Abstract In the current research, edible meat of freshwater clam Corbicula fluminea was subjected to enzymatic peptide extraction using animal protease. The clam protein hydrolysate (CPH) contained 45.78% essential amino acids and 44.97% hydrophobic amino acids and showed high alcohol dehydrogenase (ADH) activation in vitro. Four fractions were divided from CPH by ultrafiltration and further investigated for their hepatoprotective effects on alcohol-induced injury in mice. The 2.5-5 kDa fraction (CPH-3) showed the best effect for preventing hepatic damage caused by alcohol, as revealed by reduced serum aspartate transaminase (AST) and alanine transaminase (ALT) activities and hepatic malondialdehyde (MDA) level, the marked decrease in the hepatic triglyceride (TG) contents, and the enhanced hepatic ADH, aldehyde dehydrogenase (ALDH), and glutathione (GSH) activities. Furthermore, histopathology of CPH-3-treated mice showed less hepatic tissue damage compared to alcohol- or other CPHs-treated mice. Hence, CPH-3 was further purified by consecutive chromatographic techniques with gel filtration and reverse-phase high-performance liquid chromatography. One hepatoprotective peptide, KKLAGFLRYYS (1330.68 Da), was identified by LC-MS/MS, which exhibited strong ADH activation activity. Results suggested that CPH could be a potential nutraceutical for facilitating alcohol metabolism and preventing or ameliorating early liver injury induced by acute alcohol exposure and that the peptide KKLAGFLRYYS is one of the main bioactive components in CPH.

Resumen La malacofauna de 9 sitios a lo largo de la cuenca río Sabinas, Coahuila, México, fue investigada con base en características conquiliológicas. En total, se encontraron 23 especies de moluscos dulceacuícolas, de las cuales 21 son nativas y 2 invasoras. Diecinueve especies son gasterópodos y 4 son bivalvos. Un género y 2 especies de gasterópodos intersticiales son endémicos del área y se reporta por primera vez a un miembro de la familia Amnicolidae en México, Lyogyrus sp. Mexithauma cf. quadripaludium Taylor, 1966, y Juturnia coahuilae (Taylor, 1966) (Cochliopidae), localizados únicamente en el valle de Cuatro Ciénegas, fueron encontrados por primera vez fuera del mismo. Además, también Cincinnatia integra (Say, 1821) (Hydrobiidae), conocida en México hasta la fecha solamente como relicto de un solo sitio en San Luis Potosí, fue encontrada viva en el río Sabinas. Las especies invasoras Melanoides tuberculata (O. F. Müller, 1774) (Thiaridae) y Corbicula fluminea (O. F. Müller, 1774) (Cyrenidae) dominan a las comunidades acuáticas de moluscos en todos los sitios estudiados. Estos dos moluscos forman un riesgo potencial para las especies nativas, especialmente si la contaminación del agua causada por actividades antropogénicas continúa. Por lo menos 10 especies del sistema río Sabinas son de especial importancia para la conservación (7 amenazadas y 3 vulnerables) debido a su endemismo, al hábitat reducido o a su presencia como relicto en México.

Abstract The malacofauna of the Sabinas River basin, Coahuila, North Mexico, was studied at 9 sites. In total, 21 native and 2 invasive species were found. Nineteen species were gastropods and 4 species were bivalves. One genus and 2 species of subterranean gastropods are endemic to the area. We report for the first time, a member of the family Amnicolidae in Mexico, Lyogyrus sp. Mexithauma cf. quadripaludium Taylor, 1966 and Juturnia coahuilae (Taylor, 1966) (Cochliopidae), previously known only as endemic in the neighboring Cuatro Ciénegas basin, were found for the first time outside of this basin. Also, Cincinnatia integra (Say, 1821) (Hydrobiidae), previously known in Mexico only from 1 relict site in San Luis Potosí state, was found living in Sabinas River. In all studied sites, the invasive species Melanoides tuberculata (O. F. Müller, 1774) (Thiaridae) and Corbicula fluminea (O. F. Müller, 1774) (Cyrenidae) dominate the aquatic molluscan communities. Both molluscs are potential risks for native species, especially if the water pollution continues. At least 10 species from Sabinas River System are of special conservation significance (7 imperiled and 3 vulnerable), due to their endemism, extremely reduced habitat, or relict occurrence in Mexico.

