Euglypha Rotunda Research Articles

Testate amoebae from the wetlands of the Phobjikha Valley of Bhutan, the Eastern Himalayas

The Kingdom of Bhutan in the Eastern Himalayas harbors a rich biodiversity. However, its detailed documentation still needs to be created, including not only macroorganisms but also protists. In the present study, as many as 105 taxa of testate amoebae were identified and directly counted in soil suspension samples collected from the wetlands of the Gangtey-Phobji Valley (generally Phobjikha), Wangdue Phodrang district. The most dominant were cosmopolitan species, e.g., Euglypha rotunda, Trinema lineare, T. complanatum, T. enchelys, Phryganella acropodia, and Plagiopyxis declivis. However, some taxa such as Centropyxis deflandriana, C. stenodeflandriana, Hoogenraadia cf. humicola, Pareuglypha reticulata, and Sphenoderia chardezi have a geographically restricted distribution and/or are considered rare. Some specimens could not be assigned to already described species (Centropyxis dentata sp. nov. and Difflugia fusiforma sp. nov.) or were highly similar to known species but differed in size or other taxonomically important characteristics (e.g., Hoogenraadia cf. humicola and Planhoogenraadia sp.). To our knowledge, this study is the first to present a comprehensive list of testate amoebae from Bhutan, including some new and rare species. The discovery of a remarkable diversity of testate amoebae in only a few soil samples suggests that this remote and largely unexplored region likely harbors many more intriguing species.

Distribution of testate amoebae in bryophyte communities in São Miguel Island (Azores Archipelago).

BackgroundTestate amoebae are a polyphyletic group of protists living preferentially in soils, freshwaters and wetlands. These Protozoa have a worldwide distribution, but their presence and diversity in the Azores (a remote oceanic archipelago) is poorly known, with only twelve taxa recorded so far. The published information reflects occasional collections from sporadic field visits from naturalists to São Miguel Island, mainly in the nineteenth century. To overcome this limitation, a standardised survey was carried out on the Island, sampling different types of habitats from several localities to provide the distribution and information on species ecology of testate amoebae.New informationIn this study, 43 species of testate amoebae were recorded (within a total of 499 occurrences), belonging to two orders of Protista (26 Arcellinida and 17 Euglyphida). The most frequently occurring testate amoebae were Euglypha strigosa, Trinema lineare, Euglypha rotunda, Assulina muscorum and Cyclopyxis eurystoma. The most diverse genus was Euglypha (six species). A total of 38 species are new records for the Azores Archipelago. These data help to improve knowledge of the geographical distribution of testate amoebae in the northern hemisphere and their diversity in the Azores Archipelago.

Tolerance of testate amoeba species to rising sea levels under laboratory conditions and in the South Pacific

Testate amoebae are ubiquitous unicellular eukaryotic micro-organisms. They occur in high abundances in terrestrial habitats and contribute to important ecological and biogeochemical processes like silicon cycling. Little is known about the growth of testate amoeba populations under hyperosmotic stress, as caused by salinity pulses due to coastal flooding. Given the increasing sea-levels in response to climate change we address this knowledge gap by jointly considering results from a laboratory experiment and a field study in Tuvalu (South Pacific). In the laboratory experiment, Trinema galeata cultures tolerated up to 1 g NaCl L−1 but showed a pronounced decrease in growth rate probably due to interactions with other micro-organisms. Tracheleuglypha dentata cultures had the highest growth rate at 0.5 g NaCl L−1. At higher salt concentrations (5–10 g NaCl L−1), a strongly reduced growth and rapid closing of the shell aperture with a plug occurred, which can be considered as rapid pre-encystment. Euglypha rotunda cultures had the highest growth rates at 1 g NaCl L−1. At higher salt concentrations (5–10 g NaCl L−1), a strongly reduced growth and spherical shrinking of cell plasma occurred, which is again considered as rapid pre-encystment. After seven weeks of exposure, a replacement of the 5 and 10 g NaCl L−1 culture medium by NaCl-free medium resulted in a quick recovery of T. dentata and E. rotunda cultures, but not of T. galeata cultures. Generally, cultures of T. dentata showed the highest growth rates and shortest generation times (up to 0.37/1.91 day−1, respectively). In the field study, different flooding regimes resulted in fundamental changes of the composition of soil amoeba communities. In conclusion, terrestrial testate amoebae can tolerate at least short periods of exposure to moderate salinity caused by flooding stress due to their ability to form cysts and fast growth rates.

