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BACKGROUND: The backbone of the eukaryotic tree of life contains taxa only found in molecular surveys, of which we still have a limited understanding. Such is the case of Picozoa, an enigmatic lineage of heterotrophic picoeukaryotes within the supergroup Archaeplastida, which has emerged as a significant component of marine microbial planktonic communities. To enhance our understanding of the diversity, distribution, and ecology of Picozoa, we conduct a comprehensive assessment at different levels, from assemblages to taxa, employing phylogenetic analysis, species distribution modeling, and ecological niche characterization. RESULTS: Picozoa was among the ten most abundant eukaryotic groups, found almost exclusively in marine environments. The phylum was represented by 179 Picozoa's OTU (pOTUs) placed in five phylogenetic clades. Picozoa community structure had a clear latitudinal pattern, with polar assemblages tending to cluster separately from non-polar ones. Based on the abundance and occupancy pattern, the pOTUs were classified into four categories: Low-abundant, Widespread, Polar, and Non-polar. We calculated the ecological niche of each of these categories. Notably, pOTUs sharing similar ecological niches were not closely related species, indicating a phylogenetic overdispersion in Picozoa communities. This could be attributed to competitive exclusion and the strong influence of the seasonal amplitude of variations in environmental factors, such as temperature, shaping physiological and ecological traits. CONCLUSIONS: Overall, this work advances our understanding of uncharted protists' evolutionary dynamics and ecological strategies. Our results highlight the importance of understanding the species-level ecology of marine heteroflagellates like Picozoa. The observed phylogenetic overdispersion challenges the concept of phylogenetic niche conservatism in protist communities, suggesting that closely related species do not necessarily share similar ecological niches. Video Abstract.

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Over two decades, the area with sugarcane has more than doubled, from 4.8 million hectares in 2000 to 10 million in 2018, in Brazil. São Paulo State is mostly responsible for the sugarcane production in the country, accounting for 51% of the national production. In 2008, a study was conducted analysing the relationship between sugarcane cultivation and the aquatic macroinvertebrate community, showing the impacts of sugarcane on the macroinvertebrate aquatic fauna. The present study aims to gather actual information on the aquatic macroinvertebrate community in the same streams studied in 2008, to make a historical comparison with studies previously carried out. Eight streams were selected; four located in areas of sugarcane cultivation and four located in preserved areas. Three samples were carried out between 2018 and 2020. The aquatic macroinvertebrates were collected using a D-frame aquatic net (250 µm) including riffle and pools areas and identified using specific identification keys. The results of the historical assessment showed better ecological conditions of the streams in 2008 when compared to 2018 in areas of sugarcane cultivation, suggesting that the environmental impact was maintained and increased after ten years.

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Recent progress in understanding the early evolution of eukaryotes was tied to morphological identification of flagellates and heliozoans from natural samples, isolation of their culture and genomic and ultrastructural investigations. These protists are the smallest and least studied microbial eukaryotes but play an important role in the functioning of microbial food webs. Using light and electron microscopy, we have studied the diversity of heterotrophic flagellates and centrohelid heliozoans from marine waters of Curacao (The Netherlands Antilles), and provide micrographs and morphological descriptions of observed species. Among 86 flagellates and 3 centrohelids encountered in this survey, five heterotrophic flagellates and one сentrohelid heliozoan were not identified even to the genus. Some flagellate protists have a unique morphology, and may represent undescribed lineages of eukaryotes of high taxonomic rank. The vast majority (89%) of identified flagellates is characterized by wide geographical distribution and have been reported previously from all hemispheres and various climatic regions. More than half of the species were previously observed not only from marine, but also from freshwater habitats. The parameters of the species accumulation curve indicate that our species list obtained for the Curacao study sites is far from complete, and each new sample should yield new species.

