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Periphyton communities in freshwater systems play an essential role in biogeochemical processes, but knowledge of their structure and dynamics lags far behind other environments. We used eDNA metabarcoding of 16S and 18S rRNA markers to investigate the formation and establishment of a periphytic community, in addition to a morphology-based approach for peritrich ciliate determinations, its most abundant group. We sampled two nearby sites within a large Neotropical lake at four time points, aiming to assess whether periphyton establishment can be replicated on this local scale. Producers and denitrifiers were abundant in the community, illustrating the relevant role of biofilms in freshwater nutrient recycling. Among microeukaryotes, peritrich ciliates dominated the community, with genera Epistylis and Vorticella being the most abundant and showing a clear succession at both sites. Other ciliates were morphologically identified and, in some cases, their occurrence was strongly related to bacterial abundance. The structure of both prokaryotic and eukaryotic components of periphyton was not different, while the turnover dynamics differed between the two sites, in spite of their adjacent locations and similar abiotic properties. This indicates that the establishment of these communities can vary even on a local scale within a lake ecosystem.

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Temporary waters are common environments found in physical and biological substrates. Among them, some bromeliads species are known to hold water in their tanks, in a habitat called phytotelmata. Phytotelmata serve as habitats for several organisms, from bacteria and protists to arthropods and anurans. Peritrich ciliates are often found as epibionts on aquatic invertebrates in these environments. Here, we report two cases of epibiosis involving Lagenophrys sp. attached to ostracods (Elpidium spp.) and Rhabdostyla sp. colonizing hydrachnid mites in the tanks of two bromeliad species. In our analysis, we measured the frequency of epibiosis considering the presence of both basibiont and epibiont in the samples. The results shown a significant difference between Elpidium sp. and Lagenophrys sp. compared to hydrachnid mites and Rhabdostyla sp. (87.5% and 19%, respectively), supported by the Kruskal-Walis test (p = 0.0003, Chi-square = 9.687). These reports are important since the knowledge of phytotelmata communities from tropical and subtropical areas is incipient, although it has been increasing over the last years. It also shows that epibiosis doesn't always represent a beneficial relationship. These two epibiosis systems found in bromeliad tanks raise questions about organism's dispersal throughout other phytotelmata and other temporary water habitats.

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To investigate patterns of biotic community composition at different spatial scales and biological contexts, we used environmental DNA metabarcoding to characterize eukaryotic and prokaryotic assemblages present in the phytotelmata of three bromeliad species (Aechmea gamosepala, Vriesea friburgensis, and Vriesea platynema) at a single Atlantic Forest site in southern Brazil. We sampled multiple individuals per species and multiple tanks from each individual, totalizing 30 samples. We observed very high levels of diversity in these communities, and remarkable variation across individuals and even among tanks from the same individual. The alpha diversity was higher for prokaryotes than eukaryotes, especially for A. gamosepala and V. platynema samples. Some biotic components appeared to be species-specific, while most of the biota was shared among species, but varied substantially in frequency among samples. Interestingly, V. friburgensis communities (which were sampled at nearby locations) tended to be more heterogeneous across samples, for both eukaryotes and prokaryotes. The opposite was true for V. platynema, whose samples were more broadly spaced but whose communities were more similar to each other. Our results indicate that additional attention should be devoted to within-individual heterogeneity when assessing bromeliad phytotelmata biodiversity, and highlight the complexity of the biotic assemblages gathered in these unique habitats.

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In Argentina, Saccocoelioides bacilliformis Szidat, 1973 was described from specimens collected probably in Astyanax bimaculatus (Linnaeus, 1758), but latter it was synonymyzed with Saccocoelioides octavus Szidat, 1970. During the examination of digenetic trematodes collected in different species of Astyanax Baird & Girard, 1854 from southern Brazil, we found specimens identified as Saccocoelioides. A detailed comparison of the morphology of the two species revealed that they should be considered valid, thus this study proposes the revalidation of S. bacilliformis. The traits that allowed the revalidation were: body shape, position of the caecal bifurcation, and the extension of the uterus and vitellarium. Parameters of infections are provided for the first time in addition to records of new hosts and new locality.

Na Argentina, Saccocoelioides bacilliformis Szidat, 1973 foi descrita a partir de espécimes coletados provavelmente de Astyanax bimaculatus (Linnaeus, 1758), mas posteriormente foi sinonimizada com Saccocoelioides octavus Szidat, 1970. Durante o exame de trematódeos digenéticos coletados de diferentes espécies de Astyanax Baird & Girard, 1854 no sul do Brasil, foram encontrados espécimes identificados como Saccocoelioides. Uma comparação detalhada da morfologia das duas espécies revelou que elas devem ser consideradas válidas, portanto este estudo propõe a revalidação de S. bacilliformis. Os caracteres morfológicos que permitiram a revalidação foram: formato do corpo, posição da bifurcação cecal e a extensão do útero e vitelário. Os parâmetros das infecções são fornecidos pela primeira vez, bem como o registro de novos hospedeiros e de uma nova localidade.

