RESUMO

Ancestral adaptations to tropical-like climates drive most multicellular biogeography and macroecology. Observational studies suggest that this niche conservatism could also be shaping unicellular biogeography and macroecology, although evidence is limited to Acidobacteria and testate amoebae. We tracked the phylogenetic signal of this niche conservatism in far related and functionally contrasted groups of common soil protists (Bacillariophyta, Cercomonadida, Ciliophora, Euglyphida and Kinetoplastida) along a humid but increasingly cold elevational gradient in Switzerland. Protist diversity decreased, and the size of the geographic ranges of taxa increased with elevation and associated decreasing temperature (climate), which is consistent with a macroecological pattern known as the Rapoport effect. Bacillariophyta exhibited phylogenetically overdispersed communities assembled by competitive exclusion of closely related taxa with shared (conserved) niches. By contrast, Cercomonadida, Ciliophora, Euglyphida and Kinetoplastida exhibited phylogenetically clustered communities assembled by habitat filtering, revealing the coexistence of closely related taxa with shared (conserved) adaptations to cope with the humid but temperate to cold climate of the study site. Phylobetadiversity revealed that soil protists exhibit a strong phylogenetic turnover among elevational sites, suggesting that most taxa have evolutionary constraints that prevent them from colonizing the colder and higher sites of the elevation gradient. Our results suggest that evolutionary constraints determine how soil protists colonize climates departing from warm and humid conditions. We posit that these evolutionary constraints are linked to an ancestral adaptation to tropical-like climates, which limits their survival in exceedingly cold sites. This niche conservatism possibly drives their biogeography and macroecology along latitudinal and altitudinal climatic gradients.

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The reports of testate amoebae species in Colombia are limited to a few studies in lentic and peat bog systems; however, the diversity in lotic systems has been poorly investigated. Zooplankton sampling was performed in lotic environments of the Piedemonte Llanero in Colombia. Ten individuals of the species Arcella gandalfi were identified to document the first record of A. gandalfi from the Piedemonte Llanero in Colombia, expanding its distribution from Brazil to Colombia. This finding corroborates the status of A. gandalfi as a flagship species from the South America continent.

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We aimed to investigate spatial and temporal scales, abundance, and factors that structure the communities of protozoans in a tropical urban stream. Methods: Samples of water for analysis of biological communities (testate amoebae, ciliates and bacteria) and limnological variables were taken in the Mandacaru stream located in the Conservation Unit of Parque do Cinquentenário, in the city of Maringá, Paraná State, Brazil, in two hydrological periods (dry and rainy). We calculated the Water Quality Index (WQI) composed by nine parameters of water quality (dissolved oxygen, thermotolerant coliforms, pH, BOD, water temperature, total nitrogen, total phosphorous, turbidity, and total solids), Trophic State Index (TSI) for phosphorous and we used a Redundancy Analysis (RDA) to verify the influence of environmental variables in the protozoan community. Results: The WQI showed that water quality was considered good in some points and considered bad in other points. The TSI for phosphorus classified the stream as mesotrophic in the majority of sampled sites points (mean between 53.09 and 58.35). We identified 19 taxa of testate amoebae, belonging to six families, being Difflugiidae, Centropyxidae, and Arcellidae those with more species and 71 infrageneric taxa of ciliates, distributed in 12 orders being Peniculida the most representative order, followed by Euplotida. According to RDA analysis, samples of the dry period were characterized by higher values of bacteria density and concentrations of chlorophyll-a, total phosphorous, and total nitrogen. Ciliates and testate amoebae presented higher abundance values in some of the months characterized by higher precipitation and in conditions of higher system productivity. Conclusion: we may conclude that the Mandacaru stream, although strongly influenced by anthropic action, still presents an acceptable water quality. Lastly, we emphasize that protists abundance was strongly influenced by system productivity. This was evidenced by elevated protozoan densities where there was higher primary and bacterial productivity. Thus, these organisms must be considered in studies that aim at the identification of organisms that may indicate anthropic impacts and environmental quality.(AU)