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The Southeast Pacific comprises two Large Marine Ecosystems, the Pacific Central-American Coastal and the Humboldt Current System; and is one of the less well known in the tropical subregions in terms of biodiversity. To address this, we compared DNA barcoding repositories with the marine biodiversity species for the Southeast Pacific. We obtained a checklist of marine species in the Southeast Pacific (i.e. Colombia, Ecuador, Chile, and Peru) from the Ocean Biodiversity Information System (OBIS) database and compared it with species available at the Barcoding of Life Data System (BOLD) repository. Of the 5504 species records retrieved from OBIS, 42% of them had at least one registered specimen in BOLD (including specimens around the world); however, only 4.5% of records corresponded to publicly available DNA barcodes including specimens collected from a Southeast Pacific country. The low representation of barcoded species does not vary much across the different taxonomic groups or within countries, but we observed an asymmetric distribution of DNA barcoding records for taxonomic groups along the coast, being more abundant for the Humboldt Current System than the Pacific Central-American Coastal. We observed high-level of barcode records with Barcode Index Number (BIN) incongruences, particularly for fishes (Actinopterygii = 30.27% and Elasmobranchii = 24.71%), reflecting taxonomic uncertainties for fishes, whereas for Invertebrates and Mammalia more than 85% of records were classified as data deficient or inadequate procedure for DNA barcoding. DNA barcoding is a powerful tool to study biodiversity, with a great potential to increase the knowledge of the Southeast Pacific marine biodiversity. Our results highlight the critical need for increasing taxonomic sampling effort, the number of trained taxonomic specialists, laboratory facilities, scientific collections, and genetic reference libraries.

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In the present study, we analyzed a unique phytophysiognomy in the Amazon region, which is formed by savanna-like vegetation on iron-rich soil (known locally as canga) located within an iron-ore mining region. We used the habitat template theory to test the hypothesis that changes in the physical-chemical properties of streams and the physical structure of their habitats at in-stream and micro-basin (landscape) levels affect the taxonomic and trophic composition of immature aquatic insects. For this, we used a local environmental matrix composed of nine physical-chemical and structural habitat variables, together with the Habitat Integrity Index. We also calculated landscape metrics based on the area of the micro-basin, such as relief, slope, mean current flow, and vegetation cover. We divided the aquatic insects into five functional feeding groups based on their diet and food sources. Our results indicate that changes in the trophic level of the insects of the orders Ephemeroptera, Plecoptera, and Trichoptera are more easily observed than the taxonomic structure of communities. The loss of environmental integrity and vegetation cover were responsible for 84% of the variation observed in the composition of functional feeding groups (FFGs). Our study shows that aquatic insect communities in the canga and in the Amazon regions dominated by forest require specific in-stream and landscape conditions. These findings reinforce the need for the preservation of areas of canga vegetation, which not only have a unique levels of biological diversity, but are also targeted for the exploitation of their economically valuable natural resources.

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The present study describes the community diversity and gives a seasonal distribution of an intertidal macroalgal assemblage at Prainha Beach, Arraial do Cabo City in Rio de Janeiro state, Brazil. Sampling was performed during four seasons of a 1-year period. Organisms were sampled and photographed using photoquadrats to quantify relative coverage. Ninety-six taxa of macroalgae were registered, including 23 chlorophytes, 19 ochrophytes, and 54 rhodophytes, while three barnacles, seven mollusks, one isopod, and one polychaete were recorded among the zoobenthos. In the upper intertidal zone, the coverage was frequently dominated by invertebrates. Macroalgae always dominated the middle and lower zones, covering almost 100 % in both zones. The highest values of species diversity (H'), richness (S), and turnover rates were found during the transition from spring to summer, which coincided with the upwelling period. A comparison with the 1980's flora revealed that the major changes in the macroalgal assemblage were among species belonging to the same genera, unless new additions were provided. The combination of photoquadrats and minimally destructive sampling allowed a detailed description of the composition and structural characteristics of the intertidal zone, a methodology that should be applied to study protected marine areas.

