Upstream cascade reservoirs drive temporal beta diversity increases through species loss in a dammed river.

Changes in the biodiversity of aquatic environments over time and space due to human activities are a topic of theoretical and conservational interest in ecology. Thus, variation in taxonomic beta diversity of the planktonic ciliates community was investigated along a temporal and spatial gradient in two subsystems of a Neotropical floodplain, one impacted by dams (Paraná) and the other free of them along its course (Ivinhema). For the spatial analysis, the Paraná subsystem did not show a significant decrease in beta diversity, presenting a pattern like that observed for the Ivinhema subsystem. Therefore, biotic homogenization was not observed for the ciliate's community downstream of the dams. It was noted that there was a fluctuation in the relevance of the components of beta diversity, regardless of the subsystem analyzed. For the temporal analysis there was a significant change in species composition from the first to the last year investigated, essentially for the subsystem impacted by dams, and that this was determined mainly by species loss. Although spatial beta diversity remained high without a clear process of biotic homogenization, dams promoted remarkable changes in ciliate species composition over the years mainly by continuous loss of species.

Influence of Ecological Multiparameters on Facets of ß-Diversity of Freshwater Plankton Ciliates.

Understanding the relative importance of the factors that drive global patterns of biodiversity is among the major topics of ecological and biogeographic research. In freshwater bodies, spatial, temporal, abiotic, and biotic factors are important structurers of these ecosystems and can trigger distinct responses according to the facet of biodiversity considered. The objective was to evaluate how different facets of ß-diversity (taxonomic, functional, and phylogenetic) based on data from the planktonic ciliate community of a Neotropical floodplain, are influenced by temporal, spatial, abiotic, and biotic factors. The research was conducted in the upper Paraná River floodplain between the years 2010 and 2020 in different water bodies. All predictors showed significant importance on the facets of ß-diversity, except the abiotic predictors on species composition data, for the taxonomic facet. The functional and phylogenetic facets were mostly influenced by abiotic, biotic, and spatial factors. For temporal predictors, results showed influence on taxonomic (structure and composition data) and functional (structure data) facets. Also, a fraction of shared explanation between the temporal and abiotic components was observed for the distinct facets. Significant declines in ß-diversity in continental ecosystems have been evidenced, especially those with drastic implications for ecosystemic services. Therefore, the preservation of a high level of diversity in water bodies, also involving phylogenetic and functional facets, should be a priority in conservation plans and goals, to ensure the maintenance of important ecological processes involving ciliates.

Experimental evaluation of microplastic consumption by using a size-fractionation approach in the planktonic communities.

The increasing amount of plastic particles introduced into continental aquatic environments has drawn the attention of researchers around the globe. These particles can be assimilated by a wide range of aquatic organisms, from microorganisms to fish, causing detrimental effects on trophic webs. Using an experimental approach, we investigated the effect of microplastic particles of different sizes on the planktonic trophic chain by sampling natural plankton communities from a lake located in the Upper Paraná River floodplain, Brazil. Zooplankton samples were collected at the beginning of the experiment and after 36 h of incubation. Microplastic particles (MP) samples were taken every 12 h. The effect of MP particle consumption from the control and treatment groups indicates significant effects by all plankton size fractions (p < 0.05). We demonstrated that the presence of MP particles can significantly affect the trophic web, furthermore, we detected the effect of higher consumption effect of smaller size MP particles. This study suggest that the largest MP consumption effects come from the lower trophic levels of the trophic chain, such as protists. The competitive effect of large predators is a crucial factor in controlling the abundance of populations, and although they did not directly consume MP particles, they ingest them indirectly through prey capable of absorbing these compounds in the environment. Our findings warn that MP particles enter the food webs of tropical regions when exposed to these pollutants, and that the presence of these particles should not be neglected when studying freshwater ecosystems.

Impoundment, environmental variables and temporal scale predict zooplankton beta diversity patterns in an Amazonian river basin.