O objetivo foi investigar, em escalas espacial e temporal, a abundância das comunidades de protozoários bem como os fatores intervenientes na estruturação das mesmas em um córrego urbano. Métodos: Amostras de água para análise de comunidades biológicas (amebas testáceas, ciliados e bactérias) e para análise de variáveis limnológicas foram tomadas no córrego Mandacaru localizado na Unidade de Conservação do Parque do Cinquentenário, na cidade de Maringá, Paraná State, Brasil, em dois períodos hidrológicos (seco e chuvoso). Calculamos o Índice de Qualidade de Água (IQA), o Índice de Estado Trófico (ETI) para fósforo e utilizamos uma Análise de Redundância (RDA) para verificar a influência de variáveis ambientais na comunidade de protozoários. Resultados: O IQA mostrou que a qualidade da água foi considerada boa em alguns pontos e considerada ruim em outros pontos, e o ETI para o fósforo classificou o córrego como mesotrófico na maioria dos locais amostrados (média entre 53,09 e 58,35). Foram identificados 19 táxons de amebas testáceas, pertencentes a seis famílias, sendo Difflugiidae, Centropyxidae e Arcellidae as mais especiosas, e 71 táxons de ciliados, distribuídos em 12 ordens, sendo Peniculida a ordem mais representativa, seguida por Euplotida. De acordo com a análise RDA, amostras do período seco foram caracterizadas por maiores valores de densidade bacteriana e concentrações de clorofila-a, fósforo total e nitrogênio total. As amebas testáceas e os ciliados apresentaram valores de abundância maiores em alguns dos meses caracterizados por maior precipitação e em condições de maior produtividade do sistema. Podemos concluir que o córrego Mandacaru, embora fortemente influenciado pela ação antrópica, ainda apresenta uma qualidade de água aceitável. Por fim, enfatizamos que a abundância de protistas foi fortemente influenciada pela produtividade do sistema. Isto foi evidenciado pelas elevadas densidades de protozoários onde houve maior produtividade primária e bacteriana. Assim, esses protistas devem ser considerados em estudos que visem à identificação de organismos que possam indicar impactos antrópicos e qualidade ambiental.(AU)

Assuntos

RESUMO

Abstract We aimed to investigate spatial and temporal scales, abundance, and factors that structure the communities of protozoans in a tropical urban stream. Methods: Samples of water for analysis of biological communities (testate amoebae, ciliates and bacteria) and limnological variables were taken in the Mandacaru stream located in the Conservation Unit of Parque do Cinquentenário, in the city of Maringá, Paraná State, Brazil, in two hydrological periods (dry and rainy). We calculated the Water Quality Index (WQI) composed by nine parameters of water quality (dissolved oxygen, thermotolerant coliforms, pH, BOD, water temperature, total nitrogen, total phosphorous, turbidity, and total solids), Trophic State Index (TSI) for phosphorous and we used a Redundancy Analysis (RDA) to verify the influence of environmental variables in the protozoan community. Results: The WQI showed that water quality was considered good in some points and considered bad in other points. The TSI for phosphorus classified the stream as mesotrophic in the majority of sampled sites points (mean between 53.09 and 58.35). We identified 19 taxa of testate amoebae, belonging to six families, being Difflugiidae, Centropyxidae, and Arcellidae those with more species and 71 infrageneric taxa of ciliates, distributed in 12 orders being Peniculida the most representative order, followed by Euplotida. According to RDA analysis, samples of the dry period were characterized by higher values of bacteria density and concentrations of chlorophyll-a, total phosphorous, and total nitrogen. Ciliates and testate amoebae presented higher abundance values in some of the months characterized by higher precipitation and in conditions of higher system productivity. Conclusion: we may conclude that the Mandacaru stream, although strongly influenced by anthropic action, still presents an acceptable water quality. Lastly, we emphasize that protists abundance was strongly influenced by system productivity. This was evidenced by elevated protozoan densities where there was higher primary and bacterial productivity. Thus, these organisms must be considered in studies that aim at the identification of organisms that may indicate anthropic impacts and environmental quality.