EXTENDED ABSTRACT A sedimentological study of the prograding area of the Paraná River delta (PRD) is here presented with the aim of characterizing the deposits related to the last ~100 yr. of paleoenvironmental evolution and to contribute to facies models of bayhead deltas. Delta deposits are the result of the interaction of various processes and factors (principally hydrological characteristics, waves, tidal action, type and volume of sedimentary discharge, water depth, sea level, climate) that disperse the sediments transported to the river mouth (Wright, 1977). The Paraná River, together with the contribution of the Uruguay River, develops a bayhead delta into the Río de la Plata (RdP) estuary (Fig. 1a). The delta constitutes an extensive plain with a very low gradient, lined by numerous fluvial channels of diverse hierarchy, and a series of distributary mouth bars with a lobate morphology (Figs. 1c, 2). It is a fluvial-dominated delta, regulated by the hydrological regime of its drainage basin and modulated by the estuary dynamics (Iriondo, 2004; Cavallotto et al., 2005). This bayhead delta has a drainage area of 3.000.000 km2. The Paraná river supplies 160 million tons of sediment per year to the delta mouth, with ~145 million tons of suspended sediments (30% clays, 60-65% silts and 5-10% sands) and 15 million tons of sands as bottom load (Sarubbiet al., 2004). In the Uruguay River, the suspended load reaches 7 million tons per year of sediments, with a higher contribution of sandy bottom sediments (Urien, 1972). Several studies revealed a high-constructive dynamic for the Paraná river delta during the last decades, with progradation rates of 30 to 70 m per year since AD 1818 (Soldano, 1947; Codignotto and Marcomini, 1993; Pittau et al., 2007; Leal, 2011; Medina and Codignotto, 2013). In particular, the study area grew an average of 42-45 m per year between AD 1933-2016 (Marcomini et al., 2018; Fig. 3). The PRD is placed at a temperate zone of southern South America, under a subhumid, mesothermal climate (periods 1981-1990 and 1991-2000; National Meteorological Service, 1992, 2003). Winds are mainly from the northeast and the southeast quadrants (Simionato and Vera, 2002), and are the main forcing of the RdP estuary circulation (Moreira et al., 2016). The estuary experiences a microtidal regime and the wave energy in the inner estuary is low (in average lower than 0.6 m high) and local (Moreira, 2016). Strong southeasterly wind (sudestada), that can last several days, triggers storm surges in the estuary and extensive floods in coastal areas (Seluchi, 1995). On the opposite, when ebb tides are accompanied by intense northeasterly winds, a very low water level happens (Simionato et al., 2004). Fitogeographically, the PRD belongs to the Neotropical region, and the vegetation is strongly influenced by the landscape and the hydrologic regime (Kandus et al., 2006). At the subaerial deltaic plain, plant communities are characterized by riparian forest along the levees and graminoid type plants in the interior, while bulrush colonizes the proximal subaqueous delta (Fig. 4d). Materials and methods include a geomorphologic-temporal evaluation, in-situ survey and sampling of surficial sediments and sediment cores in the lower subaerial and proximal subaqueous delta plains (34° 26’S, 58° 30’ W; Fig. 3), accompanied by lab determinations and then facies analysis. Surficial sediments were sampled with a Snapper dredge and the sediment cores were extracted using 2.5 inches PVC tubes. Grain size was measured with a Malvern Mastersizer Hydro 2000 laser analyzer, after pretreatment to eliminate organic content by soaking samples in hydrogen peroxide solution (H2O2) and rinsed with distilled water. The textural results were statistically processed and evaluated following the Folk and Ward (1957) protocols (Table 1). Due to the common presence of heterolithic sediments and in order to obtain an improved interpretation of the relationship between grain size distribution and sedimentary processes, extreme member (EM) analysis (after Paterson and Heslop, 2015) was applied to identify subpopulations (parametric curve-fitting applying the Weibull distribution; Fig. 5). EM modelling of the studied deposits was guided by geologic criteria and examined in terms of sediment availability and transport-deposition processes, including particle trapping due to bulrush vegetation (a common process in the PRD). The textural characterization by means of ME results a convenient technique to interpret mixed sediments like the here studied. Particularly, it can be useful when the sediment sample are acquired with dredges or augers, methods that produce the loss of sedimentary structures but demand less time and logistics than to extract cores. Sediment cores were described in terms of grain-size, sedimentary structures, color (Munsell, 2000), biological remains, mass magnetic susceptibility (SM, using a Bartington MS2B sensor) and percentage of LOI550 and LOI950. The time constrain for the core successions (ca. 1915-2017) was inferred by means of two main elements: correlation with a sediment core extracted about 15 km to the north of our study area and dated using radionuclide dating (210Pb and 137Cs) by (Schuerch et al., 2016) and the presence and depth of shells of Corbícula fluminea (Table 2), invader bivalve first recorded in the RdP estuary by ca. 1970 (Ituarte, 1981). The vertical growth rate of 1.52 cm per year (since year 1960) estimated for that core, that shows a comparable thickness and grain-size trend and represents a similar subaqueous delta subenvironment (Schuerch et al., 2016), was used in the here study sediment cores (Table 3). In a couple of studied cores there is some inconsistency between the two elements, possibly due to a higher rate of sedimentation. Besides, it is important to notice these estimations are relative age that have a degree of uncertainty due to these organisms not necessary may appear in all the sampled sites. The inferred relationships of grain-size subpopulations and sediment transport-deposition, the analysis of the sediment cores (Figs. 6,7) and the evaluation of the geomorphological setting of surficial and core samples, allow proposing a series of lithofacies (Table 2) and facies associations (Table 4). Core location in a time series of aerial photograph and Google Earth® images (Fig. 3) and previous delta models and concepts (mainly those by Wright and Coleman, 1973; Coleman and Wright, 1975; Wright, 1977; Orton and Reading, 1993) were applied in the facies analysis. Principally, the theoretical model of friction-dominated effluents proposed by Wright (1977) can be applied to the PRD, developed in a shallow basin (inner estuary is less than 4 m deep; Urien, 1972; Fig. 2) that promotes turbulent bed friction. The distributary mouth bars are laterally extensive (several km2), with very low slope (Fig. 4a-c) and crossed by shallow tidal channels. Bars are made up of massive or horizontal laminated beds forming heterolithic beds (sandy and muddy silt) and few fine-very fine sand and silty sand (bar crest) (Facies association F1, Table 4; Figs. 6, 7). This is interpreted as quick accumulation of tractive sediments, due to friction at the shallow river mouth, and then reworked by semidiurnal tidal currents and exceptional storm surges and accompanied by settling of fines from suspension. Once these shoals are stabilized by bulrush vegetation the sedimentation is dominated by suspension and particle trapping by vegetation (Fig. 4d), with eventual very low currents. Finally, the bar becomes an island of the lower subaerial delta plain, dominated by accumulation from flooding events. During this final stage clayey silt and silty clay, with the largest values of LOI550 of all core sediments, are deposited by flooding from the distributary channels (Facies association F5). Facies association F2 represents high energy deposition of sand and silty sand, usually with shells, due to exceptional storm surges or fluvial flooding. Deposits of interdistributary bays (Fig. 4e), included in facies association F4, are dominated by horizontal and heterolithic laminated, clayed silt with low LOI550 (Figs. 6,7). Deposits of subaqueous distributary channel (Fig. 4f) are fine-very fine sand and silty sand interlayered with silt and muddy silts with heterolithic laminations (Facies association F3a, Figs. 6,7). In core D11-T2 a succession with interbedded fine-very fine sand and sandy silt-silt with inclined heterolithic stratification (HIS) was identified (Facies association F3b, Fig. 7), and interpreted as subaqueous channel deposits, developed next to distributary bars (Fig. 3e). The textural characterization by means of ME proves to be a convenient technique to interpret mixed sediments like the here studied. Particularly, it can be useful when the sediment sample are acquired with dredges or augers, methods that produce the loss of sedimentary structures but demand less time and logistics than to extract cores. The proposed lithofacies and facies association will allow to systematize the sedimentological studies of the DRP and research of prograding deposits of bayhead deltas fed by big rivers with a sandy silt load.