The implementation of environmental monitoring programs in areas under anthropogenic pressure is essential to investigate the processes that generate and maintain biodiversity in ecosystems and to establish the most appropriate conservation strategies according to the area. We investigated whether environmental variables or temporal scale influenced zooplankton spatial diversity and beta diversity components in the Madeira River basin (Amazon tributary, Rondônia state, Brazil) from 2009 to 2015. We also investigated the local site contribution to overall beta diversity (LCBD) and to each of its components, to be able to propose conservation strategies more suitable for the river basin. Alpha diversity values decreased over time, while total beta diversity and the abundance difference component increased. A pattern of abundance difference (Podani family) dominated spatial beta diversity within the major sampling campaigns (at each time point). Environmental variables and heterogeneity, temporal scale (sampling campaigns), and also the dam installation contributed to variation in spatial beta diversity and its components. On the other hand, the flood pulse did not influence spatial beta diversity over time. Few sites contributed significantly to beta diversity prior dam installation, but most sites contributed significantly to beta diversity values at least at one point in time, in the post-dam phase. Thus, post-damming, all sites should continue to be monitored for conservation and restoration of zooplankton communities and biodiversity preservation, as changes are likely to still occur. Analysis of beta diversity, its components, and LCBD, are useful and efficient methods to study spatio-temporal changes in communities and identify critical sites. Impoundment and environmental variation significantly affect zooplankton community beta diversity, dependent on underlying mechanisms such as substitution or abundance differences that diversify communities spatially and temporally.

Protist Biodiversity and Biogeography in Lakes From Four Brazilian River-Floodplain Systems.

The biodiversity and biogeography of protists inhabiting many ecosystems have been intensely studied using different sequencing approaches, but tropical ecosystems are relatively under-studied. Here, we sampled planktonic waters from 32 lakes associated with four different river-floodplains systems in Brazil, and sequenced the DNA using a metabarcoding approach with general eukaryotic primers. The lakes were dominated by the largely free-living Discoba (mostly the Euglenida), Ciliophora, and Ochrophyta. There was low community similarity between lakes even within the same river-floodplain. The protists inhabiting these floodplain systems comprise part of the large and relatively undiscovered diversity in the tropics.

Common and Rare Taxa of Planktonic Ciliates: Influence of Flood Events and Biogeographic Patterns in Neotropical Floodplains.

After much discussion about the cosmopolitan nature of microbes, the great issue nowadays is to identify at which spatial extent microorganisms may display biogeographic patterns and if temporal variation is important in altering those patterns. Here, planktonic ciliates were sampled from shallow lakes of four Neotropical floodplains, distributed over a spatial extent of ca. 3000 km, during high and low water periods, along with several abiotic and biotic variables potentially affecting the ciliate community. We found that common ciliate species were more associated with environmental gradients and rare species were more related to spatial variables; however, this pattern seemed to change depending on the temporal and spatial scales considered. Environmental gradients were more important in the high waters for both common and rare species. In low waters, common species continued to be mainly driven by environmental conditions, but rare species were more associated with the spatial component, suggesting dispersal limitation likely due to differences in dispersal ability and ecological tolerance of species. We also found that common and rare species were related to different environmental variables, suggesting different ecological niches. At the largest spatial extents, rare species showed clear biogeographic patterns.

Relationships between environmental conditions and the morphological variability of planktonic testate amoeba in four neotropical floodplains.

Planktonic testate amoebae in floodplains exhibit a broad-range of morphological variability. The variation size is already known, but it is necessary to know how this is for morphological variables. This study aimed to identify the relationships between testate amoebae morphology and environmental factors in four neotropical floodplains. We conducted detailed morphometric analyses on 27 common species of planktonic testate amoebae from genera Arcella, Centropyxis, Cucurbitella, Suiadifflugia, Difflugia, Lesquereusia and Netzelia. We sampled subsurface water from each lake in 72 lakes in four Brazilian floodplain lakes. Our goals were to assess: (1) the range of their morphological variability (a) over space within each floodplain, and (b) among the four floodplains, and (c) over time, and (2) which environmental factors explained this variation. Mean shell height and breadth varied considerably among the different floodplain lakes, especially in the Pantanal and Amazonian floodplains. The morphological variability of testate amoeba was correlated to environmental conditions (ammonia, nitrate, phosphate, chlorophyll-a, turbidity, temperature, and depth). Thus, understanding the morphological variation of the testate amoeba species can elucidate many questions involving the ecology of these organisms. Furthermore, could help molecular studies, bioindicator role of these organisations, environmental reconstruction, among others.