Resumo O objetivo foi investigar, em escalas espacial e temporal, a abundância das comunidades de protozoários bem como os fatores intervenientes na estruturação das mesmas em um córrego urbano. Métodos: Amostras de água para análise de comunidades biológicas (amebas testáceas, ciliados e bactérias) e para análise de variáveis limnológicas foram tomadas no córrego Mandacaru localizado na Unidade de Conservação do Parque do Cinquentenário, na cidade de Maringá, Paraná State, Brasil, em dois períodos hidrológicos (seco e chuvoso). Calculamos o Índice de Qualidade de Água (IQA), o Índice de Estado Trófico (ETI) para fósforo e utilizamos uma Análise de Redundância (RDA) para verificar a influência de variáveis ambientais na comunidade de protozoários. Resultados: O IQA mostrou que a qualidade da água foi considerada boa em alguns pontos e considerada ruim em outros pontos, e o ETI para o fósforo classificou o córrego como mesotrófico na maioria dos locais amostrados (média entre 53,09 e 58,35). Foram identificados 19 táxons de amebas testáceas, pertencentes a seis famílias, sendo Difflugiidae, Centropyxidae e Arcellidae as mais especiosas, e 71 táxons de ciliados, distribuídos em 12 ordens, sendo Peniculida a ordem mais representativa, seguida por Euplotida. De acordo com a análise RDA, amostras do período seco foram caracterizadas por maiores valores de densidade bacteriana e concentrações de clorofila-a, fósforo total e nitrogênio total. As amebas testáceas e os ciliados apresentaram valores de abundância maiores em alguns dos meses caracterizados por maior precipitação e em condições de maior produtividade do sistema. Podemos concluir que o córrego Mandacaru, embora fortemente influenciado pela ação antrópica, ainda apresenta uma qualidade de água aceitável. Por fim, enfatizamos que a abundância de protistas foi fortemente influenciada pela produtividade do sistema. Isto foi evidenciado pelas elevadas densidades de protozoários onde houve maior produtividade primária e bacteriana. Assim, esses protistas devem ser considerados em estudos que visem à identificação de organismos que possam indicar impactos antrópicos e qualidade ambiental.

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The aim of this study was to elaborate a taxonomic survey on the testate amoebae of the Family Arcellidaein coastal streams in the State of Rio de Janeiro. Six samplingswere conducted in Ubatiba coastal stream (Maricá, RJ). In total, 130 liters water were filtered through a conical net of 60-μm mesh and preserved in 4% formalin. Organisms were identified with the aid of an inverted trinocular microscope. The morphological characteristics (lobose testate amoebae with shell composed of granular chitinoid elements) of each species were recorded. The species were described and illustrated. For the verification of new taxa records of Arcellidae in Rio de Janeiro and their distribution in Brazil, a search based on indexarticles by Scopus, Web of Science and Google Scholar using the keywords "tecamebas", "testate amoebae", "Arcella", "Arcellidae", "Brazil" and "Rio de Janeiro", was performed. Eight Arcellidaespecies were recorded. Some ecological and taxonomic information was provided. Due to the small amount of information on testate amoebae, this study is important because it reduces the knowledge gap regarding this community in the State of Rio de Janeiro. Furthermore, we suggest new studies on species identification to be conducted to expand regional knowledge about these organisms.

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Abstract We aimed to investigate spatial and temporal scales, abundance, and factors that structure the communities of protozoans in a tropical urban stream. Methods: Samples of water for analysis of biological communities (testate amoebae, ciliates and bacteria) and limnological variables were taken in the Mandacaru stream located in the Conservation Unit of Parque do Cinquentenário, in the city of Maringá, Paraná State, Brazil, in two hydrological periods (dry and rainy). We calculated the Water Quality Index (WQI) composed by nine parameters of water quality (dissolved oxygen, thermotolerant coliforms, pH, BOD, water temperature, total nitrogen, total phosphorous, turbidity, and total solids), Trophic State Index (TSI) for phosphorous and we used a Redundancy Analysis (RDA) to verify the influence of environmental variables in the protozoan community. Results: The WQI showed that water quality was considered good in some points and considered bad in other points. The TSI for phosphorus classified the stream as mesotrophic in the majority of sampled sites points (mean between 53.09 and 58.35). We identified 19 taxa of testate amoebae, belonging to six families, being Difflugiidae, Centropyxidae, and Arcellidae those with more species and 71 infrageneric taxa of ciliates, distributed in 12 orders being Peniculida the most representative order, followed by Euplotida. According to RDA analysis, samples of the dry period were characterized by higher values of bacteria density and concentrations of chlorophyll-a, total phosphorous, and total nitrogen. Ciliates and testate amoebae presented higher abundance values in some of the months characterized by higher precipitation and in conditions of higher system productivity. Conclusion: we may conclude that the Mandacaru stream, although strongly influenced by anthropic action, still presents an acceptable water quality. Lastly, we emphasize that protists abundance was strongly influenced by system productivity. This was evidenced by elevated protozoan densities where there was higher primary and bacterial productivity. Thus, these organisms must be considered in studies that aim at the identification of organisms that may indicate anthropic impacts and environmental quality.