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Several countries included the assessment of environmental drift contamination risk for the registration of pesticides. This practice is not yet totality effective in Brazil; however, due to the large number of pesticides in use, it is important to identify the real contamination risk during pesticide spraying. Therefore, this study determined the indices of environmental risks for exposure to drift from terrestrial applications of fungicides, herbicides, and insecticides that are used in soybean crops under Brazilian climate conditions and established buffer zones for the application of these products. Based on the three prediction drift models for soybeans in Brazil, risk indices were computed for aquatic organisms and terrestrial organisms according to the modelling procedures proposed by the POCER (Pesticide Occupation and Environmental Risk) and HAIR (Harmonized Environmental Indicators for Pesticide Risk) methodologies. In general, aquatic organisms are the most sensitive to drift contamination, being chlorothalonil, trifluralin and chlorpyrifos the ones that presented the higher risk indexes. No risk was found for earthworms; in contrast, the insecticides chlorpyrifos, spinosad and thiamethoxam presented risks to bees regardless of the nozzle (droplet size) used for the determination of the drift curve, resulting in the demand for different buffer zones.

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Human occupation of coastal areas promotes the establishment of non-native species but information on bioinvasions is usually biased toward the Northern Hemisphere. We assessed non-native species' importance in sessile communities at six marinas along the most urbanized area of the Southwestern Atlantic coastline. We found 67 species, of which 19 are exotic. The most frequent species was the exotic polychaete Branchiomma luctuosum, while the most abundant was the exotic bryozoan Schizoporella errata that monopolized the substrata in three marinas. Along with S. errata, the exotic polychaete Hydroides elegans and ascidian Styela plicata dominated space in the three remaining marinas, while native species were in general rare. We show that communities associated with artificial substrata along this Brazilian urbanized area are dominated by exotic species and that using abundance data along with species identity can improve our understanding of the importance of exotic species for the dynamics of biological communities.

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Pollution of rivers and streams, by anthropic action, is characterized as an environmental, social, and sanitary problem. Factors such as the association between the marginal vegetation, the distribution of the substrates in the riverbed, and the availability of allochthonous organic matter influence the distribution and composition of the aquatic entomofauna. The objective of this study was to analyze the structure of aquatic insect communities in a pasture stream in northern Paraná, southern Brazil, with emphasis on the groups of indicators of good water quality, thus inferring the conditions of its preservation. Samples were collected from July to October in three parts of the stream (P1, P2, and P3), where the insect faune was collected with the aid of a sieve in the foliage substrate and washing of rocks and decomposing pieces of wood. A total of 1323 individuals were collected, being Chironomidae (Diptera) the most abundant taxon. The analysis of the biotic indices (EPT/Chironomidae, IBF, BMWP, and BMWP/ASPT) and diversity indicated better preservation conditions at points P1 and P3 where the riparian forest was well preserved, with less exposure to the stream bed. In P2, the entomofauna presented less diversity and the biotic indexes indicated loss of water quality, showing the impacts of changes in the marginal vegetation of this section. In a generally preserved aquatic environment, small changes in its vegetation are sufficient to cause an imbalance in the aquatic insect community, showing the efficiency of these organisms as bio-indicators and the sensitivity of biotic indexes.

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Macrodasyida (phylum Gastrotricha) comprises 365 species distributed across 34 genera and 10 families. However, current classification is under revision due to the contradictory results of molecular and morphological cladistic analyses. Studies aimed at bridging the gaps took advantage of supplementary assessments of poorly known species and particularly from observations of new taxa showing original traits that could help to identify plesiomorphic character states in these anatomically diverse micrometazoa. We follow this path by describing three new interesting macrodasyidan species respectively from Italy, Brazil and Sweden. In many respects, the new species resemble most closely species of the genus Macrodasys; however, details of the external morphology, in combination with the different lay-out of the reproductive system and the tiny spermatozoa lacking a visible flagellum, suggest they belong to a new genus, possibly in the family Macrodasyidae. These hypotheses are supported by the phylogenetic relationships of 47 taxa inferred from analyses of the 18S rRNA gene, which found the new species clustering with Thaidasys tongiorgii in a subset of a larger clade containing Macrodasys. Accordingly, the establishment of the following taxa is proposed: Kryptodasys gen. nov., K. marcocurinii sp. nov., K. carlosrochai sp. nov. and K. ulfjondeliusi sp. nov.