Anthropogenic disturbances influencing ciliate functional feeding groups in impacted tropical streams.

Anthropogenic disturbances change the trophic structure of streams, ultimately affecting ecosystem functioning. We investigated the effects of human disturbances, mainly organic pollution, on ciliate functional feeding groups (FFG) in 10 tropical streams near agricultural and urban habitats, in the dry and rainy seasons. We hypothesised that the organic pollution would affect the ciliate composition and that the richness and abundance of ciliate FFG would be associated with different disturbances, such that an increase in the load of organic matter would result in an increase in the percentage of bacterivores ciliates, while streams with low organic matter concentration and wide canopy openness will determine a higher contribution of algivorous ciliates. Our results corroborate our hypothesis of an increased development of bacterivorous ciliates with increasing organic pollution, but only in the abundance of this FFG. Also, algivorous ciliates were found to be related to riparian vegetation clearing. Thus, ciliate FFG accurately reflected different anthropogenic disturbances, revealing a change in the trophic structure of the streams. In addition, we found that organic pollution can lead to both taxonomic and functional homogenization of the ciliate community, which implies serious consequences for ecosystem functioning.

The role of microorganisms in a planktonic food web of a floodplain lake.

Food webs include complex ecological interactions that define the flow of matter and energy, and are fundamental in understanding the functioning of an ecosystem. Temporal variations in the densities of communities belonging to the planktonic food web (i.e., microbial: bacteria, flagellate, and ciliate; and grazing: zooplankton and phytoplankton) were investigated, aiming to clarify the interactions between these organisms and the dynamics of the planktonic food web in a floodplain lake. We hypothesized that hydrological pulse determines the path of matter and energy flow through the planktonic food web of this floodplain lake. Data were collected monthly from March 2007 to February 2008 at three different sites in Guaraná Lake (Mato Grosso do Sul State, Brazil). The path analysis provided evidence that the dynamics of the planktonic food web was strongly influenced by the hydrological pulse. The high-water period favored interactions among the organisms of the microbial loop, rather than their relationships with zooplankton and phytoplankton. Therefore, in this period, the strong interaction among the organisms of the grazing food chain suggests that the microbial loop functions as a sink of matter and energy. In turn, in the low-water period, higher primary productivity appeared to favor different interactions between the components of the grazing food chain and microorganisms, which would function as a link to the higher trophic levels.

Structure of planktonic ciliates community (Protist, Ciliophora) from an urban lake of southern Brazil / Estrutura da comunidade de ciliados planctônicos (Protista, Ciliophora) de um lago urbano do Sul do Brasil

This study examined temporal and spatial (vertical) variations of composition, richness and abundance of the planktonic ciliates community in an urban and eutrophic lake, as well as identified the limnological factors involved in determining the patterns observed. To this end, samples of ciliates and measures of limnological variables were taken at different depths and hydrological periods. 35 ciliate species were identified, among which 14 species occurred in all periods and strata, being Prostomatida the most specious, followed by Gymnostomatida, Oligotrichida, Peritrichida, and Scuticociliatida. The patterns found for composition, abundance and species richness evidenced a vertical and temporal variation of these attributes. However, in general the composition and species richness have varied more along the vertical gradient than between periods, whereas for the abundance, only temporal differences could be detected. Results observed herein indicated that benthic species seem to be mainly influenced by the amount of organic matter, phosphorus and ammonia, while planktonic ones, abundant at the surface, were mainly associated with higher dissolved oxygen concentrations. In this way, seasonal and vertical variations of limnological characteristics were decisive for the patterns of occurrence and abundance of ciliate species.