Resumo O objetivo foi investigar, em escalas espacial e temporal, a abundância das comunidades de protozoários bem como os fatores intervenientes na estruturação das mesmas em um córrego urbano. Métodos: Amostras de água para análise de comunidades biológicas (amebas testáceas, ciliados e bactérias) e para análise de variáveis limnológicas foram tomadas no córrego Mandacaru localizado na Unidade de Conservação do Parque do Cinquentenário, na cidade de Maringá, Paraná State, Brasil, em dois períodos hidrológicos (seco e chuvoso). Calculamos o Índice de Qualidade de Água (IQA), o Índice de Estado Trófico (ETI) para fósforo e utilizamos uma Análise de Redundância (RDA) para verificar a influência de variáveis ambientais na comunidade de protozoários. Resultados: O IQA mostrou que a qualidade da água foi considerada boa em alguns pontos e considerada ruim em outros pontos, e o ETI para o fósforo classificou o córrego como mesotrófico na maioria dos locais amostrados (média entre 53,09 e 58,35). Foram identificados 19 táxons de amebas testáceas, pertencentes a seis famílias, sendo Difflugiidae, Centropyxidae e Arcellidae as mais especiosas, e 71 táxons de ciliados, distribuídos em 12 ordens, sendo Peniculida a ordem mais representativa, seguida por Euplotida. De acordo com a análise RDA, amostras do período seco foram caracterizadas por maiores valores de densidade bacteriana e concentrações de clorofila-a, fósforo total e nitrogênio total. As amebas testáceas e os ciliados apresentaram valores de abundância maiores em alguns dos meses caracterizados por maior precipitação e em condições de maior produtividade do sistema. Podemos concluir que o córrego Mandacaru, embora fortemente influenciado pela ação antrópica, ainda apresenta uma qualidade de água aceitável. Por fim, enfatizamos que a abundância de protistas foi fortemente influenciada pela produtividade do sistema. Isto foi evidenciado pelas elevadas densidades de protozoários onde houve maior produtividade primária e bacteriana. Assim, esses protistas devem ser considerados em estudos que visem à identificação de organismos que possam indicar impactos antrópicos e qualidade ambiental.

RESUMO

To date there have only been two studies using testate amoebae as palaeoecological indicators in tropical peatlands. Here we present a new ∼500-year testate amoeba record from San Jorge, a domed peatland in Peruvian Amazonia, which has a well-constrained vegetation history based on pollen analysis. We observe a major shift from Hyalosphenia subflava to Cryptodifflugia oviformis-dominated communities at ∼50 cm depth (c. AD 1760), which suggests a change to drier conditions in the peatland. The application of a statistical transfer function also suggests a deepening of the water table at this time. The transition in the microbial assemblage occurs at a time when pollen and geochemical data indicate drier conditions (reduced influence of river flooding), leading to an ecosystem switch to more ombrotrophic-like conditions in the peatland. Our work illustrates the potential of testate amoebae as important tools in tropical peatland palaeoecology, and the power of multiproxy approaches for understanding the long-term development of tropical peatlands.

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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 2221m.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.

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We investigated the role of leaf litter chemistry and richness in affecting testate amoeba communities of tropical rainforest in the Ecuadorian Andes. Litterbags containing leaf litter from four dominating tree species (Clusia sp., Myrcia pubescens, Graffenrieda emarginata, and Cecropia andina) with richness 1, 2, and 4 species were established and exposed in the field for 12 months at 2000 m a.s.l. Chemical elements and compounds of leaf litter were analyzed before exposure. At the end of exposure, microbial biomass and litter mass loss were measured, and living testate amoeba species number, density, biomass, and community composition were determined. In total, 125 testate amoeba species colonized the litter in litterbags. The results suggest that high litter nitrogen and low lignin concentrations are indicators of high litter quality for testate amoebae density and species richness. Their species number and density significantly declined in the order 1 > 4 > 2 leaf litter species and varied with leaf litter chemistry being at a maximum in high-quality single leaf litter species and low in low-quality leaf litter. Further, the addition of litter of high-quality to low-quality litter increased testate amoebae biomass and density; however, the values did not exceed the ones in single high-quality litter treatments. Moreover, the structure of testate amoeba communities varied with litter chemistry, with Fe, Na, lignin, and litter C-to-N ratio being of major importance, and indicating that litter chemistry reflects habitat quality for testate amoebae. Overall, the data show that leaf litter chemistry overrides leaf litter richness in structuring testate amoeba communities.

