobic lineage of the supergroup Amoebozoa. Hitherto, the phylogeny of Archamoebae was based solely on SSU rRNA and actin genes, which did not resolve relationships among the main lineages of the group. Because of this uncertainty, several different scenarios had been proposed for the phylogeny of the Archamoebae. In this study, we present the first multigene phylogenetic analysis that includes members of Pelomyxidae, and Rhizomastixidae. The analysis clearly shows that Mastigamoebidae, Pelomyxidae and Rhizomastixidae form a clade of mostly free-living, amoeboid flagellates, here called Pelobiontida. The predominantly endobiotic and aflagellated Entamoebidae represents a separate, deep-branching lineage, Entamoebida. Therefore, two unique evolutionary events, horizontal transfer of the nitrogen fixation system from bacteria and transfer of the sulfate activation pathway to mitochondrial derivatives, predate the radiation of recent lineages of Archamoebae. The endobiotic lifestyle has arisen at least three times independently during the evolution of the group. We also present new ultrastructural data that clarifies the primary divergence among the family Mastigamoebidae which had previously been inferred from phylogenetic analyses based on SSU rDNA.
Abstract
The small subunit ribosomal RNA (SSU rRNA) gene is a widely used molecular marker to study the diversity of life. Sequencing of SSU rRNA gene amplicons has become a standard approach for the ...investigation of the ecology and diversity of microbes. However, a well-curated database is necessary for correct classification of these data. While available for many groups of Bacteria and Archaea, such reference databases are absent for most eukaryotes. The primary goal of the EukRef project (eukref.org) is to close this gap and generate well-curated reference databases for major groups of eukaryotes, especially protists. Here we present a set of EukRef-curated databases for the excavate protists—a large assemblage that includes numerous taxa with divergent SSU rRNA gene sequences, which are prone to misclassification. We identified 6121 sequences, 625 of which were obtained from cultures, 3053 from cell isolations or enrichments and 2419 from environmental samples. We have corrected the classification for the majority of these curated sequences. The resulting publicly available databases will provide phylogenetically based standards for the improved identification of excavates in ecological and microbiome studies, as well as resources to classify new discoveries in excavate diversity.
Landslides are important geomorphic agents in various mountainous settings. We document here a case of river piracy from the upper part of the Malá Brodská Valley in the Vsetínské Mts., Czech ...Republic (Rača Unit of the flysch Magura Group of Nappes, flysch belt of the Outer Western Carpathians) controlled by mass movement processes. Based on the field geological, geomorphological and geophysical data, we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley. Apart from the landslide processes, the presence of the N-striking fault, accentuated by higher flow rates of the eastern channel as a result of its larger catchment area, were the most critical factors of the river piracy. As a consequence of the river piracy, intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred. Deposits of two landslide dams document recent minimum erosion rates to be 18.8mm.ky−1 in the western (captured) catchment, and 3.6mm.ky−1 in the eastern catchment respectively. The maximum age of the river piracy is estimated to be of the late Glacial and/or the early Holocene.
•Landslides caused river piracy in Flysch Belt of the Outer Western Carpathians.•The landslides forced lateral erosion and about 400 m long abandoned valley developed.•Retrograde erosion was intensified in the elbow of capture and in the captured stream.•Estimated minimum erosion rates are 5.22 times higher in the captured catchment.
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