O presente estudo teve como objetivo investigar as variações temporais e espaciais (vertical) da composição, riqueza de espécies e abundância da comunidade de ciliados planctônicos em um lago urbano, eutrófico, e identificar alguns fatores limnológicos intervenientes na determinação dos padrões observados. Para tal, amostras de ciliados, bem como as mensurações das variáveis limnológicas foram obtidas em diferentes profundidades e períodos hidrológicos. Trinta e cinco espécies de ciliados foram identificadas, das quais 14 ocorreram em ambos os períodos e estratos. Prostomatida foi a ordem com maior número de espécies, seguida por Gymnostomatida, Oligotrichida, Peritrichida e Scuticociliatida. A composição e riqueza de espécies, em geral, variaram mais verticalmente que temporalmente, enquanto que para a abundância, diferenças foram observadas apenas entre os períodos hidrológicos Os resultados indicaram que espécies bentônicas parecem ser influenciadas principalmente pela quantidade de matéria orgânica, fósforo total e amônia, enquanto que as espécies planctônicas, abundantes na superfície, estiveram principalmente associadas com as maiores concentrações de oxigênio dissolvido. Desta forma, as variações sazonais e verticais das características limnológicas foram decisivas na determinação dos padrões de ocorrência e abundância de espécies de ciliados.

Flagellate protist abundance in phytotelmata of Aechmea distichantha Lem. (Bromeliaceae) in the upper Paraná river basin / Abundância de protozoários flagelados em fitotelmata de Aechmea distichantha Lem. (Bromeliaceae) na bacia do alto rio Paraná

In some Bromeliaceae species the leaf sheaths form a tank or phytotelma, accumulating water and organic detritus, conditions that allow the establishment of different communities. Thus, this study evaluated the relationship between diameter and volume of water in the tank of the bromeliad Aechmea distichantha Lem. and density of flagellates found in the phytotelmata, as well as the influence of the hydrological periods and proximity of sampled strata on the phytotelma patterns of abundance distribution. Samplings were conducted in two hydrological periods in 2010. In each sampling, four plants were collected from three different strata, classified according to the distance from the river level. A one-way ANOVA identified significant differences in flagellate density between hydrological periods. The influence of the water volume in the phytotelmata on the flagellate density was evidenced by regression analyses, as well as the lack of relationship between the density and perimeter of the tank. Moreover, the distance of the strata from the river level did not influence the pattern of flagellate abundance. Thus, our results suggested that the hydrological period and the volume of water in the tanks of Aechmea distichantha are determinant on the abundance of heterotrophic flagellate in the phytotelmata.

Em algumas Bromeliaceae as bainhas foliares formam uma cisterna ou fitotelma, onde ocorre acúmulo de água e detritos orgânicos, que permitem o estabelecimento de diferentes comunidades. Assim, este estudo avaliou a relação entre o diâmetro e volume de água no tanque de Aechmea distichantha Lem. e a abundância de flagelados encontrados nestes fitotelmata, bem como a influência do período hidrológico e a proximidade dos estratos amostrados sobre os padrões de distribuição desse atributo. As coletas foram realizadas em dois períodos hidrológicos no ano de 2010. Foram coletadas quatro plantas em três estratos diferentes de acordo com a distância em relação ao rio. Foram identificadas diferenças significativas entre a densidade dos flagelados e os períodos hidrológicos. Além disso, verificou-se a influência do volume de água presente nos fitotelmata sobre a densidade dos flagelados, bem como a ausência de relação entre a densidade desses protistas e o perímetro do tanque das bromélias. A distância dos distintos estratos em relação ao rio não influenciou a abundância dos flagelados. Assim, os resultados sugerem que o período hidrológico bem como o volume de água presente nos tanques de Aechmea distichantha atuam como um fator determinante sobre a abundância da comunidade de flagelados heterotróficos nos fitotelmata.

Size structure of testate amoebae (Arcellinida and Euglyphida) in different habitats from a lake in the upper Paraná River floodplain.