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RESUMO

Testate amoebae are eukaryotic microorganisms characterized by the presence of an external shell (test). The shell morphology is used as a diagnostic character, but discordance between morphological and molecular data has been demonstrated in groups of arcellinids (Amoebozoa), one of the principal groups of testate amoebae. Morphology of the test is supposed to differentiate genera and species and it is applied in ecological, monitoring and paleontological studies. However, if phenotype does not reflect genotype, conclusions in these types of studies become severely impaired. The objective of this work is to evaluate the morphometrical and morphological variation of the closely related and morphologically similar taxa Arcella intermedia laevis Tsyganov and Mazei, 2006 and Arcella intermedia (Deflandre 1928) Tsyganov and Mazei, 2006 in nature and in cultured individuals and see how these are correlated with molecular data. Our results demonstrate that phenotypic plasticity in Arcella intermedia make morphological distinctions impossible in both taxa. Arcella intermedia and Arcella intermedia laevis are molecularly identical for SSU rDNA and a mitochondrial molecular marker (NAD9/7). We conclude that morphological techniques alone cannot identify phenotypic plasticity from natural populations. More work is clearly needed to better understand the morphological, morphometric and molecular variability in these organisms.

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RESUMO

Abstract We aimed to investigate spatial and temporal scales, abundance, and factors that structure the communities of protozoans in a tropical urban stream. Methods: Samples of water for analysis of biological communities (testate amoebae, ciliates and bacteria) and limnological variables were taken in the Mandacaru stream located in the Conservation Unit of Parque do Cinquentenário, in the city of Maringá, Paraná State, Brazil, in two hydrological periods (dry and rainy). We calculated the Water Quality Index (WQI) composed by nine parameters of water quality (dissolved oxygen, thermotolerant coliforms, pH, BOD, water temperature, total nitrogen, total phosphorous, turbidity, and total solids), Trophic State Index (TSI) for phosphorous and we used a Redundancy Analysis (RDA) to verify the influence of environmental variables in the protozoan community. Results: The WQI showed that water quality was considered good in some points and considered bad in other points. The TSI for phosphorus classified the stream as mesotrophic in the majority of sampled sites points (mean between 53.09 and 58.35). We identified 19 taxa of testate amoebae, belonging to six families, being Difflugiidae, Centropyxidae, and Arcellidae those with more species and 71 infrageneric taxa of ciliates, distributed in 12 orders being Peniculida the most representative order, followed by Euplotida. According to RDA analysis, samples of the dry period were characterized by higher values of bacteria density and concentrations of chlorophyll-a, total phosphorous, and total nitrogen. Ciliates and testate amoebae presented higher abundance values in some of the months characterized by higher precipitation and in conditions of higher system productivity. Conclusion: we may conclude that the Mandacaru stream, although strongly influenced by anthropic action, still presents an acceptable water quality. Lastly, we emphasize that protists abundance was strongly influenced by system productivity. This was evidenced by elevated protozoan densities where there was higher primary and bacterial productivity. Thus, these organisms must be considered in studies that aim at the identification of organisms that may indicate anthropic impacts and environmental quality.

Resumo O objetivo foi investigar, em escalas espacial e temporal, a abundância das comunidades de protozoários bem como os fatores intervenientes na estruturação das mesmas em um córrego urbano. Métodos: Amostras de água para análise de comunidades biológicas (amebas testáceas, ciliados e bactérias) e para análise de variáveis limnológicas foram tomadas no córrego Mandacaru localizado na Unidade de Conservação do Parque do Cinquentenário, na cidade de Maringá, Paraná State, Brasil, em dois períodos hidrológicos (seco e chuvoso). Calculamos o Índice de Qualidade de Água (IQA), o Índice de Estado Trófico (ETI) para fósforo e utilizamos uma Análise de Redundância (RDA) para verificar a influência de variáveis ambientais na comunidade de protozoários. Resultados: O IQA mostrou que a qualidade da água foi considerada boa em alguns pontos e considerada ruim em outros pontos, e o ETI para o fósforo classificou o córrego como mesotrófico na maioria dos locais amostrados (média entre 53,09 e 58,35). Foram identificados 19 táxons de amebas testáceas, pertencentes a seis famílias, sendo Difflugiidae, Centropyxidae e Arcellidae as mais especiosas, e 71 táxons de ciliados, distribuídos em 12 ordens, sendo Peniculida a ordem mais representativa, seguida por Euplotida. De acordo com a análise RDA, amostras do período seco foram caracterizadas por maiores valores de densidade bacteriana e concentrações de clorofila-a, fósforo total e nitrogênio total. As amebas testáceas e os ciliados apresentaram valores de abundância maiores em alguns dos meses caracterizados por maior precipitação e em condições de maior produtividade do sistema. Podemos concluir que o córrego Mandacaru, embora fortemente influenciado pela ação antrópica, ainda apresenta uma qualidade de água aceitável. Por fim, enfatizamos que a abundância de protistas foi fortemente influenciada pela produtividade do sistema. Isto foi evidenciado pelas elevadas densidades de protozoários onde houve maior produtividade primária e bacteriana. Assim, esses protistas devem ser considerados em estudos que visem à identificação de organismos que possam indicar impactos antrópicos e qualidade ambiental.