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

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.

Testate amoebae analysis in the peat deposits of the swamp Dolgon’koye in the south of Western Siberia and peatland paleohydrology for last 3100 years

Our research is devoted to paleohydrological reconstruction in the swamp located in the river valley on the piedmont of the Altai Mountains in the south of Western Siberia. The reconstruction was carried out based on rhizopod analysis for the last 3100 cal yr. A large amount of different testate amoebae was found in the peat. Total 64 testate amoebae taxa were recorded in the peat core with the most abundant being: Trinema lineare, Centropyxis aculeata, C. aerophila, Euglypha rotunda, Cryptodifflugia sp. Decrease of surface wetness in the swamp are observed 2280, 2140, 1900–600 cal yr BP and increase – in 2700, 2500–1900, 230–215 cal yr BP. The results of our reconstruction of the swamp paleohydrology agrees well with the paleoclimatic data obtained earlier for the central area of the south of Western Siberia Plain. It indicates a high sensitivity of the swamp to climatic changes in the Holocene. The rhizopod analysis proved to be very effective when used for paleohydrology reconstruction in minerotrophic peat.

Culture growth of testate amoebae under different silicon concentrations

Testate amoebae with self-secreted siliceous shell platelets (“idiosomes”) play an important role in terrestrial silicon (Si) cycles. In this context, Si-dependent culture growth dynamics of idiosomic testate amoebae are of interest. Clonal cultures of idiosomic testate amoebae were analyzed under three different Si concentrations: low (50μmolL−1), moderate/site-specific (150μmolL−1) and high Si supply (500μmolL−1). Food (Saccharomyces cerevisiae) was provided in surplus. (i) Shell size of four different clones of idiosomic testate amoebae either decreased (Trinema galeata, Euglypha filifera cf.), increased (E. rotunda cf.), or did not change (E. rotunda) under the lowest Si concentration (50μmolSiL−1). (ii) Culture growth of idiosomic Euglypha rotunda was dependent on Si concentration. The more Si available in the culture medium, the earlier the entry into exponential growth phase. (iii) Culture growth of idiosomic Euglypha rotunda was dependent on origin of inoculum. Amoebae previously cultured under a moderate Si concentration revealed highest sustainability in consecutive cultures. Amoebae derived from cultures with high Si concentrations showed rapid culture growth which finished early in consecutive cultures. (iv) Si (diluted in the culture medium) was absorbed by amoebae and fixed in the amoeba shells resulting in decreased Si concentrations.

Long-term hydrological dynamics and fire history over the last 2000 years in CE Europe reconstructed from a high-resolution peat archive

Sphagnum peatlands in the oceanic-continental transition zone of Poland are currently influenced by climatic and anthropogenic factors that lead to peat desiccation and susceptibility to fire. Little is known about the response of Sphagnum peatland testate amoebae (TA) to the combined effects of drought and fire. To understand the relationships between hydrology and fire dynamics, we used high-resolution multi-proxy palaeoecological data to reconstruct 2000 years of mire history in northern Poland. We employed a new approach for Polish peatlands – joint TA-based water table depth and charcoal-inferred fire activity reconstructions. In addition, the response of most abundant TA hydrological indicators to charcoal-inferred fire activity was assessed. The results show four hydrological stages of peatland development: moderately wet (from ∼35 BC to 800 AD), wet (from ∼800 to 1390 AD), dry (from ∼1390 to 1700 AD) and with an instable water table (from ∼1700 to 2012 AD). Fire activity has increased in the last millennium after constant human presence in the mire surroundings. Higher fire activity caused a rise in the water table, but later an abrupt drought appeared at the onset of the Little Ice Age. This dry phase is characterized by high ash contents and high charcoal-inferred fire activity. Fires preceded hydrological change and the response of TA to fire was indirect. Peatland drying and hydrological instability was connected with TA community changes from wet (dominance of Archerella flavum, Hyalosphenia papilio, Amphitrema wrightianum) to dry (dominance of Cryptodifflugia oviformis, Euglypha rotunda); however, no clear fire indicator species was found. Anthropogenic activities can increase peat fires and cause substantial hydrology changes. Our data suggest that increased human fire activity was one of the main factors that influenced peatland hydrology, though the mire response through hydrological changes towards drier conditions was delayed in relation to the surrounding vegetation changes.