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ABSTRACT In Argentina, Saccocoelioides bacilliformis Szidat, 1973 was described from specimens collected probably in Astyanax bimaculatus (Linnaeus, 1758), but latter it was synonymyzed with Saccocoelioides octavus Szidat, 1970. During the examination of digenetic trematodes collected in different species of Astyanax Baird & Girard, 1854 from southern Brazil, we found specimens identified as Saccocoelioides. A detailed comparison of the morphology of the two species revealed that they should be considered valid, thus this study proposes the revalidation of S. bacilliformis. The traits that allowed the revalidation were: body shape, position of the caecal bifurcation, and the extension of the uterus and vitellarium. Parameters of infections are provided for the first time in addition to records of new hosts and new locality.

RESUMO Na Argentina, Saccocoelioides bacilliformis Szidat, 1973 foi descrita a partir de espécimes coletados provavelmente de Astyanax bimaculatus (Linnaeus, 1758), mas posteriormente foi sinonimizada com Saccocoelioides octavus Szidat, 1970. Durante o exame de trematódeos digenéticos coletados de diferentes espécies de Astyanax Baird & Girard, 1854 no sul do Brasil, foram encontrados espécimes identificados como Saccocoelioides. Uma comparação detalhada da morfologia das duas espécies revelou que elas devem ser consideradas válidas, portanto este estudo propõe a revalidação de S. bacilliformis. Os caracteres morfológicos que permitiram a revalidação foram: formato do corpo, posição da bifurcação cecal e a extensão do útero e vitelário. Os parâmetros das infecções são fornecidos pela primeira vez, bem como o registro de novos hospedeiros e de uma nova localidade.

RESUMO

In Argentina, Saccocoelioides bacilliformis Szidat, 1973 was described from specimens collected probably in Astyanax bimaculatus (Linnaeus, 1758), but latter it was synonymyzed with Saccocoelioides octavus Szidat, 1970. During the examination of digenetic trematodes collected in different species of Astyanax Baird & Girard, 1854 from southern Brazil, we found specimens identified as Saccocoelioides. A detailed comparison of the morphology of the two species revealed that they should be considered valid, thus this study proposes the revalidation of S. bacilliformis. The traits that allowed the revalidation were: body shape, position of the caecal bifurcation, and the extension of the uterus and vitellarium. Parameters of infections are provided for the first time in addition to records of new hosts and new locality.(AU)

Na Argentina, Saccocoelioides bacilliformis Szidat, 1973 foi descrita a partir de espécimes coletados provavelmente de Astyanax bimaculatus (Linnaeus, 1758), mas posteriormente foi sinonimizada com Saccocoelioides octavus Szidat, 1970. Durante o exame de trematódeos digenéticos coletados de diferentes espécies de Astyanax Baird & Girard, 1854 no sul do Brasil, foram encontrados espécimes identificados como Saccocoelioides. Uma comparação detalhada da morfologia das duas espécies revelou que elas devem ser consideradas válidas, portanto este estudo propõe a revalidação de S. bacilliformis. Os caracteres morfológicos que permitiram a revalidação foram: formato do corpo, posição da bifurcação cecal e a extensão do útero e vitelário. Os parâmetros das infecções são fornecidos pela primeira vez, bem como o registro de novos hospedeiros e de uma nova localidade.(AU)

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Abstract: The acanthocephalan species Quadrigyrus torquatus Van Cleave, 1920 has been found in different hosts from South America, but recent papers have not focused on its morphology traits. Different species of Astyanax Baird & Girard, 1854 were collected with seine nets between January 2017 and October 2017 in Pintada Island, Lake Guaíba, Porto Alegre city (30º17'11''S and 51º18'01"W), Rio Grande do Sul State, Brazil. Acanthocephalans found in cysts were processed according to the techniques for the group. Specimens of Q. torquatus were identified based mainly in the morphology of proboscis hooks and trunk spines, and by the measurements made using light microscopy. Supplemental observations on the morphology of Q. torquatus were made for the first time considering the morphology and amount of hooks and spines. The amplitude of intensity of infections was 1 (A. aff. fasciatus) and 1‒3 (A. lacustris) helminths. This difference could be related to the number of hosts examined, the feeding habit of the hosts or related to aspects in the parasite life cycle. This paper is the first report of Q. torquatus in A. aff. fasciatus and A. lacustris from Lake Guaíba, extending the distribution to the southernmost state of Brazil, thus contributing to the knowledge of acanthocephalans in freshwater fishes from South America.

