Abstract Benthic macroinvertebrates are organisms that are recognized as water quality bio-indicators. A wide variety of indices and metrics have been shown to respond to a variety of anthropogenic impacts, usually under a general condition of environmental impairment. The absence of a clear distinction in the relations between specific pollutants and biotic variables is very common and can lead to biased interpretation of biomonitoring. The aims of this research were to test taxonomic and non-taxonomic responses to specific environmental conditions instead to general conditions. For this purpose, we estimated the theoretical toxicity by comparing toxicity values published by EPA with metal concentrations in water and sediments. Then we tested the responses of biological variables to toxicity and other environmental conditions using the linear mixed effects models approach. We generated 32 models considering 24 different biological metrics and indices that were grouped in five levels. Taxonomic and abundance metrics were best predictor than functional or tolerance-based indexes. The strongest model was that which considered subfamily taxonomic resolution responding to Al_w and Cr_s.

Resumo: O objetivo deste trabalho foi analisar a distribuição da comunidade de oligoquetos em relação às variáveis físico-químicas da coluna da água, variação estrutural do ambiente, e substratos predominantes em riachos amazônicos conservados na FLONA Saracá-Taquera, noroeste do Pará, Brasil. Oligochaetes são amplamente utilizados como bioindicadores para monitoramento de ambientes aquáticos, pois são muito sensíveis à poluição e às mudanças ambientais. Variáveis físico-químicas e estruturais de 100 trechos de riachos foram mensuradas para entender a distribuição de oligoquetos em riachos amazônicos. Amostras bióticas foram coletadas com amostrador Surber em três dos tipos de substratos mais predominantes em cada trecho. A PERMANOVA mostrou que há uma diferença significativa da comunidade de oligoquetos entre alguns substratos, possivelmente baseada nas diferenças no número do táxon mais comum. A Análise de Correspondência Canônica mostrou que as variáveis físicas controlam a distribuição da comunidade de oligoquetos em riachos amazônicos preservados, porque estas variáveis determinam a formação dos diferentes substratos ao longo do riacho, desde a nascente até a foz, favorecendo a presença de oligoquetos com necessidades ecológicas mais específicas em riachos de baixa ordem, e oligoquetos capazes de colonizar diferentes tipos de substrato e zonas mais profundas em riachos de ordem maior. Os resultados deste trabalho sugerem que a profundidade da água e a largura do canal são as variáveis que controlam a distribuição da comunidade de oligoquetos em riachos amazônicos, determinando a formação de substratos instáveis e de baixa qualidade, e consequentemente baixa colonização de oligoquetos, em riachos de ordem maior; e formação de substratos mais diversificados, mais estáveis e de qualidade em riachos de baixa ordem, favorecendo a colonização de diversos taxa de oligoquetos aquáticos em riachos amazônicos de baixa ordem.

Abstract: The aim of this study was to analyze aquatic oligochaete distribution in relation to water column physicochemical variables, structural environmental variation, and predominant substrates in the preserved Amazonian streams of the Saracá-Taquera National Forest (FLONA Saracá-Taquera), northwest Pará, Brazil. Oligochaetes are widely used as bioindicators for monitoring aquatic environments as they are very sensitive to pollution and environmental changes. Physicochemical and structural variables were measured from 100 stream segments in order to understand the distribution of oligochaetes in Amazonian streams. Biotic samples were collected using Surber samplers in three of the most predominant substrate types in each segment. PERMANOVA testing showed that there was a significant difference in the oligochaete community among some substrates, potentially caused by a difference in the abundance of the most common taxa. Canonical Correspondence Analysis showed that physical variables drive the distribution of oligochaetes in preserved Amazonian streams, as they determine the formation of different substrates along the stream, from the source to the mouth; favoring the presence of oligochaetes with more specific ecological needs in low-order streams, and the presence of oligochaetes capable of colonizing various types of substrates and deeper zones in high-order streams. These results suggest that water depth and channel width are the main drivers of aquatic oligochaete distribution along Amazonian streams, determining the formation of unstable and low-quality substrates and, consequently, the low colonization by oligochaetes in high-order streams; and more diverse and stable substrate formation in low-order streams, favoring the colonization by diverse taxa of aquatic oligochaetes in low-order Amazonian streams.