Ecology of testate amoebae and their potential use as palaeohydrologic indicators from peatland in Sanjiang Plain, Northeast China

Testate amoebae are sensitive indicators of substrate moisture in peatlands. Over the last decades, they have been studied to reconstruct hydrological changes since the Holocene. However, these studies have been geographically restricted to North America and Europe. We conducted the first investigation of testate amoebae on the largest continental fresh water wetland in the Sanjiang Plain, China. The objectives of this study were to provide baseline data on the ecology of testate amoebae in the peatlands of Northeast China and to assess the potential of using them as environmental indicators in this ecosystem. We examined modern testate amoeba assemblages and species-environmental relationships at 46 microsites within 5 waterlogged depressions. The environmental parameters measured included: depth to water table, pH, and loss on ignition. The results showed that the dominant species were Trinema complanatum type, Euglypha rotunda type, Euglypha strigosa type, and Centropyxis cassis type. Redundancy analysis demonstrates that water table depth has the most important effect on testate amoeba assemblages, explaining 16.7% (p = 0.002) of the total variance. pH was not a statistically significant factor for testate amoeba assemblages. Weighted averaging and weighted averaging partial least squares models were used to build transfer functions for depth to water table. The best performing transfer function was generated by the weighted averaging partial least squares model with an r 2 LOSO of 0.62 and RMSEPLOSO of 6.96 cm. Results indicate that testate amoebae in waterlogged depression peatland have the potential to be used as indicators for hydrological changes and for palaeohydrologic reconstructions in the Sanjiang Plain.

Ecology of Testate Amoebae in an Amazonian Peatland and Development of a Transfer Function for Palaeohydrological Reconstruction

Tropical peatlands represent globally important carbon sinks with a unique biodiversity and are currently threatened by climate change and human activities. It is now imperative that proxy methods are developed to understand the ecohydrological dynamics of these systems and for testing peatland development models. Testate amoebae have been used as environmental indicators in ecological and palaeoecological studies of peatlands, primarily in ombrotrophic Sphagnum-dominated peatlands in the mid- and high-latitudes. We present the first ecological analysis of testate amoebae in a tropical peatland, a nutrient-poor domed bog in western (Peruvian) Amazonia. Litter samples were collected from different hydrological microforms (hummock to pool) along a transect from the edge to the interior of the peatland. We recorded 47 taxa from 21 genera. The most common taxa are Cryptodifflugia oviformis, Euglypha rotunda type, Phryganella acropodia, Pseudodifflugia fulva type and Trinema lineare. One species found only in the southern hemisphere, Argynnia spicata, is present. Arcella spp., Centropyxis aculeata and Lesqueresia spiralis are indicators of pools containing standing water. Canonical correspondence analysis and non-metric multidimensional scaling illustrate that water table depth is a significant control on the distribution of testate amoebae, similar to the results from mid- and high-latitude peatlands. A transfer function model for water table based on weighted averaging partial least-squares (WAPLS) regression is presented and performs well under cross-validation (r(2)(apparent)= 0.76, RMSE = 4.29; r(2)(jack)= 0.68, RMSEP =5.18). The transfer function was applied to a 1-m peat core, and sample-specific reconstruction errors were generated using bootstrapping. The reconstruction generally suggests near-surface water tables over the last 3,000 years, with a shift to drier conditions at c. cal. 1218-1273 AD.