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Scientists are currently faced with the challenge of assessing the effects of anthropogenic stressors on aquatic ecosystems. Cellular stress response (CSR) biomarkers are ubiquitous and phylogenetically conserved among metazoans and have been successfully applied in environmental monitoring but they can also vary according to natural biotic and abiotic factors. The reported variability may thus limit the wide application of biomarkers in monitoring, imposing the need to identify variability levels in the field. Our aim was to carry out a comprehensive in situ assessment of the CSR (heat shock protein 70 kDa, ubiquitin, antioxidant enzymes) and oxidative damage (lipid peroxidation) in wild populations across marine taxa by collecting fish, crustaceans, mollusks and cnidarians during two different seasons (spring and summer) and two habitat types (coast and estuary). CSR end-point patterns were different between taxa with mollusks having higher biomarker levels, followed by the cnidarians, while fish and crustaceans showed lower biomarker levels. The PCA showed clear clusters related to mobility/sessile traits with sessile organisms showing greater levels (>2-fold) of CSR proteins and oxidative damage. Mean intraspecific variability in the CSR measured by the coefficient of variation (% CV) (including data from all seasons and sites) was elevated (35-94%). Overall, there was a seasonal differentiation in biomarker patterns across taxonomic groups, especially evident in fish and cnidarians. A differentiation in biomarker patterns between habitat types was also observed and associated with phenotypic plasticity or local adaptation. Overall, specimens collected in the estuary had lower biomarker levels when compared to specimens collected in the coast. This work highlights the importance of assessing baseline biomarker levels across taxa, seasons and habitats prior to applying biomarker analyses in environmental monitoring. Selecting bioindicator species, defining sampling strategies, and identifying confounding factors are crucial preliminary steps that ensure the success of biomarkers as powerful tools in biomonitoring.

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Pharmaceuticals are contaminants of emerging concern which have been a target of increasing attention by the scientific community. Pharmaceuticals presenting high consumption, incomplete metabolism and incomplete removal at wastewater treatment plants have been frequently detected in aquatic ecosystems worldwide. This is the case of the pharmaceuticals metformin (MET), bisoprolol (BIS), sotalol (SOT) and ranitidine (RAN). However, ecotoxicity data for these contaminants are scarce, especially regarding behavior effects and chronic toxicity. In addition, the knowledge regarding the joint toxicity of these pharmaceuticals on non-target organisms is still incipient, which makes their environment risk assessment uncertain. This study aimed to fill these knowledge gaps for these four pharmaceuticals, by carrying out toxicity tests using five test organisms from three trophic levels. Different endpoints were assessed in tests with Raphidocelis subcapitata (algae), Lemna minor (macrophyte), Daphnia similis (crustacean), Hydra attenuate (cnidarian) and Danio rerio (fish). The binary and quaternary mixture acute toxicity for these pharmaceuticals were assessed on D. similis and D. rerio embryo tests, respectively. This study also aimed to evaluate the predictive accuracy of the Concentration addition (CA) and the Independent action (IA) classic models. In addition, the nature of the possible toxicological interactions between the pharmaceuticals in binary mixtures were also evaluated, using the Combination Index-isobologram (CI) method. The modelling of the concentration-response curves and the associated statistical analyses were performed using the automated spreadsheet ToxCalcMix v.1.0 and the software OriginPro 2015. The software CompuSyn was used for performing the mixture analyses with the CI method. The experimental planning of the binary mixture tests was performed using the fractioned factorial design, in order to cover several possible ratio and level-dependent effects with a reduced number of test organisms. The results obtained in this study are shown in four articles. In article 1, we provided a critical review and discussed the misunderstandings, deficiencies and data gaps on the ecotoxicity data of pharmaceuticals and personal care products mixtures published in the literature. In the following articles, the results obtained from the single and mixture toxicity tests performed in this study were presented and discussed. The pharmaceuticals MET (article 2) and BIS (article 3) were classified as hazardous to the aquatic environment, in the acute toxicity category. However, an ecological risk is not expected for the pelagic freshwater species exposed to these two pharmaceuticals, based on the chronic data obtained. The results obtained from the mixture toxicity tests (article 4) showed that most of the observed toxicity effects from the binary mixtures were in the zone between the predicted effects by the CA and IA models. The CI model showed to be an useful tool to describe the possible toxicological interactions occurring between the pharmaceuticals in joint action. Even statistically significant non-effect concentrations of the pharmaceuticals added up to induce significant adverse effects in mixtures (something from nothing). It was concluded that ecological risk assessment based on single toxic effects can underestimate the real impact of environmental contaminants on aquatic ecosystems