resumen está disponible en el texto completo

Resumo: Objetivo Esse trabalho tem como objetivo registrar pela primeira vez a presença do berbigão asiático Corbicula fluminea no Rio Poxim-Açu, região nordeste do Brasil. Métodos As amostragens foram realizadas em 20 de outubro de 2016 em cinco pontos ao longo do Rio Poxim-Açu. Em cada ponto foram coletadas cinco amostras com o auxílio de um tudo de PVC (diâmetro de 0,25 m). Todos os indivíduos presentes dentro do tubo foram coletados manualmente. Resultados A espécie esteve presente em todos os pontos amostrais com densidades variando entre 412±169 e 1692±1474 indivíduos/m2. Conclusão Esse registro amplia a distribuição de C. fluminea na região nordeste do Brasil.

Abstract: Aim The objective of this work is to provide a new occurrence record of the Asian clam Corbicula fluminea in the Poxim-Açu River, northeastern Brazil. Methods Samplings were carried out on October 20th of 2016 at five sites along Poxim-Açu River. At each site five samples were taken with a PVC core of 0.25 m of diameter and all individuals found inside core were sorted by hand. Results The species was recorded at all sites with densities ranging from 412±169 to 1692±1474 individuals/m2. Conclusion This record extends the distribution of C. fluminea at northeastern Brazil.