This study aimed to investigate the relationship between the size structure of testate amoebae in distinct habitats, i.e. plankton, aquatic macrophytes and aquatic sediment. The samples were taken from a floodplain lake of the upper Paraná River. The assumptions we strived to scrutinize were that (i) larger mean sizes of testate amoebae would be recorded in the sediment of the lake; and (ii) temporally, smaller individuals would be registered during the high water period in all habitats. The sampling was done monthly, from April 2007 to March 2008, in triplicates for each habitat. Testate amoebae were represented by individuals sized between 20 and 400 µm. The smaller individuals predominated in plankton samples, while in the aquatic sediment the larger ones were chiefly represented. These differences were probably associated with metabolic activities, i.e. the energy needs of these unicellular organisms, in each habitat. Two-way ANOVA yielded significant differences between hydrological periods. During the high water period, the increase in rainfall and consequently in water flow, decreased the stability of the system and increased turbulence and water column circulation. Therefore, environmental stability seems to be one of the main factors driving the temporal variation in the size structure of these specific organisms.

Species richness of testate amoebae in different environments from the upper Paraná river floodplain (PR/MS) / Riqueza de amebas testáceas em diferentes ambientes da planície de inundação do alto rio Paraná (PR/MS)

This study evaluated the species richness of testate amoebae in the plankton from different environments of the upper Paraná river floodplain. Samplings were performed at subsurface of pelagic region from twelve environments using motorized pump and plankton net (68 m), during four hydrological periods. We identified 67 taxa, distributed in seven families and Arcellidae, Difflugiidae and Centropyxidae were the most representative families. Higher values of species richness were observed in the lakes (connected and isolated) during the flood pulses. Centropyxis aculeata, Difflugia gramem and D. pseudogramem were frequent throughout the study period. Seasonal variability of species in the channels and isolated lakes was evidenced by beta diversity. Besides that, in the rivers, extreme changes in species composition were verified during the high-water period. Our results highlight the importance of the present study to improve the knowledge about the diversity and geographic distribution of these organisms in Brazil and emphasize the importance of current flow in the displacement of testate amoebae from their preferred habitats, marginal vegetation and sediment.

Este estudo objetivou avaliar a riqueza de táxons de amebas testáceas no plâncton de diferentes ambientes da planície de inundação do alto rio Paraná. Foram amostrados 12 pontos da região pelágica em diferentes ambientes (rios, canais e lagoas) e em quatro períodos hidrológicos. Foram identificados 67 táxons, distribuídos em sete famílias. Arcellidae, Difflugiidae e Centropyxidae foram as famílias mais especiosas. Nas lagoas (abertas e fechadas), durante os pulsos de inundação, foram observados os maiores valores para a riqueza de espécies. Centropyxis aculeata, Difflugia gramem e D. pseudogramem foram frequentes durante todo o período estudado. Os dados obtidos pela diversidade beta evidenciaram a variabilidade sazonal das espécies nos canais e lagoas fechadas. Nos rios, as alterações ocorreram com maior intensidade no período de cheia. Os resultados ressaltam a importância desse estudo para o acréscimo do conhecimento sobre a diversidade e distribuição geográfica desses organismos no Brasil e ratifica a importância do fluxo de corrente no carreamento de amebas testáceas de seus hábitats preferenciais, vegetação marginal e sedimento.

Longitudinal variation of attributes from flagellate protozoan community in tropical streams / Variação longitudinal dos atributos da comunidade de protozoários flagelados de riachos tropicais

This study verified the existence of longitudinal patterns in species composition, richness, density and biomass of flagellate protozoan in tropical streams and investigated whether the possible zonation patterns are different between two periods of the year. For this, samplings were carried out in three regions from 10 streams, during the summer and winter. The flagellate community may be considered species-rich, because it was represented by 106 taxa, belonging to 8 orders and 1 residual group. The values of density and biomass are greater than those commonly found in other lotic environments, with mean values close to 2.3x104 cels. mL-1 and 150.8 µgC L-1. We did not observe any conspicuous and significant longitudinal pattern of the attributes from flagellates community. Only temporal variations of these attributes were verified. The Pearson Correlation evidenced that this temporal patterns was mainly driven by the nutrients availability, temperature and dissolved oxygen, since, the higher values of species richness, density and biomass were recorded during the winter, when the higher concentrations of nutrients and dissolved oxygen and lower temperatures were registered. In summary, the absence of patterns may be ascribed to the unidirectional and continuous flow from lotic environments.