A contaminação ambiental por fármacos tem sido alvo de crescente preocupação pela comunidade científica. Fármacos de elevado consumo, incompleto metabolismo e remoção incompleta em estações de tratamento de esgoto, como é o caso da metformina (MET), bisoprolol (BIS), sotalol (SOT) e ranitidina (RAN), têm sido frequentemente detectados em matrizes aquáticas do mundo todo. Apesar disso, dados ecotoxicológicos consistentes para esses contaminantes são escassos, principalmente com relação a efeitos comportamentais e oriundos de estudos crônicos. Além disso, o entendimento dos efeitos de suas ações combinadas em organismos não-alvo é ainda incipiente, o que gera incertezas na avaliação dos seus riscos ambientais. Esta pesquisa teve por objetivo preencher essas lacunas de conhecimentos para esses quatro fármacos, por meio da realização de testes com cinco diferentes organismos-teste de três diferentes níveis tróficos. Foram analisados diferentes parâmetros avaliativos em testes com os organismos aquáticos Raphidocelis subcapitata (alga), Lemna minor (macrófita), Daphnia similis (crustáceo), Hydra attenuata (cnidário) e Danio rerio (peixe). As toxicidades agudas das misturas binárias e quaternárias desses quatro fármacos também foram avaliadas em testes com D. similis e embriões de D. rerio, respectivamente. Este trabalho também teve por objetivo avaliar a acurácia preditiva dos modelos de adição de concentração (CA) e ação independente (IA) e analisar a natureza das possíveis interações toxicológicas entre os fármacos, em misturas binárias, usando o modelo do Índice de Combinação (CI). A modelagem das relações concentração-resposta e as análises estatísticas associadas foram realizadas empregando-se a planilha automatizada ToxCalcMix versão 1.0 e o software OriginPro 2015. O software CompuSyn foi utilizado para as análises envolvendo o CI. O planejamento experimental dos testes de misturas binárias foi realizado por meio do design fatorial fracionado, a fim de cobrir diversas possíveis interações em várias proporções e níveis de efeitos, com a redução do número de organismos-teste. Os resultados desta pesquisa estão apresentados em quatro artigos. No artigo 1, realizou-se uma revisão crítica com relação às lacunas de conhecimentos e deficiências identificadas a partir da análise da literatura sobre a ecotoxicologia de misturas de fármacos e de produtos de higiene pessoal. Nos artigos seguintes, foram apresentados e discutidos os resultados oriundos dos testes com os quatro fármacos avaliados neste estudo. Os fármacos MET (artigo 2) e BIS (artigo 3) foram classificados como perigosos para o ambiente aquático, na categoria de toxicidade aguda. Contudo, um risco ecológico não é esperado para as espécies pelágicas de água doce expostas a esses dois fármacos, com base nos dados de toxicidade crônica obtidos. Os resultados dos testes de misturas (artigo 4) permitiram concluir que a maior parte dos efeitos observados das misturas binárias estiveram na zona entre os efeitos preditos pelos modelos clássicos de CA e IA. O modelo do CI mostrou-se uma ferramenta útil para descrever a natureza das possíveis interações toxicológicas que ocorrem entre os fármacos em ações combinadas. Mesmo concentrações de nenhum efeito estatisticamente significativo dos fármacos causaram efeitos adversos significativos quando em misturas (something from nothing). Concluiu-se que avaliações de risco ecológicas baseadas em efeitos tóxicos individuais de contaminantes ambientais podem subestimar o real impacto desses compostos em ecossistemas aquáticos

