Testate amoebae colonizing a newly exposed land surface are of airborne origin

We hypothesized that at the very beginning of terrestrial ecosystem development, airborne testate amoebae play a pivotal role in facilitating organismic colonization and related soil processes. We, therefore, analyzed size and quantity of airborne testate amoebae and immigration and colonization success of airborne testate amoebae on a new land surface (experimental site “Chicken Creek”, artificial post-mining water catchment). Within an altogether 91-day exposure of 70 adhesive traps, 12 species of testate amoebae were identified to be of airborne origin. Phryganella acropodia (51% of all individuals found, diameter about 35–45 μm) and Centropyxis sphagnicola (23% of all individuals found, longest axis about 55–68 μm), occurred most frequently in the adhesive traps. We extrapolated an aerial amoeba deposition of 61 individuals d⁻¹ m⁻² (living and dead individuals combined). Although it would be necessary to have a longer sequence (some additional years), our analysis of the “target substrate” of aerial immigration (catchment site) may point to a shift from a stochastic (variable) beginning of community assembly to a more deterministic (stable) course. This shift was assigned to an age of seven years of initial soil development. Although experienced specialists are necessary to conduct these time-consuming studies, the presented data suggest that terrestrial amoebae are suitable indicators for initial ecosystem development and utilization.     

Palaeoecology of testate amoebae in a tropical peatland

We present the first detailed analysis of subfossil testate amoebae from a tropical peatland. Testate amoebae were analysed in a 4-m peat core from western Amazonia (Peru) and a transfer function developed from the site was applied to reconstruct changes in water table over the past ca. 8,000 years. Testate amoebae were in very low abundance in the core, especially in the lower 125 cm, due to a combination of poor preservation and obscuration by other organic matter. A modified preparation method enabled at least 50 testate amoebae to be counted in each core sample. The most abundant taxa preserved include Centropyxis aculeata, Hyalosphenia subflava, Phryganella acropodia and Trigonopyxis arcula. Centropyxis aculeata, an unambiguous wet indicator, is variably present and indicates several phases of near-surface water table. Our work shows that even degraded, low-abundance assemblages of testate amoebae can provide useful information regarding the long-term ecohydrological developmental history of tropical peatlands.     

Environmental factors influencing soil testate amoebae in herbaceous and shrubby vegetation along an altitudinal gradient in subarctic tundra (Abisko,Sweden)

Shifts in community composition of soil protozoa in response to climate change may substantially influence microbial activity and thereby decomposition processes. However, effects of climate and vegetation on soil protozoa remain poorly understood. We studied the distribution of soil testate amoebae in herbaceous and shrubby vegetation along an altitudinal gradient (from below the treeline at 500 m to the mid-alpine region at 900 m a.s.l.) in subarctic tundra. To explain patterns in abundance, species diversity and assemblage composition of testate amoebae, a data set of microclimate and soil chemical characteristics was collected. Both elevation and vegetation influenced the assemblage composition of testate amoebae. The variation was regulated by interactive effects of summer soil moisture, winter soil temperature, soil pH and nitrate ion concentrations. Besides, soil moisture regulated non-linear patterns in species richness across the gradient. This is the first study showing the effects of winter soil temperatures on species composition of soil protozoa. The effects could be explained by specific adaptations of testate amoebae such as frost-resistant cysts allowing them to survive low winter temperatures. We conclude that the microclimate and soil chemical characteristics are the main drivers of changes in protozoan assemblage composition in response to elevation and vegetation.     