RESUMO

Testate amoebae are a polyphyletic assemblage of at least three major, unrelated taxonomic groups of unicellular amoeboid eukaryotes exhibiting a test. The focus on testate amoebae in scientific research has greatly increased in the past 20 years: from an average of about 5 papers a year in the mid-1990s to the current rate of more than 50 papers published yearly. The application range of these organisms is rapidly expanding as well: from the traditional fields of environmental monitoring and paleoecology, to forensic sciences and ecotoxicology studies. These developments are nevertheless strongly dependent on reliable taxonomy and nomenclature. However, scientometric data reveal that despite an ever-increasing necessity for the use of names (the product of taxonomy), the corresponding effort has not been achieved for improving testate amoebae systematics. As a consequence, inaccurate taxonomy yields to misinterpretations in the diversity of the organisms and to potentially incorrect conclusions. These and related problems are discussed in this study, highlighting the outcome of poor taxonomic expertise in accurate classification and phylogeny of testate amoebae, and the consequences derived from it. Additionally, this study is aimed to discuss the current status of testate amoebae classification, and to present all nomenclature and taxonomic changes in higher and lower taxonomic levels of testate amoebae, as a result of recent molecular reconstructions. Finally, we conclude with a list of the needs and suggestions toward a unified and modernized taxonomy of testate amoebae.

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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 125cm, 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.

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There has only been one study on the ecology of testate amoebae from Amazonian peatlands, despite Amazonia being a biodiversity hotspot of global importance. During analysis of litter samples from Aucayacu peatland, western (Peruvian) Amazonia, we discovered a testate amoeba with a distinct morphology unlike any other species reported previously. We describe a new species, Arcella peruviana, based on its distinct morphology, compare it to morphologically similar species and provide information about its ecology. This new species is characterised by a distinct cruciform aperture (diameter ranges between 12 and 17µm) which is slightly invaginated. The test is small (height 43-57µm) and polygonal in cross-section. Our discovery suggests the existence of an unknown diversity of testate amoebae in Amazonia. The absence of the new Arcella species in more intensively-sampled regions supports the view that protists have restricted distributions.

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The use of substitute groups in biomonitoring programs has been proposed to minimize the high financial costs and time for samples processing. The objectives of this study were to evaluate the correlation between (i) the spatial distribution among the major zooplankton groups (cladocerans, copepods, rotifers, and testaceans protozoa), (ii) the data of density and presence/absence of species, and (iii) the data of species, genera, and families from samples collected in the Lago Grande do Curuai, Pará, Brazil. A total of 55 sample of the zooplanktonic community was collected, with 28 samples obtained in March and 27 in September, 2013. The agreement between the different sets of data was assessed using Mantel and Procrustes tests. Our results indicated high correlations between genus level and species level and high correlations between presence/absence of species and abundance, regardless of the seasonal period. These results suggest that zooplankton community could be incorporated in a long-term monitoring program at relatively low financial and time costs.(AU)

O uso de grupos substitutos em programas de biomonitoramento tem sido proposto para minimizar os altos custos financeiros e tempo para processamento das amostras. Os objetivos deste estudo foram avaliar a correlação entre (i) a distribuição espacial nos principais grupos zooplanctônicos (cladóceros, copépodes, protozoários testáceos e rotíferos), (ii) os dados de densidade e presença/ausência de espécies, e (iii) os dados de espécies, gêneros e famílias a partir de amostras coletadas no Lago Grande do Curai, Pará, Brasil. Um total de 55 amostras da comunidade zooplanctônica foi coletada, sendo 28 em março e 27 em setembro de 2013. A concordância entre os diferentes conjuntos de dados foi avaliada por meio dos testes de Mantel e Procrustes. Nossos resultados indicam alta correlação entre nível de gênero e espécies e entre a presença/ausência de espécies e abundância, independentemente do período sazonal. Estes resultados sugerem que a comunidade zooplanctônica pode ser incorporada em programas de monitoramento a longo prazo com custos financeiros e de tempo relativamente menores.(AU)

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RESUMO

The use of substitute groups in biomonitoring programs has been proposed to minimize the high financial costs and time for samples processing. The objectives of this study were to evaluate the correlation between (i) the spatial distribution among the major zooplankton groups (cladocerans, copepods, rotifers, and testaceans protozoa), (ii) the data of density and presence/absence of species, and (iii) the data of species, genera, and families from samples collected in the Lago Grande do Curuai, Pará, Brazil. A total of 55 sample of the zooplanktonic community was collected, with 28 samples obtained in March and 27 in September, 2013. The agreement between the different sets of data was assessed using Mantel and Procrustes tests. Our results indicated high correlations between genus level and species level and high correlations between presence/absence of species and abundance, regardless of the seasonal period. These results suggest that zooplankton community could be incorporated in a long-term monitoring program at relatively low financial and time costs.