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The biogeography of the Peruvian Eastern Pacific coast has been described based on oceanographic parameters and qualitative species occurrence data. This has generated disagreement about the limits and existence of different biogeographic units. In this study, the distribution of rocky-shore macrobenthic communities were recorded over 41 sites along the Peruvian coastline (3.5°S-13.5°S) and analyzed together with historic abiotic data in order to quantitatively evaluate the biogeographic zonation of rocky intertidal communities throughout the region and its relationship with environmental variables to propose an update bioregionalization. Clusters and non-metric multidimensional scaling were performed using Bray-Curtis dissimilarity matrices from abundance data to evaluate biogeographic patterns of dissimilarities of rocky-shore communities. Significant turnover of taxa among defined biogeographical units was tested using permutational multivariate dispersion. Relationships between of the biogeographical community's structure and environmental factors were examined using Random Forest analysis on datasets available at Bio-Oracle and Jet Propulsion Laboratory-California Institute of Technology. Variation of community structure of 239 taxa depicted three biogeographical units along the region matching Panamic, transitional and Humboldt provinces. Beta diversity analysis indicated a significant turnover of taxa within the transitional unit. Random forest analysis showed a strong correlation between biogeographic units with phosphate, sea surface temperature, nitrate, dissolved oxygen, cloud fraction, and silicates. Our results set the putative limits of three biogeographic units for rocky-shore communities along the coast of Peru, providing base-line information for understanding further biogeographic changes on communities associated with the ongoing regional coastal cooling and impacts of El Niño events.

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In lakes, the littoral habitat and its invertebrate communities are often exposed to water-level fluctuations. We examined the effects of seasonal changes on water level, substrata availability and benthic fauna in the littoral zone of Peri Lake, a shallow lake that has experienced a strong reduction in water level due to changes in rainfall. In this study, we also examined whether the abundance and composition of aquatic invertebrates differed among the four substrata. Our main objective was to assess the effect of seasonal changes on water level and benthic invertebrates inhabiting the different types of substrata. Benthic invertebrates were sampled four different substrata (Schoenoplectus californicus, sand and stones, allochthonous leaf litter, and macrophyte stands), and we also measured meteorological, physical and chemical variables. We found that complex habitats, such as allochthonous leaf litter and aquatic macrophyte, stand to be colonised by a larger number of macroinvertebrates because they provide more habitats or potential niches for colonisation by different species. In addition, we observed that during periods of low water level, the presence of substrata in the littoral zone decreased, as did the associated biota. Therefore, our results suggest that water level changes have a major functional impact on the littoral zone of the lake, and can affect substratum availability, which also impacts invertebrate communities.

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A identificação de espécies em alimentos é assunto de grande interesse para toda a cadeia de produção, para a fiscalização e para o meio acadêmico. Geralmente, o pescado é identificado com base nas características físicas de cada espécie. Porém, devido às limitações das análises morfológicas, as técnicas moleculares estão sendo cada vez mais empregadas para essa finalidade. A grande maioria destas utiliza a PCR para amplificar uma região de interesse do DNA de um material ou de um organismo, seguida da aplicação de métodos para a identificação da espécie. Os métodos mais utilizados são: eletroforese em gel, RFLP, PCR em tempo real, sequenciamento de DNA e DNA barcode, cada um com suas vantagens e aplicações específicas. As fraudes pela adição ou substituição de espécies em pescado ferem as legislações vigentes no Brasil e podem trazer graves consequências, incluindo perdas econômicas, desequilíbrios ambientais e riscos à saúde pública.