O presente estudo objetivou verificar a existência de padrões longitudinais de composição, riqueza de espécies, densidade e biomassa da comunidade de protozoários flagelados de riachos tropicais e, ainda, investigar se os possíveis padrões de zonação são diferentes entre dois períodos do ano. Foram realizadas coletas em três regiões ao longo de dez riachos, durante os períodos de verão e inverno. A comunidade de protozoários flagelados pode ser considerada bastante rica, sendo representada por 106 táxons pertencentes a oito ordens e um grupo residual. Os valores de densidade e biomassa registrados encontram-se acima dos valores comumente encontrados em outros ambientes lóticos, com valores médios próximos de 2,3x10 4 cels. mL-1 e 150,8 µgC L-1. Não foi verificado nenhum padrão longitudinal conspícuo e significativo dos atributos dessa comunidade. Foram verificadas apenas variações temporais destes atributos. As correlações de Pearson demonstraram que esse padrão temporal foi governado principalmente pela disponibilidade de nutrientes, temperatura e oxigênio dissolvido, visto que os maiores valores de riqueza, densidade e biomassa foram registrados no inverno, e também foram verificadas as maiores concentrações de nutrientes, de oxigênio dissolvido e as menores temperaturas. Em suma, sugere-se que essa ausência de padrões longitudinais pode ser atribuída ao fluxo unidirecional e contínuo dos ambientes lóticos.

Ciliate community associated with aquatic macrophyte roots: effects of nutrient enrichment on the community composition and species richness.

The objective of this study was to identify the impact of nutrient enrichment on the diversity of the ciliate community associated with the roots of the aquatic macrophyte Eichhornia crassipes. The experiment was performed in the Garças Lake, located in the Upper Paraná River floodplain, Brazil. We conducted two treatments (fertilized and control) with three replicates each. To increase the initial nutrient concentrations in each mesocosm of the fertilized treatment, we added 1000 µgL(-1) of KNO(3) and 200 µgL(-1) of KH(2)PO(4) during each sampling date. We found a relative high number of ciliate species (85 species) and a predominance of hypotrichs. Among the recorded species, about 25% occurred exclusively in the fertilized treatment. Moreover, detrended correspondence analysis demonstrated that the ciliate community associated with E. crassipes roots changed significantly in response to the nutrient input in such a way that the species composition of the fertilized treatment was remarkably different from that of the control. In contrast to our expectations, species richness in the fertilized treatment was significantly higher than that in the control, refuting our hypothesis that species richness decreases under eutrophic conditions.

Biodiversity of testate amoebae (Arcellinida and Euglyphida) in different habitats of a lake in the Upper Paraná River floodplain.

This study aimed to investigate the testate amoebae (Arcellinida and Eugliphida) species diversity in plankton, macrophytes and aquatic sediment samples from a shallow lake of the Upper Paraná River floodplain. Samples were carried out from April 2007 to March 2008. We recorded 89 taxa, belonging to 10 families. Eighty-two taxa were found in the aquatic sediment, 71 in the macrophytes and 53 in the plankton. Highest values of alpha diversity were observed in the aquatic sediment. Although the plankton had the highest number of accidental species, accessory and constant species were also observed in this habitat. Most of the species classified as constant for the plankton belonged to the genus Arcella. Most of the constant species in the macrophytes and aquatic sediment belonged to the genus Difflugia. This study supports the idea that the presence of these protists in the plankton should not be attributed only to stochastic processes because (i) the species diversity recorded in this habitat was remarkably high in relation to the total biodiversity of the lake, and (ii) we also recorded frequent and constant species in the plankton.