Resumo Objetivo: Nosso objetivo neste estudo foi avaliar os efeitos da regulação do fluxo de um rio semi-árido utilizado para irrigação sobre as assembleias de macroinvertebrados. Métodos Nós amostramos duas seções no rio Dulce River, um trecho localizado a montante da barragem de desvio em Los Quiroga e outro a justante, para avaliação da descontinuidade fluvial. Nós avaliamos as diferenças entre os trechos e sítios de amostragem com relação às variáveis ambientais, a densidade de invertebrados, a riqueza e o índice de Shannon aplicando análise de variância não-paramétrica de Kruskal-Wallis. A Análise de Porcentagem de Similaridade (SIMPER) foi usada para identificar quais espécies contribuiram para as dissimilaridades da estrutura das assembleias de macroinvertebrados. A Análise de Correspondência Canônica (CCA) foi executada com o conjunto total de amostras para explorar a distribuição dos macroinvertebrados nos trechos e as associações das assembleias com as variáveis do habitat. Resultados Os valores da densidade, da riqueza e do índice de Shannon não mostraram diferenças entre os trechos a montante e a jusante da barragem de desvio. A diversidade beta (Whittaker) foi de 0,72 entre os locais à montante, 0,56 entre os locais a justante e a maior taxa de reposição de espécies (0,73) foi obtida ente ambos os trechos. A Análise de Correspondência Canônica explicou 46,71% da variância diferindo os locais a montante explicados pelos altos valores de matéria orgânica do sedimento e descarga, altas densidades de Nais communis, Bothrioneurum americanum, Pelomus, Stephensoniana trivandrana, Pristina menoni, P. jenkinae, P.longidentata, P. americana, Dero obtusa, Endotribelos, Heleobia e Turbellaria. Os sítios de amostragem a jusante estiveram associadas a substrato mais grosseiro e densidade maior de Lopescladius, Polypedilum, Cricotopus, Thienamaniella, Cryptochironomus, Baetidae, Nematoda e Corbicula fluminea. Conclusão O distúrbio de baixo fluxo teve efeitos sobre a composição das assembleias de invertebrados bentônicos, mas também atributos (tais como densidade e riqueza) apresentaram menor variabilidade provavelmente devido à reposição de táxons.

Abstract Aim: Our aim in this study was evaluate the effects of flow regulation for irrigation on the macroinvertebrate assemblages in a semiarid river. Methods We sampled two reaches in Dulce River; one placed upstream a weir that diverts flow into a network of irrigation channels and the other downstream that weir, in the assessment of the fluvial discontinuity. We assess the differences among reaches and sites, environmental variables, invertebrate density, richness and Shannon-Wiener index applying non-parametric analyses of variance Kruskal Wallis. The similarity percentage analysis (SIMPER) was used to identify which species contributed to the dissimilarities on macroinvertebrate assemblage structure. Canonical Correspondence Analysis (CCA) was performed with the total set of samples to explore macroinvertebrate distribution in reaches and associations of the assemblages with habitat variables. Results The density, richness and Shannon index values did not show differences between the reaches located upstream and downstream. Beta diversity (Whittaker) was 0.72 among upstream sites, 0.56 among downstream sites and higher species turnover (0.73) was obtained between both reaches. The Canonical Correspondence Analysis explained 46.71% of the variance differentiating upstream sites explained by higher values of organic matter of bottom sediments and discharge, high density of Nais communis, Bothrioneurum americanum, Pelomus, Stephensoniana trivandrana, Pristina menoni, P. jenkinae, P.longidentata, P. americana, Dero obtusa, Endotribelos, Heleobia and Turbellaria. The downstream sites were associated to coarser substratum and higher density of Lopescladius, Polypedilum, Cricotopus, Thienamaniella, Cryptochironomus, Baetidae, Nematoda and Corbicula fluminea. Conclusions The low-flow disturbance had effects on the composition of the benthic invertebrate assemblages, but attributes (such as density and richness) showed a lower variability probably because of taxa replacement.

ABSTRACT Functional classification of animals is necessary to enhance the predictive power of food web models. However, while there is a large database for functional classification of benthic invertebrates (Functional Feeding Groups, FFG) in the temperate zone, the attribution of individual species of riverine invertebrates is still in its infancies in the Neotropical Region. Different authors hypothesized that diet breadth was larger in the Tropics, however detailed analysis are scarce. In the present study we aimed at classifying dominant benthic taxa of the Middle Paraná River floodplain (Argentina) into trophic guilds by diet and niche overlap analyses. We sampled twelve taxa of benthic invertebrates from a floodplain lake during low water season and performed a gut content analysis as a baseline for FFG classification. We also used available diet information of other common taxa for statistical analysis. Then, we compared the variance of niche overlap, using Pianka's index, with that of simulated null model. After that we grouped taxa using Morisita similarity index with a threshold of 0.6 and compared niche overlap with null models within and between FFGs. Observed variance of niche overlap was greater than expected by chance, confirming the presence of FFGs among analyzed taxa. Considering trophic similarity of species, we identified four FFGs: collectors, omnivores, herbivores and predators. Niche overlap was greater than expected by stochastic null models within FFGs, and smaller between FFGs. Nearly one third of analyzed taxa were classified in a different FFG than their congeners of the Holarctic region. This result indicates that classifications performed in the Holarctic region should be used with care in the Neotropical region, even in subtropical systems

Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River. The Orthoptera assemblage composition varies considerably, depending on habitat type. This study examines the spatiotemporal relationship between plant diversity, hydrometric level, environmental variables and the Orthoptera richness and abundance in floodplain lakes connected permanently or temporarily with the main channel of the Paraná River. The grasshoppers were collected fortnightly (April 2006May 2007). A total of 17 species were recorded and classified according to their frequency of occurrence in constant (7), accessory (4), or accidental (6) species. In the two lakes, the greater species richness and abundance was recorded in summer, thereby coinciding with the highest water level of the Paraná River. The most significant correlation between the orthopteran richness and abundance was with the water level. The aquatic plant richness was significantly different between the lakes, but the vegetation was dominated by Eichhornia crassipes (Mart.) Solms. (Liliales, Pontederiaceae). The lake, which was connected permanently, presented the highest values of diversity and abundance, proving to be a more diverse assemblage. The beta diversity was higher in the temporary connected lake than in the permanently connected one. The orthopterans assemblages were different between the lakes, Cornops aquaticum and Tucayaca gracilis were the species that contributed more to the level of dissimilarity. C. aquaticum was more representative in the lake temporarily connected, while T. gracilis in the permanent connected one. The water level of the Paraná River and the connectivity of the floodplain lakes play an important role to explain the abundance and richness of their orthopteran assemblages.

The gut contents of nine genera of benthic Chironominae and Tanypodinae from the Middle Paraná River floodplain habitats (a lake and a secondary channel) were analyzed to determine their feeding patterns and functional feeding groups. Amorphous detritus, animal and vegetal tissues, and mineral materials (predominantly sand) were observed in the larval guts. Amorphous detritus were the main food item found for Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp., and Pelomus sp. (Chironominae), while animal tissues (mainly oligochaetes) were the most important food item found for Ablabesmyia (Karelia) sp., Coelotanypus sp., and Procladius sp. (Tanypodinae). Dietary overlap was calculated for all pairs of genera. Within predators, the highest overlap was obtained between Coelotanypus sp. and Ablabesmyia (Karelia) sp., while within detritivores the highest niche overlap was obtained between Endotribelos sp. and Phaenopsectra sp.

Se analizó el contenido intestinal de nueve géneros de Chironominae y Tanypodinae bentónicos en ambientes de la llanura aluvial del río Paraná Medio (laguna y cauce secundario) para determinar su patrón alimentario y los grupos funcionales tróficos. En los contenidos intestinales se observaron detrito amorfo, material mineral (principalmente arena), tejidos vegetal y animal. El principal ítem alimentario encontrado en Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp. y Pelomus sp. (Chironominae) fue detrito amorfo, mientras que en Ablabesmyia (Karelia) sp., Coelotanypus sp. y Procladius sp. (Tanypodinae) el ítem más importante fue tejido animal (principalmente restos de oligoquetos). Se calculó el solapamiento trófico entre todos los pares de géneros, obteniéndose el mayor solapamiento dentro de los depredadores entre Coelotanypus sp. y Ablabesmyia (Karelia) sp. y dentro de los detritívoros entre Endotribelos sp. y Phaenopsectra sp.

The larvae of Chironomidae are very important due to their density and role in aquatic food webs. Goeldichironomus holoprasinus Goeldi is one of the most abundant species of Chironomidae in man-made and natural systems, being widely used in water quality assessments. Because of its tolerance to stressing environmental factors, many studies have investigated the effects of stressors on G. holoprasinus anatomy and bionomic attributes. The main aim of this work was to describe G. holoprasinus life cycle attributes in laboratory conditions. The cephalic capsule growth among instars was 1.64 in average (Dyar proportion), whereas the total size growth was continuous. The average room temperature registered was 26ºC (18-33ºC). In this conditions the D value (time from oviposition to first imago emergence) was 13 days, whereas the minimum G value (interval from the oviposition to the first progeny of the next generation) was 16 days. The emergence lasted four days, which determined that average G of 18 days. Thus, at registered temperatures G. holoprasinus has a short life cycle.