O uso de grupos substitutos em programas de biomonitoramento tem sido proposto para minimizar os altos custos financeiros e tempo para processamento das amostras. Os objetivos deste estudo foram avaliar a correlação entre (i) a distribuição espacial nos principais grupos zooplanctônicos (cladóceros, copépodes, protozoários testáceos e rotíferos), (ii) os dados de densidade e presença/ausência de espécies, e (iii) os dados de espécies, gêneros e famílias a partir de amostras coletadas no Lago Grande do Curai, Pará, Brasil. Um total de 55 amostras da comunidade zooplanctônica foi coletada, sendo 28 em março e 27 em setembro de 2013. A concordância entre os diferentes conjuntos de dados foi avaliada por meio dos testes de Mantel e Procrustes. Nossos resultados indicam alta correlação entre nível de gênero e espécies e entre a presença/ausência de espécies e abundância, independentemente do período sazonal. Estes resultados sugerem que a comunidade zooplanctônica pode ser incorporada em programas de monitoramento a longo prazo com custos financeiros e de tempo relativamente menores.

Assuntos

RESUMO

The terrestrial cycling of Si is thought to have a large influence on the terrestrial and marine primary production, as well as the coupled biogeochemical cycles of Si and C. Biomineralization of silica is widespread among terrestrial eukaryotes such as plants, soil diatoms, freshwater sponges, silicifying flagellates and testate amoebae. Two major groups of testate (shelled) amoebae, arcellinids and euglyphids, produce their own silica particles to construct shells. The two are unrelated phylogenetically and acquired biomineralizing capabilities independently. Hyalosphenids, a group within arcellinids, are predators of euglyphids. We demonstrate that hyalosphenids can construct shells using silica scales mineralized by the euglyphids. Parsimony analyses of the current hyalosphenid phylogeny indicate that the ability to "steal" euglyphid scales is most likely ancestral in hyalosphenids, implying that euglyphids should be older than hyalosphenids. However, exactly when euglyphids arose is uncertain. Current fossil record contains unambiguous euglyphid fossils that are as old as 50 million years, but older fossils are scarce and difficult to interpret. Poor taxon sampling of euglyphids has also prevented the development of molecular clocks. Here, we present a novel molecular clock reconstruction for arcellinids and consider the uncertainties due to various previously used calibration points. The new molecular clock puts the origin of hyalosphenids in the early Carboniferous (∼370 mya). Notably, this estimate coincides with the widespread colonization of land by Si-accumulating plants, suggesting possible links between the evolution of Arcellinid testate amoebae and the expansion of terrestrial habitats rich in organic matter and bioavailable Si.

RESUMO

The seasonal variation of the protozooplanktonic community (ciliates and testate amoebae) was studied in a tropical oligotrophic reservoir in Brazil, which was under the influence of two contrasting climatic seasons (rainy/warm and dry/cold). The aim of this study was to evaluate the effect of these climatic changes on physical, chemical and biological variables in the dynamic of this community. The highest mean density of total protozoans occurred in the rainy/warm season (5683.2 ind L−1), while the lowest was in the dry/cold (2016.0 ind L−1). Considering the seasonal variations, the protozoan groups that are truly planktonic, such as the oligotrichs (Spirotrichea), predominated in the dry season, whereas during the rainy season, due to the material input and resuspension of sediment, sessile protozoans of the Peritrichia group were the most important ones. The dominant protozoans were Urotricha globosa, Cothurnia annulata, Pseudodifflugia sp. and Halteria grandinella. The highest densities of H. grandinella were associated with more oxygenated and transparent water conditions, while the highest densities of C. annulata occurred in sites with high turbidity, pH and trophic state index (TSI). The study demonstrated that density and composition of protozooplanktonic species and groups of the reservoir suffered seasonal variation due to the environmental variables (mainly temperature, turbidity, water transparency, dissolved oxygen and TSI) and the biological variables (e.g. morphological characteristics, eating habits and escape strategies from predation of the species).