Plants and testate amoebae as environmental indicators in cupriferous peatlands,New Brunswick,Canada

Vegetation, testate amoebae, and metal concentrations in water and soil (mostly peat) were studied in two copper-rich treed swamps located north of Sackville, New Brunswick, Canada. One of the sites is partly disturbed, characterized by bare soil nearly devoid of vegetation cover except for isolated patches of the moss species, Pohlia nutans, around seepages and small streams. Copper concentrations in soil and water samples were high but varied among plots. Values in soil samples were as high as 16,000 μg/g in the open area, with 4550 μg/g being the mean. The highest value in groundwater was 1540 μg/l, with 292 μg/l being the mean. Twenty-seven testate amoebae species were identified from soil samples. The most abundant species were Cyclopyxis arcelloides and Centropyxis spp. Principal component analysis and detrended correspondence analysis showed that their abundance was especially high in the open area where copper concentrations were high, while species diversity of testate amoebae was low in the open area. This study suggests potential use of mosses and testate amoebae as bio-indicators and bio-monitoring tools for metals such as copper.     

Seasonal changes in Sphagnum peatland testate amoeba communities along a hydrological gradient

Testate amoebae are an abundant and functionally important group of protists in peatlands, but little is known about the seasonal patterns of their communities. We investigated the relationships between testate amoeba diversity and community structure and water table depth and light conditions (shading vs. insolation) in a Sphagnum peatland in Northern Poland (Linje mire) in spring and summer 2010. We monitored the water table at five sites across the peatland and collected Sphagnum samples in lawn and hummock micro-sites around each piezometer, in spring (3 May) and mid-summer (6 August) 2010. Water table differed significantly between micro-sites and seasons (Kruskal–Wallis test, p = 0.001). The community structure of testate amoebae differed significantly between spring and summer in both hummock and lawn micro-sites. We recorded a small, but significant drop in Shannon diversity, between spring and summer (1.76 vs. 1.72). Strongest correlations were found between testate amoeba communities and water table lowering and light conditions. The relative abundance of mixotrophic species Hyalosphenia papilio, Archerella flavum and of Euglypha ciliata was higher in the summer.     

Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

Soil microbial communities significantly contribute to global fluxes of nutrients and carbon. Their response to climate change, including winter warming, is expected to modify these processes through direct effects on microbial functions due to osmotic stress, and changing temperature regimes. Using four European peatlands reflecting different frequencies of frost events, we show that peatland testate amoeba communities diverge among sites with different winter climates, and that this is reflected through contrasting functions. We found that exposure to harder soil frost promoted species β-diversity (species turnover) thus shifting the community composition of testate amoebae. In particular, we found that harder soil frost, and lower water-soluble phenolic compounds, induced functional turnover through the decrease of large species (−68%, >80 μm) and the increase of small-bodied mixotrophic species (i.e. Archerella flavum; +79%). These results suggest that increased exposure to soil frost could be highly limiting for large species while smaller species are more resistant. Furthermore, we found that β-glucosidase enzymatic activity, in addition to soil temperature, strongly depended of the functional diversity of testate amoebae (R² = 0.95, ANOVA). Changing winter conditions can therefore strongly impact peatland decomposition process, though it remains unclear if these changes are carried-over to the growing season.     

Testate amoebae community pattern in different types of boundary structures at the water-land contact zone

The patterns of changes in the species richness, abundance, species composition, and species structure of the testate amoebae community along six different types of water-land boundaries in the Medveditsa River (Don river Basin) were studied, namely, a new boundary, terrigenous and reogeneous edges, reogeneous and terrigenous hemiecotones, and the full ecotone. The testate amoebae communities are divided into terrestrial and aquatic variants for all types of boundaries. Hydrophilic species of the genera Arcella, Diffugia, Cyphoderia, and Pseudodifflugia dominate in the aquatic types of communities while pedobiont and eurybiont groups from the genera Centropyxis, Euglypha, Plagiopyxis, and Trinema are characteristic of the terrestrial communities. A decrease in the abundance and species richness of testate amoebae in the boundary zones was detected.     