Composition and species richness of flagellate protozoa from environments associated to the Baía river (Mato Grosso do Sul State, Brazil): influence of the hydrological period and the connectivity / Composição e riqueza de espécies de protozoários flagelados de ambientes associados ao rio Baía (Mato Grosso do Sul, Brasil): influência do período hidrológico e da conectividade

Despite flagellate protozoa are important for the metabolism of aquatic ecosystems, researches about the ecology of this community is scarce. Therefore, this study investigated the influence of flood regime and hydrological connectivity on the patterns of composition and species richness of protozoan flagellates from aquatic environments in the upper Paraná river floodplain. To this end, samplings were undertaken in two periods of the hydrological cycle (March 2008 and September 2008), at six lentic environments associated with the Baía river (three are connected to the river, and three are isolated). 120 taxa were identified in the studied area, distributed in 10 orders and one residual group. This high species richness was sustained by the order Euglenida, which contributed with 70% of total species. The species composition was significantly different between periods and environments, as well as species richness, which was higher in connected environments during the high water period. The results evidenced that the flood pulse and hydrological connectivity are relevant factors driving the structure and dynamic of plankton flagellate protozoa community in the upper Paraná river floodplain.

Apesar dos protozoários flagelados serem importantes para o metabolismo dos ecossistemas aquáticos, os estudos sobre a ecologia desta comunidade são escassos. Nesse contexto, este estudo tem por objetivos investigar a influência do regime de inundação e da conectividade hidrológica sobre os padrões de composição e riqueza de espécies de protozoários flagelados da planície de inundação do alto rio Paraná. Para tal, foram realizadas coletas em dois períodos do ciclo hidrológico (março/2008 e setembro/2008), em seis ambientes lênticos associados ao rio Baia (sendo três conectados ao rio e três desconectados). Foram identificados 120 táxons na área de estudo, distribuídos em 10 ordens e um grupo residual. Essa elevada riqueza de espécies foi sustentada pela ordem Euglenida, que contribuiu com 70% do total das espécies registradas. A composição de espécies foi significativamente diferente entre os períodos e entre os ambientes, assim como a riqueza de espécies, que foi maior nos ambientes conectados e durante o período de águas altas. Esses resultados demonstraram que o regime de inundação e a conectividade hidrológica são fatores relevantes na estruturação e na dinâmica da comunidade de protozoários flagelados planctônicos, na planície de inundação do alto rio Paraná.

Proteocephalidean larvae (Cestoda) in naturally infected cyclopid copepods of the upper Paran River floodplain, Brazil.

The occurrence, prevalence and infection intensity of proteocephalidean larvae in naturally infected intermediate hosts of the Upper Paran River floodplain are reported. A total of 5,206 zooplanktonic and benthic organisms were analyzed, namely cyclopid (2,621) and calanoid (1,479) copepods, cladocerans (704), rotifers (307), chironomid larvae (41) and ostracods (54). Eight cyclopid copepods - two copepodids, one male and five females - comprising 0.3% of the cyclopid copepods examined, were naturally infected. The male infected belonged to a species of Paracyclops, and the females to Paracyclops sp., Thermocyclops minutus and Mesocyclops longisetus.

Proteocephalidean larvae (Cestoda) in naturally infected cyclopid copepods of the upper Paraná River floodplain, Brazil

The occurrence, prevalence and infection intensity of proteocephalidean larvae in naturally infected intermediate hosts of the Upper Paraná River floodplain are reported. A total of 5,206 zooplanktonic and benthic organisms were analyzed, namely cyclopid (2,621) and calanoid (1,479) copepods, cladocerans (704), rotifers (307), chironomid larvae (41) and ostracods (54). Eight cyclopid copepods - two copepodids, one male and five females - comprising 0.3 percent of the cyclopid copepods examined, were naturally infected. The male infected belonged to a species of Paracyclops, and the females to Paracyclops sp., Thermocyclops minutus and Mesocyclops longisetus