Resumo O mexilhão dourado (Limnoperna fortunei) e Corbicula fluminea são espécies invasoras consideradas bem estabelecidas nos rios do Brasil e da América do Sul. Além dos problemas ambientais resultantes deste processo de invasão, a questão econômica, especialmente nas hidrelétricas, é muito preocupante e mobilizou vários tipos de estudos sobre esses bivalves. A detecção e identificação desses organismos em sua fase adulta nos rios não são um problema, no entanto, a identificação de larvas de bivalves por métodos morfológicos habituais é difícil devido à similaridade extremamente conservada nestes estágios. O uso do PCR-RFLP se mostrou como um método molecular eficiente e ágil que permitiu a detecção de padrões diferentes no gel de agarose para os dois bivalves testados. O padrão do gel mostrou uma banda de 100 pb para L. fortunei que não foi detectado para C. fluminea. Desta forma com o uso de amostras de água é possível detectar os dois moluscos, o que pode ser uma ferramenta poderosa para programas de monitoramento ambiental em espécies aquáticas invasoras.

Abstract The golden mussel (Limnoperna fortunei) and Corbicula fluminea are considered well-established invasive species in the rivers of Brazil and South America. In addition to the environmental problems resulting from this invasion process, the economic issue, especially in hydroelectric dams, is very worrisome and has mobilized several types of studies on these invasive bivalves. The detection and identification of these organisms in their adult phase in the rivers is not a problem; however, the identification of bivalve larvae by usual morphological methods is difficult due to high similarity conserved in these stages. The use of PCR-RFLP has proven to be an efficient and agile molecular method that allowed the detection of different patterns in the agarose gel for the two bivalves tested. The gel pattern showed a 100 bp band for L. fortunei not detected for C. fluminea. Thus, it is possible to detect larvae of these species from water samples, which can be a powerful tool for environmental monitoring programs on aquatic invasive species.

Abstract: First records of the Asian clam Corbicula fluminea (O. F. Müller, 1774) are provided for wetlands in the Papaloapan, Grijalva and Usumacinta basins. A total of 1,668 individuals were colected in 7 localities in Papaloapan, 16 in Grijalva and 24 in Usumacinta basins, sampling was performed from June 2011 to September 2015, in riverine, lacustrine and estuarine wetlands, in a variety of substrates from silt to sand and rocks, and substrates with vegetation. The highest abundances were in lacustrine wetlands and in the Usumacinta watershed. This study contributes with records in 47 localities and also, to the knowledge of exotic species in southern Mexico even when the ecological and economic impacts that this species may cause have not been assessed so far.

Resumen: Se proporcionan nuevos registros de la almeja asiática Corbicula fluminea (O. F Müller, 1774) para los humedales de las cuencas Papaloapan, Grijalva y Usumacinta. Se recolectó un total de 1,668 organismos en 7 localidades de la cuenca Papaloapan, 16 en Grijalva y 24 en Usumacinta, resultado de recolectas desde junio de 2011 hasta septiembre de 2015. Se registra su distribución en humedales ribereños, lacustres y estuarinos, en una diversidad de fondos desde limos hasta arenas, rocas y en sustratos con vegetación. Las mayores abundancias se presentaron para los humedales lacustres y en la cuenca del río Usumacinta. Se contribuye con el registro de 47 localidades en humedales de las cuencas del sureste, incrementando el conocimiento del estado que guardan las especies invasoras en el sureste de México, aun cuando hasta el momento no se han valorado los impactos ecológicos y económicos de las mismas.

Resumo A bacia do rio Guandu é de extrema importância para o estado do Rio de Janeiro, pois abastece grande parte da região metropolitana. Contudo, aspectos malacológicos e ambientais desta bacia são pouco conhecidos. O presente trabalho teve por objetivo realizar um inventário das espécies de moluscos de água doce ocorrentes na região, assim como uma avaliação ambiental através de um Protocolo de Avaliação Rápida, de dez estações de coleta na bacia do rio Guandu em seis municípios (Piraí, Paracambi, Japeri, Seropédica, Queimados e Nova Iguaçu). Foram encontradas 13 espécies, sendo oito nativas (Pomacea maculata, Biomphalaria tenagophila, Gundlachia ticaga, Gundlachia radiata, Omalonyx matheroni, Diplodon ellipticus, Anodontites trapesialis e Eupera bahiensis) e cinco exóticas (Melanoides tuberculata, Ferrissia fragilis, Physa acuta, Corbicula fluminea e Corbicula largillierti). A avaliação ambiental caracterizou a maior parte das estações de coleta como “modificado”. A dispersão das espécies exóticas e os efeitos negativos a elas associados, além da nossa falta de conhecimento sobre as espécies nativas chama a atenção para a necessidade de futuros estudos biológicos e ecológicos das espécies encontradas.