Resumo: A espécie de acantocéfalo Quadrigyrus torquatus Van Cleave, 1920, tem sido encontrada em diferentes hospedeiros na América do Sul, contudo os estudos recentes não focam no estudo dos caracteres morfológicos. Diferentes espécies de Astyanax Baird & Girard, 1854 foram coletadas com redes do tipo picaré entre janeiro e outubro de 2017, na Ilha da Pintada, Lago Guaíba, Cidade de Porto Alegre (30º17'11''S e 51º18'01"W), Estado do Rio Grande do Sul, Brasil. Os acantocéfalos encontrados encistados foram processados de acordo com as técnicas para o grupo. Os espécimes de Q. torquatus foram identificados principalmente pela morfologia dos ganchos da probóscide, espinhos do tronco e, pelas medidas realizadas através de microscopia de luz. Observações suplementares na morfologia de Q. torquatus foram realizadas pela primeira vez, considerando a morfologia e o número de ganchos e espinhos. A amplitude das infecções foi 1 (A. aff. fasciatus) e 1‒3 (A. lacustris) helmintos. Esta diferença pode estar associada com o número de hospedeiros examinados, com os hábitos alimentares dos hospedeiros, ou relacionada com aspectos no ciclo de vida do parasito. Este estudo é o primeiro registro de Q. torquatus em A. aff. fasciatus e A. lacustris do Lago Guaíba, estendendo a distribuição do parasito para o sul do Brasil, contribuindo com o conhecimento dos acantocéfalos parasitos de peixes de água doce na América do Sul.

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The peritrich ciliates Vorticella veloxiiforme n.sp. and Vorticella ampullaria n.sp. were found as epibionts on the ampullarid mollusk Pomacea canaliculata collected from Patos Lagoon, Rio Grande do Sul state, Brazil. The detailed morphology of both species was investigated using live and stained specimens, as well as scanning electron microscopy. Zooids of Vorticella veloxiiforme are cup shaped measuring 57 X 41 µm on average. A J-shaped macronucleus lies in the upper half of the cell. One contractile vacuole was observed in the upper part of the cell. V. ampullaria presents an elongate zooid measuring 70 X 25 µm on average. A C-shaped macronucleus lies in the middle of the cell. Two contractile vacuoles are present: one close to the peristome and the other in the lower half of the cell. The pattern of oral polykinetids was typical of the genus, with all infundibular polykinetids composed by three rows of kinetosomes each. SEM revealed a regular pattern of pores present on the zooid membrane of both species. Analyses of the 18s rDNA placed the two new species in the order Vorticellida close to described species of Vorticella.

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Bromeliads are a diverse group of plants that includes many species whose individuals are capable of retaining water, forming habitats called phytotelmata. These habitats harbor a diversity of organisms including prokaryotes, unicellular eukaryotes, metazoans, and fungi. Among single-celled eukaryotic organisms, ciliates are generally the most abundant. In the present study, we used Illumina DNA sequencing to survey the eukaryotic communities, especially ciliates, inhabiting the tanks of the bromeliads Aechmea gamosepala and Vriesea platynema in the Atlantic Forest of southern Brazil. Filtered sequences were clustered into distinct OTUs using a 99% identity threshold, and then assigned to phylum and genus using a BLAST-based approach (implemented in QIIME) and the SILVA reference database. Both bromeliad species harbored very diverse eukaryotic communities, with Arthropoda and Ciliophora showing the highest abundance (as estimated by the number of sequence reads). The ciliate genus Tetrahymena was the most abundant among single-celled organisms, followed by apicomplexan gregarines and the ciliate genus Glaucoma. Another interesting finding was the presence and high abundance of Trypanosoma in these bromeliad tanks, demonstrating their occurrence in this type of environment. The results presented here demonstrate a hidden diversity of eukaryotes in bromeliad tank waters, opening up new avenues for their in-depth characterization.

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The peritrich ciliate Epistylis portoalegrensis n. sp. was found in two bodies of freshwater located in Porto Alegre, Southern Brazil. Morphological features were investigated using live and protargol-stained specimens. The zooids presented a vase to cylindrical shape narrowed at the scopula, and a mean size of 131 × 37 µm in vivo. A C-shaped macronucleus lay in the middle of the cell close to a single contractile vacuole. The oral infraciliature was typical for the genus, with all infundibular polykineties composed by three distinct rows of kinetosomes. Colonies are often nonbranched with no lateral stalk, carrying several zooids stemming from a single point. Specimens from the two sampling sites showed identical arrangement of the infraciliature, similar morphometry, identical 18S rDNA sequences, and a single nucleotide difference across the more variable ITS regions. Molecular phylogenetic analyses placed E. portoalegrensis in a well-supported clade containing other Epistylis species, within the order Vorticellida.