Distribution of soil-inhabiting testate amoebae along a mountain slope (Baikal Lake region, Khamar-Daban ridge, Cherskii peak)

The specific composition and distribution of soil-inhabiting testate amoebae along the Cherskii peak slope (Khamar-Daban mountain ridge, Lake Baikal region) were studied within the altitude range from 1000 to 1570 m above sea level according to the changes in biogeocenoses from birch-aspen to cedar-fir forests to cedar-fir-bush forest-tundra. One-hundred-four taxa were identified. The most common species are ubiquits with a wide geographical distribution: Trinema lineare, Euglypha levis, Euglypha rotunda, Trinema enchelys, Phryganella acropodia, Tracheleuglypha dentata, Assulina muscorum, Trinema complanatum, and Centropyxis aerophila. The species richness varies from 12 to 40 species per sample, and the abundance varies from 500 to 120000 ind. per gram of absolutely dry soil. The spatial heterogeneity of the specific composition grows with altitude, and the community composition changes. The absence of a common pattern in the cenotic changes in the communities of testate amoebae in Western Europe and the Lake Baikal region is discussed.

Houses made by protists

Houses made by protists

Moss-dwelling testate amoebae and their community in Dajiuhu peatland of Shennongjia Mountains, China

Testate amoebae from a large fen peatland of China were investigated in August 2009. Thirty-six testate amoebae species belonging to 16 genera and one rotifer were identified. Three relatively drier indicator species, Assulina muscorum, Assulina seminulum, and Trinema-corythion type, were the dominate species, comprising 54% of total amoebae shells. Non-metric multidimensional scaling (NMS) ordination divided the testate amoebae assemblages into two groups – a drier group including A. muscorum, A. seminulum, Euglypha rotunda type, Trinema-corythion type, and Plagiopyxis callida and a wetter group including Centropysis cassis, Cyphoderia ampulla, Difflugia oblonga, Difflugia lanceolata, Euglypha strigosa type, Nebela galeata, Nebela lageniformis, and Quadruella symmetrica. Pearson correlations showed that most testate amoebae species between the two groups are negatively correlated, reflecting the possible influence of a moisture gradient. However, the ubiquitous distributions of other testate amoebae in the two-dimensional NMS ordination map suggested that factors other than moisture are also influencing the testate amoebae community in the fen.

The Impact of Simulated Sulfate Deposition on Peatland Testate Amoebae

Peatlands subjected to sulfate deposition have been shown to produce less methane, believed to be due to competitive exclusion of methanogenic archaea by sulfate-reducing bacteria. Here, we address whether sulfate deposition produces impacts on a higher microbial group, the testate amoebae. Sodium sulfate was applied to experimental plots on a Scottish peatland and samples extracted after a period of more than 10 years. Impacts on testate amoebae were tested using redundancy analysis and Mann-Whitney tests. Results showed statistically significant impacts on amoebae communities particularly noted by decreased abundance of Trinema lineare, Corythion dubium, and Euglypha rotunda. As the species most reduced in abundance are all small bacterivores we suggest that our results support the hypothesis of a shift in dominant prokaryotes, although other explanations are possible. Our results demonstrate the sensitivity of peatland microbial communities to sulfate deposition and suggest sulfate may be a potentially important secondary control on testate amoebae communities.

Community Assembly of Terrestrial Testate Amoebae: How is the Very First Beginning Characterized?