Abstract The Guandu River Basin is extremely important to state of Rio de Janeiro, as a water supplier of several municipalities. However, the malacological knowledge and environmental status is not well known to this basin. The aim of this paper is to present an inventory of freshwater mollusks, as well as an environmental assessment through a Rapid Assessment Protocol, of ten sampling sites at Guandu River basin in six municipalities (Piraí, Paracambi, Japeri, Seropédica, Queimados and Nova Iguaçu). Thirteen species of molusks were found, eight native (Pomacea maculata, Biomphalaria tenagophila, Gundlachia ticaga, Gundlachia radiata, Omalonyx matheroni, Diplodon ellipticus, Anodontites trapesialis and Eupera bahiensis) and five exotics (Melanoides tuberculata, Ferrissia fragilis, Physa acuta, Corbicula fluminea and Corbicula largillierti). The environmental analysis ranked most sites as “modified”. The expansion of exotic species with their associated negative effects, as well the gap in knowledge of native species calls attention to the need of future studies of biology and ecology of the species found.

ABSTRACT In 1981, Corbicula fluminea (Müller, 1774) and C. largillierti (Philippi, 1844) were recorded at the Río de la Plata River. During the 1980’s, C. largillierti was found on a continuous fringe in the shore of that river, while C. fluminea was only found North of Buenos Aires’ harbor. Ten years later, C. fluminea spread to Punta Indio, while C. largillierti remained restricted to tributary streams. The density and size frequency distribution of both species were compared with previous data from samples performed in the same area in 1985-1989. The aim of this research was to determine whether the densities of both species decreased; whether C. fluminea is still more abundant than C. largillierti; and whether the size frequency distributions indicate different population structures from those observed in the end of the 1980’s. Nine localities from the river shore were sampled, and each individual was identified and measured. The size of C. fluminea varied between 2 and 39 mm, showing the highest frequency of individuals between 20 and 25 mm; furthermore the density decreased 90% in 2015/2016. No specimens of C. largillierti were found. In conclusion, the populations of Corbicula inhabiting the Río de la Plata River are retracting.

Resumo O objetivo de deste estudo foi modelar a adequabilidade de habitat do bivalve invasor Corbicula fluminea em uma lagoa costeira na região Neotropical (–30.22, –50.55). A lagoa (19km2, 2,5 m de profundidade máxima) foi amostrada com uma draga Ekman em uma matriz ortogonal compreendendo 84 pontos. Em cada ponto de amostragem foram obtidos descritores ambientais como a profundidade, teor de matéria orgânica (OMC), granulometria média (Avgran), e a percentagem de areia (Pcsand). O poder preditivo dos métodos Modelos Lineares Generalizados (GLM), Modelos Aditivos Generalizados (GAM) e Boosted Regression Trees (BRT) foram comparados. Além disso, a sobreposição de nicho com espécies de moluscos nativos (Castalia martensi, Neocorbicula limosa e Anodontites trapesialis) foi examinada. Um modelo BRT com 1.400 árvores foi selecionado como o melhor modelo, com correlação da validação cruzada de 0,82. As contribuições relativas dos preditores foram Pcsand-42,6%, OMC-35,8%, Avgran-10,9% e profundidade-10,8%. Foi demonstrado que C. fluminea está associada a sedimentos arenosos com pouca matéria orgânica, em áreas rasas próximo às margens. A PCA mostrou uma ampla sobreposição de nicho com as espécies de moluscos nativos C. martensi, N. limosa e A. trapesialis.

Abstract This study aimed to model the habitat suitability for an invasive clam Corbicula fluminea in a coastal shallow lagoon in the southern Neotropical region (–30.22, –50.55). The lagoon (19km2, maximum deep 2.5m) was sampled with an Ekman dredge in an orthogonal matrix comprising 84 points. At each sampling point, were obtained environmental descriptors as depth, organic matter content (OMC), average granulometry (Avgran), and the percentage of sand (Pcsand). Prediction performance of Generalized Linear Models (GLM), Generalized Additive Models (GAM) and Boosted Regression Tree (BRT) were compared. Also, niche overlapping with other native clam species (Castalia martensi, Neocorbicula limosa and Anodontites trapesialis) was examined. A BRT model with 1400 trees was selected as the best model, with cross-validated correlation of 0.82. The relative contributions of predictors were Pcsand-42.6%, OMC-35.8%, Avgran-10.9% and Depth-10.8%. Were identified that C. fluminea occur mainly in sandy sediments with few organic matter, in shallow areas nor by the shore. The PCA showed a wide niche overlap with the native clam species C. martensi, N. limosa and A. trapesialis.