Diversity and community patterns of testate amoebae in Bau Sen and Bau Trang lakes in Binh Thuan Province,Vietnam

The species composition and distribution of testate amoebae in Bau Sen and Bau Trang lakes (Binh Thuan Province, Vietnam) were investigated. Fifty-three species, varieties and forms have been identified from the water column and sediments. Twenty-seven species, varieties and forms from the genera Arcella, Centropyxis, Cyclopyxis, Difflugia and Pyxidicula were found in Vietnam for the first time. The updated list of testate amoebae in Vietnam now includes 286 taxa. The genera Arcella, Centropyxis and Difflugia are characterized by the highest frequency of occurrence. The species diversity of Arcella, Centropyxis, Difflugia was the highest. Centropyxis aculeata, Arcella discoides, Difflugia schurmanni, Netzelia oviformis and Difflugia limnetica were the most common species. Many species have shown restricted distribution, some species have been found only in one lake and not been found in another lake. The number of observed species, varieties, and forms in each lake is 34. The average number of the species per sample on the shores of the lakes subjected to human agricultural activity was significantly higher than in the samples from the shores of the lakes with less anthropogenic disturbance. The curves of “cumulative species number vs. sampling effort” are well fitted by equations S = 7.60 N ^0.69 for Bau Sen lake and S = 12.52 N ^0.46 for Bau Trang. The curves are unsaturated, which indicates that more intensive investigations of testate amoebae should be expected to reveal more species.     

Structure and seasonal dynamics of the protozoan community (heterotrophic flagellates,ciliates, amoeboid protozoa) in the plankton of a large river (River Danube,Hungary)

Seasonal dynamics of all major protozoan groups were investigated in the plankton of the River Danube, upstream of Budapest (Hungary), by bi-weekly sampling over a 1-year long period. Sixty-one heterotrophic flagellate, 14 naked amoeba, 50 testate amoeba, 4 heliozoan and 83 ciliate morphospecies were identified. The estimated abundance ranges of major groups throughout the year were as follows: heterotrophic flagellates, 0.27–7.8×10⁶ ind. l^?1; naked amoebae, max. 3300 ind. l^?1; testaceans, max. 1600 ind. l^?1; heliozoans, max. 8500 ind. l^?1; ciliates, 132–34,000 ind. l^?1. In terms of biovolume, heterotrophic flagellates dominated throughout the year (max. 0.58 mm³ l^?1), and ciliates only exceeded their biovolume in summer (max. 0.76 mm³ l^?1). Naked amoeba and heliozoan biovolume was about one, and testacean biovolume 1–3, orders of magnitude lower than that of ciliates. In winter, flagellates, mainly chrysomonads, had the highest biomass, whilst ciliates were dominated by peritrichs. In 2005 from April to July a long spring/summer peak occurred for all protozoan groups. Beside chrysomonads typical flagellates were choanoflagellates, bicosoecids and abundant microflagellates (large chrysomonads and Collodictyon). Most abundant ciliates were oligotrichs, while Phascolodon, Urotricha, Vorticella, haptorids, Suctoria, Climacostomum and Stokesia also contributed significantly to biovolume during rapid succession processes. In October and November a second high protozoan peak occurred, with flagellate dominance, and slightly different taxonomic composition.     

Testate amoebae taxonomy and trait diversity are coupled along an openness and wetness gradient in pine-dominated Baltic bogs

Sphagnum peatlands host a high abundance of protists, especially testate amoebae. Here, we designed a study to investigate the functional diversity of testate amoebae in relation to wetness and forest cover in Baltic bogs. We provided new data on the influence of openness/wetness gradient on testate amoebae communities, showing significant differences in selected testate amoebae (TA) traits. Three key messages emerged from our investigations: 1) we recorded an effect of peatland surface openness on testate amoebae functional traits that led us to accept the hypothesis that TA traits differ according to light intensity and hydrology. Mixotrophic species were recorded in high relative abundance in open plots, whereas they were nearly absent in forested sites; 2) we revealed a hydrological threshold for the occurrence of mixotrophic testate amoebae that might be very important in terms of peatland functioning and carbon sink vs. source context; and 3) mixotrophic species with organic tests were nearly absent in forested sites that were dominated by heterotrophic species with agglutinated or idiosomic tests. An important message from this study is that taxonomy of TA rather indicates the hydrological gradient whereas traits of mixotrophs the openness gradient.     