Testate amoebae play an important role at the very first beginning of succession on land. We used litterbags buried into four different soils to study the early colonization (which occurred within less than 55 days) and establishment of testate amoebae. The litterbag cellulose exposed at the youngest mining site poor in nitrogen and phosphorus was colonized firstly in high abundances, whereas the substrate introduced into the reference sites of undisturbed soil was colonized slowly and in low densities. Besides the (expected) small-sized r-strategists (e.g., Euglypha rotunda, Tracheleuglypha dentata, and Trinema lineare), large-sized K-strategists (e.g., Centropyxis spp., Phryganella acropodia) occurred in remarkably high densities on all sites. Species that colonized the cellulose in high densities (e.g., P. acropodia and T. dentata) were found extremely rarely in the adjacent source substrate and vice versa, stressing the importance of the target substrate quality. In the course of the experiment, the influencing environmental factors became more complex, as shown by redundancy analysis (RDA). Concerning the amoebal community, there was a change from variability to stability, as visualized by cluster analysis. Adjacent litterbags within an investigation site revealed amoebal species and abundances with an increasing similarity during exposition time, whereas the litterbags between the four investigation sites were colonized differently. These observations point to a stochastic (variable) beginning of community assembly, changing to a more deterministic (stable) course. No species replacement has been observed, which is an essential part of most successional theories. Thus, the more flexible concept of "community assembly" should be considered instead of "succession" for protozoa. The stochastic beginning of community assembly and the lack of species replacement are explained by a neutral community model.

DISTRIBUTION OF THECAMOEBIANS (TESTATE AMOEBAE) IN SMALL LAKES AND PONDS, BARBADOS, WEST INDIES

Thecamoebian faunas identified from 15 small permanent and ephemeral lakes and ponds on Barbados, West Indies, are characterized by low numbers of individuals and low species diversities (Shannon-Wiener Diversity Index = 0–1.4). Four lakes and ponds were found to contain no thecamoebians. The faunas were dominated by Centropyxis aculeata , with lesser numbers of Arcella vulgaris , Cucurbitella tricuspis , Centropyxis constricta and Cyclopyxis kahli . Very low numbers of the small idiosomic species Euglypha rotunda and an undifferentiated Corythion-Trinema type were also reported; the first records from a tropical region. Centropyxid-dominated faunas have been reported from other tropical areas and may indicate stressed environmental conditions. Additional important ecological controls on these faunas include substrate characteristics, the nature of bankside and aquatic vegetation and water depth. Land use characteristics do not appear to have a significant influence on faunal distribution, although the soil indicator thecamoebian species C. kahli seems to have been introduced into at least one pond through erosion from adjacent fields. Significant numbers of the salt marsh foraminiferid Jadammina macrescens , and lesser numbers of Polysaccammina ipohalina and Miliammina fusca , were found in one coastal pond, with a few specimens of J. macrescens found in another. The presence of this unusual, nonmarine foraminiferal fauna may relate to the intrusion of salt water into local ground waters, or possibly the introduction of sea salt from the prevailing Atlantic winds. Foraminiferal and thecamoebian colonization into the ponds may have been avian mediated.

Biological activity of soils from reclaimed open-cast coal mining areas in Upper Lusatia using testate amoebae (protists) as indicators

Immigration and colonisation of reclaimed open-cast coal mining areas in Lusatia (Eastern Germany, mainly the Görlitz region) by soil testate amoebae (protists) was investigated during the period 1996–1998. Colonisation took place within a few months depending on substrate quality and exposure (humus- and organism-free Pleistocene substrate or minicontainers filled with sterile, oven-dried poplar litter). Abundances and biomasses in two up to 46-year-old afforested mine soils were in the same order (or even higher) as in undisturbed forest soils, but typical humus-inhabiting, large-sized testate amoebae were lacking or occurred only rarely. Six ubiquists out of 48 taxa found contributed 61–87% to the overall abundance ( Centropyxis sphagnicola, Corythion dubium, Euglypha rotunda, Phryganella acropodia, Trinema complanatum, T. lineare). Generally, all test sites revealed a distinct testacean community, whose structure depended on age, substrate and stocking.

Directionally evolving genetic code: the UGA codon from stop to tryptophan in mitochondria.