ABSTRACT One of the most important effects derived from the intensive land use is the increase of nutrient concentration in the aquatic systems due to superficial drainage. Besides, the increment of precipitations in South America connected to the global climate change could intensify these anthropic impacts due to the changes in the runoff pattern and a greater discharge of water in the streams and rivers. The pampean streams are singular environments with high natural nutrient concentrations which could be increased even more if the predictions of global climate change for the area are met. In this context, the effect of experimental nutrient addition on macroinvertebrates in a lowland stream is studied. Samplings were carried out from March 2007 to February 2009 in two reaches (fertilized and unfertilized), upstream and downstream from the input of nutrients. The addition of nutrients caused an increase in the phosphorus concentration in the fertilized reach which was not observed for nitrogen concentration. From all macroinvertebrates studied only two taxa had significant differences in their abundance after fertilization: Corbicula fluminea and Ostracoda. Our results reveal that the disturbance caused by the increase of nutrients on the benthic community depends on basal nutrients concentration. The weak response of macroinvertebrates to fertilization in the pampean streams could be due to their tolerance to high concentrations of nutrients in relation to their evolutionary history in streams naturally enriched with nutrients. Further research concerning the thresholds of nutrients affecting macroinvertebrates and about the adaptive advantages of taxa in naturally eutrophic environments is still needed. This information will allow for a better understanding of the processes of nutrient cycling and for the construction of restoration measures in natural eutrophic ecosystems.

RESUMEN Uno de los efectos más importantes derivados del uso intensivo de la tierra es el aumento de la concentración de nutrientes en los sistemas acuáticos debido al escurrimiento superficial. Además, el incremento de las precipitaciones en América del Sur vinculado al cambio climático global podría intensificar estos impactos antrópicos debido a los cambios en los patrones de escurrimiento y una mayor descarga de agua en los arroyos y ríos. Los arroyos pampeanos son ambientes particulares, con altas concentraciones basales de nutrientes, que podrían incrementarse aún más si las predicciones del cambio climático global se cumplen. En este contexto, se estudió el efecto de la adición experimental de nutrientes en un arroyo pampeano sobre los macroinvertebrados. Los muestreos se llevaron a cabo entre marzo de 2007 y febrero de 2009 en dos tramos seleccionados, aguas arriba y aguas abajo de la entrada de nutrientes. La adición de nutrientes causó un aumento en la concentración de fósforo en el tramo fertilizado, lo que no se observó para la concentración de nitrógeno. De todos los macroinvertebrados estudiados sólo dos taxa tuvieron diferencias significativas en su abundancia después de la fertilización: Corbicula fluminea y ostrácodos. Nuestros resultados revelaron que la perturbación causada por el aumento de nutrientes en una comunidad bentónica depende de la concentración basal de nutrientes. La respuesta débil de macroinvertebrados a la fertilización en las corrientes pampeanas podría ser debido a su tolerancia a altas concentraciones de nutrientes de acuerdo a su historia evolutiva en arroyos enriquecidos naturalmente con nutrientes. Se necesitan nuevas investigaciones sobre los umbrales a partir de los cuales los macroinvertebrados podrían verse afectados y sobre las ventajas adaptativas de los taxones en ambientes eutróficos naturales. Esta información nos permitirá comprender mejor los procesos de reciclaje de nutrientes y así poder pensar medidas de restauración de ecosistemas eutróficos naturales.

Corbicula fluminea é um bivalve invasor, responsável por inúmeros problemas ambientais e econômicos ao redor do mundo. Apesar de sua capacidade de invasão, a espécie sofre certas restrições devido a fenômenos naturais em ambientes lênticos, afetando significativamente sua estrutura populacional (e.g. flutuação do nível da água e a exposição à luz solar). O presente trabalho avaliou como o decréscimo temporal do nível da água de um reservatório neotropical e a exposição solar, afeta a estrutura populacional de C. fluminea. Duas amostragens foram realizadas no reservatório da Usina Hidrelétrica (UHE) de Furnas (Minas Gerais, Brasil), em 2011 e 2012. A densidade populacional, o comprimento médio e a distribuição espacial da espécie para cada ano foram estimados após amostragem em 51 quadrats (0,0625m2) dispostos em três transectos em diferentes distâncias das margens do reservatório (0, 10 e 20 m em relação a um ponto fixo). Observou-se o predomínio de C. fluminea em ambos os anos, coincidindo com o decréscimo da densidade e riqueza de espécies nativas nas áreas de amostragem. Foram registradas diferenças significativas na densidade de C. fluminea entre as distâncias da margem, sendo atribuídas principalmente à variabilidade temporal do substrato e da água desses ambientes. Registrou-se também uma tendência em aumento da densidade e agregação com o aumento da distância da margem, devido à maior estabilidade dessas áreas (>10 m). Houveram diferenças significativas no tamanho médio das conchas de C. fluminea entre às distâncias da margem e durante os anos, assim como na interação desses fatores (Distâncias vs. Anos). Tais resultados foram associados à capacidade reprodutiva e invasiva da espécie. Esse estudo revelou que eventos temporais (principalmente, a flutuação do nível da água) em ambientes lênticos neotropicais provocam alterações na densidade, tamanho médio e distribuição de C. fluminea e na composição da malacofauna nativa.

Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.

Corbicula fluminea é um bivalve exótico natural da Ásia que espalhou-se rapidamente pelo mundo tornando-se uma espécie invasora altamente agressiva em muitos países. A espécie tem o potencial de provocar uma série de impactos ecológicos, econômicos e sociais como a extinção de espécies nativas, alterações em ecossistemas e danos em tubulações e turbinas de hidrelétricas. Como exemplo dos danos que a espécie pode gerar, basta mencionar que o governo dos Estados Unidos gasta anualmente mais de 1 bilhão de dólares com a espécie. Os objetivos deste trabalho foram registrar a primeira ocorrência do bivalve invasor C. fluminea na bacia do rio Jundiaí-Mirim, SP, Brasil bem como contribuir com alguns dados ecológicos básicos como densidade, distribuição de frequências de tamanho bem como a distribuição da espécie ao longo da bacia hidrográfica. Um total de 78 indivíduos foi coletado com draga van Veen. Os organismos foram identificados e medidos. O molusco foi registrado em apenas duas das quatro estações amostrais e sua distribuição provavelmente relaciona-se com a composição do sedimento e fluxo da água. Valores intermediários de densidade foram registrados variando de 12 a 235 ind.m-2. Os dados sugerem populações jovens que estão em crescimento na bacia. A presença de C. fluminea é uma questão preocupante no que concerne a manutenção do ecossistema e da água para diferentes usos na região de Jundiaí, SP.

Corbicula fluminea is a naturally occurring Asian bivalve that was spread around the world, and which has become a highly aggressive invasive species in many countries. C. fluminea has many ecological, economic and social impacts, such as the extinction of native species, ecosystems alterations, and damage to pipes and hydropower turbines. As an illustration of the potential damage that proliferation of C. fluminea can cause, it is noted that the United States government spends more than 1 billion dollars per year to control this species. This work recorded the first occurrence of the Asian clam C. fluminea in the Jundiaí-Mirim Basin, SP, Brazil, and included basic ecological information such as density, frequency distribution of size and species distribution along the basin. Seventy-eight individuals were sampled with a van Veen grab along the basin. The specimens were identified and measured. The exotic species was found only in two of four sampling points and its distribution was possibly influenced by sediment composition and water flow. Moderate densities were calculated, ranging from 12 to 235 ind.m-2. Our data suggest that young populations are growing in the basin. The presence of C. fluminea is a concern for the maintenance of the ecosystem and for different water uses in the Jundiai region.

A composição da dieta de 66 espécies de peixes foi investigada de setembro de 2009 a junho de 2010, em três subsistemas da planície de inundação do alto rio Paraná (Brasil), após a invasão das espécies de molusco Limnoperna fortunei (Dunker, 1857) e Corbicula fluminea (Müller, 1774), e da macrófita Hydrilla verticillata (L.f.) Royle. Limnoperna fortunei foi consumida em todos os subsistemas amostrados e ocorreu na dieta de 15 espécies de peixes, com grande participação na dieta de Leporinus obtusidens. Corbicula fluminea esteve presente na dieta de Pterodoras granulosus coletados nos subsistemas Paraná e Ivinheima. Hydrilla verticillata ocorreu na dieta de Schizodon nasutus, capturados nos subsistemas Ivinheima e Paraná. Até o momento não é possível avaliar o potencial destas espécies para controlar moluscos invasores na área de estudo ou o impacto destas espécies sobre a estrutura das cadeias alimentares. Peixes omnívoros e herbívoros da área de estudo podem ter pouco impacto sobre a população de H. verticillata.