Testate amoebae community structure in the moss biotopes of streams

The specific composition and community structure of testate amoebae in the moss biotopes of streams were studied in the Sura River basin (Middle Volga region). Twenty-nine species and forms were identified. The eurybiont species Trinema enchelys, Euglypha ciliata glabra, Centropyxis aerophila, Tracheleuglypha dentata, Crythion dubium, Centropyxis cassis, Trinema complanatum, and Trinema lineare are dominant. The species richness varies from 2 to 11 species per sample, the abundance is 100 to 4000 ind./g of absolutely dry moss. The degree of forest covering in the basin, hydrochemical peculiarities (the amount of biogenic elements and water hardness) of streams, the size of streams, and environmental contamination are possible factors that determine the specific character of the composition and structure of testate amoebae communities.     

Comparative ecology of vascular plant,bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland

Monitoring tools are needed to assess changes in peatland biotic communities and ecosystem functions in response to on-going climate and other environmental changes. Although the responses of soil organisms and plants to ecological gradients and perturbations do not always correlate, peatland monitoring is mainly based on vegetation surveys. Testate amoebae, a group of protists, are important contributors to carbon and nitrogen cycling in organic soils and are useful bioindicators in peatland ecology and paleoecology. There is however little comparative data on the value of testate amoebae, vascular plants and bryophytes as bioindicators of micro-environmental gradients in peatlands.We compared the relationships of testate amoebae, bryophytes, and vascular plants with soil temperature, water table depth, micro-habitats and the carbon and nitrogen content of Sphagnum mosses in four peatlands along a 1300 m altitudinal gradient in Switzerland. We used the full diversity of vascular plants and bryophyte but only a selection of ten easily identifiable testate amoeba morpho-taxa (i.e. species or species-complexes).Indirect and direct gradient ordinations, multiple factor analysis (MFA) and transfer function models for inferring water table depth showed that a selection of ten testate amoeba taxa are more powerful (% variance explained in RDA) and accurate (discrimination among habitats) indicators of local conditions (micro-habitat type, water table depth and Sphagnum C/N ratio) than the vegetation (vascular plants and bryophytes either individually or combined and considering the full diversity).Our study showed that a limited list of ten easily identifiable testate amoeba taxa have higher bioindication value than the full bryophytes and vascular plants. Furthermore, testate amoebae can be analyzed on samples collected at any season (accessibility allowing and if precise sampling sites are well marked) – a clear advantage for biomonitoring and can be used to infer past changes from the peat record at the same taxonomic resolution. This simple approach could therefore be very useful for biomonitoring of peatlands.     

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.     

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental field climate manipulations. All manipulations were accomplished using open top chambers in a dry blanket bog located in the sub-Arctic (Abisko, Sweden). We estimated sensitivity of abundance, diversity and assemblage structure of living and empty shell assemblages of testate amoebae in the living and decaying layers of Sphagnum. Our results show that, in a sub-arctic climate, testate amoebae are more sensitive to climate changes in the growing season than in winter. Summer warming reduced species richness and shifted assemblage composition towards predominance of xerophilous species for the living and empty shell assemblages in both layers. The higher soil temperatures during the growing season also decreased abundance of empty shells in both layers hinting at a possible increase in their decomposition rates. Thus, although possible effects of climate changes on preservation of empty shells should always be taken into account, species diversity and structure of testate amoeba assemblages in dry subarctic bogs are sensitive proxies for climatic changes during the growing season.     