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A identificação de espécies em alimentos é assunto de grande interesse para toda a cadeia de produção, para a fiscalização e para o meio acadêmico. Geralmente, o pescado é identificado com base nas características físicas de cada espécie. Porém, devido às limitações das análises morfológicas, as técnicas moleculares estão sendo cada vez mais empregadas para essa finalidade. A grande maioria destas utiliza a PCR para amplificar uma região de interesse do DNA de um material ou de um organismo, seguida da aplicação de métodos para a identificação da espécie. Os métodos mais utilizados são: eletroforese em gel, RFLP, PCR em tempo real, sequenciamento de DNA e DNA barcode, cada um com suas vantagens e aplicações específicas. As fraudes pela adição ou substituição de espécies em pescado ferem as legislações vigentes no Brasil e podem trazer graves consequências, incluindo perdas econômicas, desequilíbrios ambientais e riscos à saúde pública.(AU)

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Marine meiofauna comprises up to 22 phyla. Its morphological identification requires time and taxonomists' expertise, and molecular tools can make this task faster. We aim to disentangle meiofaunal diversity patterns at Araçá Bay by applying a model selection approach and estimating the effectiveness of metabarcoding (18S rDNA) and morphological methods for estimating the response of meiofauna diversity in small-scale interactions with environmental variables. A rarefaction curve indicated that ten samples were sufficient for estimating the total number of meiofauna OTUs in a tidal flat. In both approaches, richness was predicted by mean sand percentage, sediment sorting, and bacteria concentration. Nematode genera composition differed significantly between approaches, the result of taxonomic mismatch in the genetic database. The similarity between the model selected for diversity descriptors, the richness of nematode genera and meiofauna composition emphasized the utility of predictive models for metabarcoding estimates to detect small-scale interactions of these organisms.

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For decades, microbial community composition in subseafloor sediments has been the focus of extensive studies. In deep lacustrine sediments, however, the taxonomic composition of microbial communities remains undercharacterized. Greater knowledge on microbial diversity in lacustrine sediments would improve our understanding of how environmental factors, and resulting selective pressures, shape subsurface biospheres in marine and freshwater sediments. Using high-throughput sequencing of 16S rRNA genes across high-resolution climate intervals covering the last 50 000 years in Laguna Potrok Aike, Argentina, we identified changes in microbial populations in response to both past environmental conditions and geochemical changes of the sediment during burial. Microbial communities in Holocene sediments were most diverse, reflecting a layering of taxa linked to electron acceptors availability. In deeper intervals, the data show that salinity, organic matter and the depositional conditions over the Last Glacial-interglacial cycle were all selective pressures in the deep lacustrine assemblage resulting in a genetically distinct biosphere from the surface dominated primarily by Bathyarchaeota and Atribacteria groups. However, similar to marine sediments, some dominant taxa in the shallow subsurface persisted into the subsurface as minor fraction of the community. The subsequent establishment of a deep subsurface community likely results from a combination of paleoenvironmental factors that have shaped the pool of available substrates, together with substrate depletion and/or reworking of organic matter with depth.

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Arene lychee sp. nov. is described from Canopus Bank, a seamount located ~190 km off Fortaleza, Ceará, NE Brazil (02°1425S, 38°2250W), based on shell morphology. The species is characterized by a large, trochiform shell; color ranging from intense reddish to white (darker on spiral cords, lighter at base) with a yellow apex; sculpture of 3-8 wide spiral cords with large scale-like spines; cords separated by deep interspaces with similar width, and interspaces sculptured by closely-packed, thin axial growth lines.

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Arene lychee sp. nov. is described from Canopus Bank, a seamount located ~190 km off Fortaleza, Ceará, NE Brazil (02°1425S, 38°2250W), based on shell morphology. The species is characterized by a large, trochiform shell; color ranging from intense reddish to white (darker on spiral cords, lighter at base) with a yellow apex; sculpture of 3-8 wide spiral cords with large scale-like spines; cords separated by deep interspaces with similar width, and interspaces sculptured by closely-packed, thin axial growth lines.(AU)

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