The composition of the diets of 66 species of fishes was investigated from September 2009 to June 2010 in three subsystems of the Upper Paraná River floodplain (Brazil), following invasion by the two mollusk species Limnoperna fortunei (Dunker, 1857) and Corbicula fluminea (Müller, 1774), and the macrophyte Hydrilla verticillata (L.f.) Royle. Limnoperna fortunei was consumed in all three subsystems and occurred in the diet of 15 fish species, with a high proportion in the diet of Leporinus obtusidens. Corbicula flumineawas present in the diet of Pterodoras granulosus caught in the Paraná and Ivinheima subsystems. Hydrilla verticillataoccurred in the diet of Schizodon nasutus caught in the Ivinheima and Paraná subsystems. It is not yet possible to evaluate the potential of these species to control invasive mollusks in the study area or the impact of these species on the structure of the food chain. Omnivorous and herbivorous fishes in the study area may have little impact on the population of H. verticillata.

Introduction Schistosomiasis is a parasitic disease of public health concern in Brazil, and the construction of hydroelectric dams, in addition to increasing permanent human settlement and tourism, has created conditions suitable for the establishment of mollusks that can transmit schistosomiasis. Such areas require a number of actions to prevent the establishment of schistosomiasis. This paper reports on a freshwater malacological survey carried out in the geographical area of the Manso Power Plant. Methods Mollusks were collected in 18 municipalities in the State of Mato Grosso between February 2002 and February 2004 (qualitative study) and from April 2009 to February 2011 (quantitative study). Results Thirty-one species of mollusks were collected, including newly recorded species (Antillorbis nordestensis and Burnupia ingae). In addition, the geographic distributions of known species, including Biomphalaria straminea, a snail vector of Schistosoma mansoni, were expanded. A total of 4,507 specimens were collected in the APM Manso reservoir (Usina Hidrelétrica de Aproveitamento Múltiplo de Manso) during the quantitative study, and Biomphalaria amazonica was found in six of the 10 localities analyzed. The Afroasiatic species Melanoides tuberculata, introduced after February 2009, was the dominant species (relative abundance 94.96%). Conclusions The study area is epidemiologically important due to the occurrence of B. straminea and B. amazonica, which are vectors of schistosomiasis, and M. tuberculata, a snail host of Centrocestus formosanus, which is responsible for centrocestiasis transmission. Observations of M. tuberculata and the exotic freshwater clams Corbicula fluminea and Corbicula largillierti raise concerns about biodiversity.

A disponibilização de sedimentos nos cursos d'água, em função dos processos erosivos que ocorrem no entorno, constitui-se e uma das principais fontes de poluição e alteração das condições físico-químicas dos recursos hídricos. Além disso, o aumento da turbidez da água pode causar assoreamento, impactando drasticamente as comunidades aquáticas. Especificamente para o bivalve Corbicula fluminea (MÜLLER, 1774), este estudo teve por objetivo analisar o efeito da exposição a diferentes condições de turbidez, como fator de risco para os animals. Para esta finalidade, um dispositivo de acoplamento foi concebido para assegurar a circulação da água, em um sistema fechado mantendo os níveis desejados de turbidez. Embora C. fluminea possa tolerar mudanças ambientais em sistemas aquáticos, foi observadao experimentalmente, uma intolerância a turbidez acima de 150 unidades nefelométricas de turbidez (NTU), um valor próximo ao registrado em pontos de estudo nos rios Pardo (Serrana-SP-Brasil) e Mogi Guaçu (Porto Ferreira-SP-Brasil) durante a estação chuvosa. Por intermédio da utilização de um modelo de regressão logística, os resultados experimentais foram analisados. As taxas de mortalidade observadas indicam ser a exposição dos animais a níveis de turbidez acima desse limite e por períodos mais longos do que 120 horas uma provável causa de mortalidade desta espécie.

The provision of sediment in rivers, due to erosion processes that occur in the environment, consists of a major source of pollution and alteration of the physicochemical conditions of water resources. In addition, the increase in water turbidity may cause siltation, dramatically impacting aquatic communities. Specifically considering the bivalve Corbicula fluminea (Müller, 1774), the aim of this study was to analyse the effect of exposure to different turbidity conditions of sediments, as a risk factor for the animals. For this purpose, a docking device was designed to ensure water circulation in a closed system and to maintain the desired levels of turbidity. Although C. fluminea can generally tolerate environmental changes in aquatic systems, an intolerance to high turbidity levels was experimentally observed, expressed by the mortality rate of the animals when exposed to conditions above 150 nephelometric turbidity units (NTU). This value was similar to the one recorded at study sites in the rivers Pardo (Serrana-SP-Brazil) and Mogi Guaçu (Porto Ferreira-SP-Brazil) during the rainy season. Using a logistic regression model, the experimental results were analysed and the observed mortality rates indicate that the exposure of the animals to turbidity levels above 150 nephelometric turbidity units (NTU), for periods longer than 120 hours, may be considered a probable cause of mortality for the species.