Flourish or Flush: Effects of Simulated Extreme Rainfall Events on Sphagnum-dwelling Testate Amoebae in a Subarctic Bog (Abisko, Sweden)

Extreme precipitation events are recognised as important drivers of ecosystem responses to climate change and can considerably affect high-latitude ombrotrophic bogs. Therefore, understanding the relationships between increased rainfall and the biotic components of these ecosystems is necessary for an estimation of climate change impacts. We studied overall effects of increased magnitude, intensity and frequency of rainfall on assemblages of Sphagnum-dwelling testate amoebae in a field climate manipulation experiment located in a relatively dry subarctic bog (Abisko, Sweden). The effects of the treatment were estimated using abundance, species diversity and structure of living and empty shell assemblages of testate amoebae in living and decaying layers of Sphagnum. Our results show that increased rainfall reduced the mean abundance and species richness of living testate amoebae. Besides, the treatment affected species structure of both living and empty shell assemblages, reducing proportions of hydrophilous species. The effects are counterintuitive as increased precipitation-related substrate moisture was expected to have opposite effects on testate amoeba assemblages in relatively dry biotopes. Therefore, we conclude that other rainfall-related factors such as increased infiltration rates and frequency of environmental disturbances can also affect testate amoeba assemblages in Sphagnum and that hydrophilous species are particularly sensitive to variation in these environmental variables.     

Nested PCR assay for the rapid detection of Naegleria fowleri from swimming pools in Egypt

The free-living amoeboflagellate Naegleria fowleri is the only species infects humans world widely distributed. N. fowleri is the causative agent of very rare but severe brain infection called primary amoebic meningo-encephalitis (PAM), a rapidly fatal disease of the central nervous system mainly in immuno-compromised individuals. N. fowleri infects human through the entry of the nose, and it happens when human swimming or diving in warm freshwater, such as lakes, rivers and swimming pools. The disease is acute, and patients often die within 5–10 days and before the infectious agent can be diagnosed. Limited information is available about the existence of pathogenic N. fowleri, in Egypt, so the present of N. fowleri is an important public health. In the present study, we examined hundred water, dust and swap samples collected from 5 swimming pools in Cairo, Egypt. Based on morphological characteristics of trophozoite and cyst, flagellation test 56% of thermo-tolerant Naegleria like amoeba was detected. The incidence of thermo-tolerant free-living amoebae reached 84, 80and 70% from water, cotton swap and dust samples, respectively at cultivation temperature of 45 °C. The highest occurrence of thermo-tolerant amoebae were recorded in summer (100 & 87.5%) while the lowest one were recorded in winter (58 & 37.5%) in both water and dust samples, respectively. In swap samples, the highest occurrence of thermo-tolerant free-living amoeba was recorded in both summer and spring (100%), while the lowest one was recorded in winter (40%). N. fowleri was performed on 24 samples from a total of 56 (42.2%) samples which are positive by culture. Nested PCR using Mp2Cl5 gene primers that is unique to N. fowleri was carried out. The N. fowleri specific primer showed band at 166 bp against 24 of 56 (42.2%) samples. The majority of positive samples unique to N. fowleri was detected in water samples followed by swap samples and finally dust samples 14 of 24 (58%), 7 of 24 (29%), 3 of 24 (13%), respectively. In conclusion, swimming pools water may be the source of Naegleria invasion. The use of molecular methods to identify free-living amoebae N. fowleri could provide a more rapid means to diagnose infections caused by those amoebae.     

Diverse fossil amoebae in German Mesozoic amber

Fossil amoebae are very rare, although their evolutionary history extends back into the Proterozoic. The Cenomanian amber of Schliersee (southern Germany) is very rich in micro-organisms and contains the highest diversity of fossil freshwater rhizopods (Gymnamoebia and Testacealobosia) yet discovered. Altogether seven testate amoebae and one gymnamoebian species are recorded from this Mesozoic amber. The four newly discovered taxa described in this paper can be assigned to the extant species Centropyxis delicatula , Centropyxis hirsuta , Phryganella acropodia and Phryganella paradoxa . Over 200 individuals of Phryganella paradoxa are preserved. Together with their syninclusions, the amoebae are species of limnetic or limnetic–terrestrial microcoenoses. The presence of 100-myr-old fossils with extant representatives suggests evolutionary stasis of these freshwater amoebae. However, not all modern testacean families have been recorded from Mesozoic limnetic habitats. Our experimental studies verify that naked and testate amoebae can be embedded in resins.     