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Epistylis smalli n. sp., a freshwater colonial peritrich, was collected in Guaíba Lake, Southern Brazil. Its morphology was investigated using in vivo observations and protargol stained specimens. E. smalli possess an elongate zooid that measures in vivo, on average, 173 µm in length and 50 µm in width. A C-shaped macronucleus that surrounds the infundibulum and a single contractile vacuole could be easily observed in the living cell. The oral infraciliature observed in silver-stained specimens was typical of peritrich ciliates, with three infundibular polykinetids bearing three rows of kinetosomes. A detailed description of the live and stained zooids is given.

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This study evaluated the influence of rainfall amount on the abundance, species richness, and species occurrence and abundance distribution of the ciliate community associated with the bromeliad Aechmea distichantha. The plants were collected from a rock wall of about 10-km long at the left bank of Paraná River. We assessed the effects of both spatial and temporal variables on the community attributes, as well as whether plants geographically closer have a similar abundance distribution and species composition. The ciliate community was substantially distinct between both hydrological periods, with greater values of species richness and abundance in the rainy period. No spatial structuring (differences in the species occurrence and abundance distribution among strata) or geographical similarity (similarity in ciliate species composition among the plants) was found. Multiple regression analysis showed a positive relationship only between the ciliate abundances and water volumes for both periods. Although few of the formulated predictions were confirmed, our study provides valuable information on the ecological aspects of the ciliate community inhabiting bromeliad phytotelmata.

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Epistylis riograndensis n. sp., a freshwater peritrich hosting symbiotic algae in its cytoplasm, was collected from an artificial lake, in a Botanical garden in Southern Brazil. Its detailed morphology was investigated using live and silver-stained specimens. The colonial sessile E. riograndensis has elongate zooids measuring, on average, 162 µm in length and 45 µm in width. A single contractile vacuole located near the infundibulum and a C-shaped macronucleus located transversely in the adoral half of the cell were also observed. The oral infraciliature revealed in silver-stained specimens was typical of peritrich ciliates. Three infundibular polykineties consisting of 3 rows of kinetosomes were observed. Molecular analyses of 18s rDNA placed E. riograndensis among other Epistylis species in the Order Vorticellida.

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Phytotelmata are vegetal structures that hold water from the rain, and organic matter from the forest and the soil, resulting in small, compartmentalized bodies of water, which provide an essential environment for the establishment and development of many organisms. These microenvironments generally harbor endemic species, but many organisms that are found in lakes and rivers, are also present. Here, we report, for the first time, the occurrence of the ciliate genus Paramecium in the tank of the bromeliad species Aechmaea distichantha. The identification of the Paramecium species was performed based on live observations, protargol impregnation, scanning electronic microscopy, and sequencing of the 18s rRNA. The absence of Paramecium from bromeliad tank water was highlighted in several earlier investigations, and may be due to the fact that this species is unable to make cysts. The occurrence of Paramecium multimicronucleatum in our samples may be explained by the proximity between the bromeliads and the river, a potential source of the species. Further, we also believe that the counting methodology used in our study provides a more accurate analysis of the species diversity, since we investigated all samples within a maximum period of 6 h after sampling, allowing minimum loss of specimens.

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We have generated 18S rRNA sequences for peritrichs collected in Brazil, including four Opercularia species, two different populations of Epistylis plicatilis (one epibiont and another free-living), and one additional Epistylis species. Our Opercularia species clustered with the previously available Opercularia microdiscum, corroborating the monophyly of this genus. The Epistylis sampled here clustered with previously sequenced species of this genus. The two populations of E. plicatilis collected in Brazil clustered closely together despite their different ecological contexts, whereas both were very divergent from the sample assigned to the same species previously sampled in China. If affirmed by additional morphological corroboration of species assignment, this observation would indicate that samples from different continents morphologically allocated in the same species may in fact belong to distant evolutionary lineages. More broadly, our results support the recognition of two major clades within Peritrichia. Given the robustness of their support, we suggest that these two clades should be formally recognized as orders, and propose the names Vorticellida and Operculariida to designate them. Furthermore, Epistylis species occurred in both orders, tending to occupy basal positions. This suggests that characters used to define this genus may be plesiomorphic for Peritrichia, so that Epistylis may in fact represent an assemblage of basal species retaining ancestral features.

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Phylogenetic relationships among peritrich ciliates remain unclear in spite of recent progress. To expand the analyses performed in previous studies, and to statistically test hypotheses of monophyly, we analyzed a broad sample of 18s rRNA sequences (including 15 peritrich genera), applying a conservative alignment strategy and several phylogenetic approaches. The main results are that: (i) the monophyly of Peritrichia cannot be rejected; (ii) the two main clades of Sessilida do not correspond to formally recognized taxa; (iii) the monophyly of genera Vorticella and Epistylis is significantly rejected; and (iv) morphological structures commonly used in peritrich taxonomy may be evolutionarily labile.

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