For the comprehensive analyses of deviant codes in protistan mitochondria (mt), we sequenced about a 1.1-kb region of a mitochondrial (mt) gene, the cytochrome c oxidase subunit I (coxI) in two chlorarachniophytes, the filose amoeba Euglypha rotunda, the cryptomonad Cryptomonas ovata, the prymnesiophyte (haptophyte) Diacronema vlkianum (Pavlovales), and the diatom Melosira ambigua. As a result of this analysis, we noticed that the UGA codon is assigned to tryptophan (Trp) instead of being a signal for translational termination in two chlorarachniophytes and in E. rotunda. The same type of deviant code was reported previously in animals, fungi, ciliates, kinetoplastids, Chondrus crispus (a red alga), Acanthamoeba castellanii (an amoeboid protozoon), and three of the four prymnesiophyte orders with the exception of the Pavlovales. A phylogenetic analysis based on the COXI sequences of 56 eukaryotes indicated that the organisms bearing the modified code, UGA for Trp, are not monophyletic. Based on these studies, we propose that the ancestral mitochondrion was bearing the universal genetic code and subsequently reassigned the codon to Trp independently, at least in the lineage of ciliates, kinetoplastids, rhodophytes, prymnesiophytes, and fungi. We also discuss how this codon was directionally captured by Trp tRNA.

Molecular evolutionary analyses of nuclear-encoded small subunit ribosomal RNA identify an independent rhizopod lineage containing the Euglyphina and the Chlorarachniophyta.

The Rhizopoda comprise a diverse assemblage of protists which depend on lobose or filose pseudopodia for locomotion. The biochemical and morphological diversity of rhizopods has led to an uncertain taxonomy. Ribosomal RNA sequence comparisons offer a measure of evolutionary relatedness that is independent of morphology and has been used to demonstrate a polyphyletic origin of the Lobosea. We sequenced complete small subunit ribosomal RNA coding regions from the filose amoebae, Euglypha rotunda and Paulinella chromatophora (Euglyphina) to position these taxa in the eukaryote phylogeny. The neighbor-joining analyses show that E. rotunda and P. chromatophora share a monophyletic origin and are not closely related to any lobose amoebae in our analyses. Instead, the Euglyphina form a robust sister group to the Chlorarachniophyta. These results provide further evidence for the polyphyly of the Rhizopoda and support the creation of a new amoeboid lineage which includes the Euglyphina and the chlorarachniophyte algae; taxa with tubular mitochondrial cristae and filose or reticulate pseudopodia.

On the Soil Testate Amoebae Fauna (Protozoa: Rhizopoda) of the Spitsbergen Islands (Svalbard)

Summary: Altogether 48 species, varieties and forms of testate amoebae were determined in soil, moss and lichen samples from two regions of Spitsbergen Island (Svalbard). The species Centropyxis cassis , C. ecornis var. deflandrei , C. orbicularis , Cochliopodium erinaceum , Corythion delamarei , C. dubium v. aerophila , Difflugiella horrida , D. oviformis , D. pusilla , Euglypha rotunda var. dorsalis , E. tuberculata var. subcylindrica , Nebela bohemica , N. dentistoma , N. parvula , Phryganella microps , Plagiopyxis declivis , Pyxidicula ornata , Trigonopyxis arcula and Trinema lineare var. minuscula are new records for the testate amoebae fauna of Svalbard. Including these new species, 126 testate amoebae species, varieties and forms are known on Svalbard. The abundance, number of species and number of empty shells were relatively low.

On the Habitat Specificity of the Testate Amoebae Assemblages from Devon Island (NWT, Canadian Arctic), with the Description of a New Species: Difflugia ovalisina

Summary A classification analysis of samples from different habitats demonstrates the importance of some ubiquistic and cosmopolitic taxa in high arctic environments. The number of habitat specific assemblages was found to be rather low: only 6 out of 18 recognized assemblages could be linked to a specific habitat. These assemblages are: for the soils, the Plagiopyxis callida assemblage; for the moss habitats, the Assulina muscorum — Corythion dubium , and the Euglypha rotunda assemblages; for the aquatic habitats, the Trinema lineare and the Paraquadrula irregularis — P. penardi assemblages. A new species, Difflugia ovalisina , is described.