Diversity of fungal endophytes in shrubby medicinal plants of Malnad region,Western Ghats,Southern India

A total of 6125 fungal endophytes were isolated from 9000 leaf segments of 15 medicinal shrubs growing in Malnad region of Western Ghats, Southern India, during winter, monsoon, and summer seasons. These fungal isolates belonged to Ascomycota (8.6 %), Coelomycetes (26.0 %), Hyphomycetes (28.0 %), Mucoromycotina (0.3 %) and sterile forms (4.9 %). Alternaria, Chaetomium, Fusarium, Colletotrichum, Cladosporium, Penicillium, Phyllosticta and Xylaria were the most frequently isolated. Significantly more isolates were obtained during the winter season than monsoon and summer seasons.     

The tempo-spatial variations of phytoplankton diversities and their correlation with trophic state levels in a large eutrophic Chinese lake

Lake Chaohu is one of the most eutrophic lakes in China. Research on this lake's seasonal and spatial variations in phytoplankton diversity is needed to understand the distribution of eutrophication, as well as to find appropriate comprehensive biodiversity indices to assess the eutrophication status of the lake. The present study indicated that the Margalef index of all samples was as low as 0.799 ± 0.543 in summer (August 2011) and as high as 1.467 ± 0.653 in winter (February 2012). The Margalef index of the river samples had a high mean value and substantial variation compared with the lake samples. The Peilou index of the lake samples was higher than that of the river samples in summer and autumn (November 2011) but lower than that of the river samples in winter. In spring (May 2012), the Peilou index of the western samples was lower than that of the eastern samples. The spatial distribution of the Shannon–Wiener index was more similar to that of the Peilou index in autumn and winter, while in spring and summer, the spatial distribution was affected by both species richness and evenness. High eutrophication levels occurred in the western lake in spring and summer, whereas high levels occurred in the eastern lake, especially in the middle of the lake, in autumn and winter. The total trophic state index (TSI) in all samples exhibited a significant negative correlation with the Margalef (r = −0.726) and Peilou (r = −0.530) indices but a significant positive correlation with the Shannon–Wiener (r = 0.654) index. The partial correlation analysis results implied that these phytoplankton biodiversity indices could serve as synthetic ecological indicators to assess the eutrophication condition of Lake Chaohu.     

Fluctuations of Testate Amoebae Populations (Rhizopoda) in Plankton from Different Environments on the Upper Paraná River Floodplain,Brazil

Fluctuations in temporal and spatial abundance are remarkable features of all animal populations. Regional synchrony of local population dynamics has been verified in several studies. This study investigated the existence of coherent patterns in temporal fluctuations of the principal testate amoebae population abundance in plankton from the upper Paraná river floodplain in Brazil. Testate amoebae sampling was carried out every three months, from February 2000 to November 2002, and twice in 2003. Sampling occurred in 12 environments associated with three different rivers. Samples were obtained at the subsurface of the pelagic region, using a motorized pump and a 68 μm mesh plankton net. Ninety–three testate amoebae species from eight families were identified. The families Difflugiidae, Arcellidae, and Centropyxidae had the greatest number of species. Arcella conica, A. discoides, A. vulgaris, Centropyxis aculeata, C. ecornis, Difflugia gramen, D. pseudogramen and Cucurbitella dentata were the most abundant species, and they were chosen for spatial synchrony analysis. No coherent pattern of abundance fluctuation was found, in any of the floodplain environments studied. Nevertheless, when analyzing only the channels, spatial synchrony was observed to Centropyxis ecornis. Mantel tests showed that the synchrony level, as identified by Spearman and Pearson correlations, was not correlated to geographic distance between environments. We conclude that regional factors in the Upper Paraná River floodplain are not the main determinants of the population dynamics of testate amoebae. The high floodplain heterogeneity seems determine a great relevance of local factors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)