A variação sazonal da comunidade protozooplanctônica (ciliados e amebas testáceas) foi estudada em um reservatório oligotrófico tropical no Brasil, que estava sob a influência de dois períodos climáticos contrastantes (chuvoso/quente e seco/frio). O objetivo deste estudo foi avaliar os efeitos destas mudanças climáticas sobre as variáveis físicas, químicas e biológicas na dinâmica desta comunidade. A maior densidade média de protozoários total ocorreu no período chuvoso e quente (5683,2 ind L−1), enquanto a menor foi no período seco e frio (2016,0 ind L−1). Considerando-se as variações sazonais, os grupos de protozoários que são verdadeiramente planctônicos, como os oligotrichs (Spirotrichea), predominaram no período seco, enquanto que, no período chuvoso, em razão da entrada de material e da ressuspensão do sedimento, os protozoários sésseis do grupo Peritrichia foram os mais importantes. Os protozoários dominantes foram Urotricha globosa, Cothurnia annulata, Pseudodifflugia sp. e Halteria grandinella. As maiores densidades de H. grandinella foram associadas com condições de águas mais oxigenadas e transparentes, enquanto que as maiores densidades de C. annulata ocorreram em locais com alta turbidez, pH e índice de estado trófico (IET). O estudo demonstrou que a densidade e a composição de espécies, e os grupos protozooplanctônicos do reservatório sofreram variação sazonal por causa das variáveis ambientais – principalmente temperatura, além de turbidez, transparência da água, oxigênio dissolvido e IET – e das variáveis biológicas, como, por exemplos, características morfológicas, hábitos alimentares e estratégias de escape à predação das espécies.

Assuntos

RESUMO

The seasonal variation of the protozooplanktonic community (ciliates and testate amoebae) was studied in a tropical oligotrophic reservoir in Brazil, which was under the influence of two contrasting climatic seasons (rainy/warm and dry/cold). The aim of this study was to evaluate the effect of these climatic changes on physical, chemical and biological variables in the dynamic of this community. The highest mean density of total protozoans occurred in the rainy/warm season (5683.2 ind L1), while the lowest was in the dry/cold (2016.0 ind L1). Considering the seasonal variations, the protozoan groups that are truly planktonic, such as the oligotrichs (Spirotrichea), predominated in the dry season, whereas during the rainy season, due to the material input and resuspension of sediment, sessile protozoans of the Peritrichia group were the most important ones. The dominant protozoans were Urotricha globosa, Cothurnia annulata, Pseudodifflugia sp. and Halteria grandinella. The highest densities of H. grandinella were associated with more oxygenated and transparent water conditions, while the highest densities of C. annulata occurred in sites with high turbidity, pH and trophic state index (TSI). The study demonstrated that density and composition of protozooplanktonic species and groups of the reservoir suffered seasonal variation due to the environmental variables (mainly temperature, turbidity, water transparency, dissolved oxygen and TSI) and the biological variables (e.g. morphological characteristics, eating habits and escape strategies from predation of the species).(AU)

A variação sazonal da comunidade protozooplanctônica (ciliados e amebas testáceas) foi estudada em um reservatório oligotrófico tropical no Brasil, que estava sob a influência de dois períodos climáticos contrastantes (chuvoso/quente e seco/frio). O objetivo deste estudo foi avaliar os efeitos destas mudanças climáticas sobre as variáveis físicas, químicas e biológicas na dinâmica desta comunidade. A maior densidade média de protozoários total ocorreu no período chuvoso e quente (5683,2 ind L1), enquanto a menor foi no período seco e frio (2016,0 ind L1). Considerando-se as variações sazonais, os grupos de protozoários que são verdadeiramente planctônicos, como os oligotrichs (Spirotrichea), predominaram no período seco, enquanto que, no período chuvoso, em razão da entrada de material e da ressuspensão do sedimento, os protozoários sésseis do grupo Peritrichia foram os mais importantes. Os protozoários dominantes foram Urotricha globosa, Cothurnia annulata, Pseudodifflugia sp. e Halteria grandinella. As maiores densidades de H. grandinella foram associadas com condições de águas mais oxigenadas e transparentes, enquanto que as maiores densidades de C. annulata ocorreram em locais com alta turbidez, pH e índice de estado trófico (IET). O estudo demonstrou que a densidade e a composição de espécies, e os grupos protozooplanctônicos do reservatório sofreram variação sazonal por causa das variáveis ambientais principalmente temperatura, além de turbidez, transparência da água, oxigênio dissolvido e IET e das variáveis biológicas, como, por exemplos, características morfológicas, hábitos alimentares e estratégias de escape à predação das espécies.(AU)

Assuntos