Las larvas de Chironomidae son muy importantes en los ambientes acuáticos continentales por su abundancia y por su rol en las tramas tróficas. Goeldichironomus holoprasinus Goeldi es una de las especies más abundantes de Chironomidae en ambientes urbanos y naturales, siendo indicadora de calidad de ambientes. Por su tolerancia a factores ambientales estresantes muchos estudios se han realizado en relación con los efectos en su anatomía y atributos bionómicos. El objetivo principal de este estudio fue establecer las características del ciclo de vida de G. holoprasinus en condiciones de laboratorio. El crecimiento de las dimensiones cefálicas entre estadios tuvo una razón de 1,64 en promedio (proporción de Dyar), mientras que el crecimiento en longitud fue continuo. La temperatura promedio medida en el laboratorio de cría fue de 26ºC (18-33ºC). En estas condiciones el valor de D (tiempo de desarrollo desde la oviposición a la emergencia del primer imago) fue de 13 días y el valor de G mínimo (intervalo desde la oviposición a la primer progenie de la siguiente generación) fue de 16 días.

Eucalyptus camaldulensis leaves collected at abscission and 6 g dry weight were placed innylon bags of 5 mm mesh net in a secondary channel of Middlle Parana River (31° 40'S y 60° 33' W). Three replicates were collected after 7, 14, 28, 56 and 112 days during low water level (may-september 2002). The decay coefficient (k) calculated over 112 days was 0.0131 d-1. The time estimated for 95% of leaves decomposition was 36 days according to the k obtained. The highest invertebrate density (600 ind.g-1 of leaves dry weight) and taxonomic richness (39 taxa) were obtained at 112 days and 14 days of leaf decomposition, respectively. The colonization on decomposing leaves was dominated by chironomids and mussels. Gatherers-collectors (Naididae and Chironominae) were dominant during the first time and filterers-collector (Limnoperna fortunei) increasing at the end of colonization experiment. The shredders (Polypedilum spp.) were more abundant in the first and media colonization phases.

Hojas de Eucalyptus camaldulensis, fueron recolectadas después de la abscisión y se colocaron 6 g de hojas secas en bolsas de nylon de 5 mm de abertura de malla en un cauce secundario del río Paraná medio (31° 40'S y 60° 33' O). Se extrajeron 3 réplicas a los 7, 14, 28, 56 y 112 días durante un período de estiaje del agua (mayo-septiembre, 2002). El coeficiente de descomposición (k) fue de 0.0131 d-1 a los 112 días. El tiempo necesario estimado para que se descomponga el 95% del material vegetal fue de 36 días, teniendo en cuenta el coeficiente k obtenido. La mayor densidad de invertebrados (600 ind.g-1 de peso seco de hojas) y riqueza taxonómica (39 taxa) fueron obtenidas a los 112 y 14 días de exposición, respectivamente. Los quironómidos y bivalvos fueron los taxa dominantes en la colonización de hojas en descomposición. Los colectores - recolectores (principalmente Naididae y Chironominae) dominaron las primeras etapas de la sucesión y los colectores - filtradores (Limnoperna fortunei) aumentaron notablemente en las etapas finales. Mientras que los trituradores (Polypedilum spp.) fueron más abundantes durante las primeras fases de la colonización.

Las larvas de quironómidos son componentes importantes de la biota acuática por su participación en las tramas tróficas y por ser bioindicadores de condiciones ambientales. Muchos estudios de laboratorio han analizado los efectos de diferentes contaminantes sobre quironómidos, especialmente sobre Chironomus calligraphus Goeldi, 1905. Sin embargo, poco se conoce sobre los atributos de su ciclo de vida. El objetivo de este estudio fue analizar el ciclo de vida de C. calligraphus en condiciones de laboratorio. La razón de crecimiento entre estadios larvales fue aproximadamente constante (r= 1,60 ±0,02), el tiempo de desarrollo (D) fue 15 días y el tiempo mínimo de generación (G) fue 18 días. De acuerdo a estos resultados y a observaciones realizadas en campo, C. calligraphus es una especie con ciclo de vida temperatura-dependiente con generaciones superpuestas de corta duración en primavera-verano y con una o dos generaciones de mayor duración en invierno.

Chironomid larvae are important components of aquatic biota, due to their abundance and participation in food webs, and because they are considered environmental bioindicators. Many laboratory studies have analyzed the effects of pollutants on chironomids, especially on Chironomus calligraphus Goeldi, 1905. However, little is known about the life cycle attributes of Chironomidae (Diptera). The main pourpose of this study was to analyze C. calligraphus life cycle under laboratory conditions. The growth rate was almost constant between larval instars (r= 1.60 ±0.02), the immature development time (D) was 15 days and the minimum generation time (G) was 18 days. According to these results and field observations C. calligraphus has a temperature-dependent life cycle, with several overlapped short duration cohorts in spring-summer followed by one or two generations of longer duration in winter.

As larvas de quironomídeos são componentes importantes da biota aquática por sua participação nas tramas tróficas e por serem bioindicadores de condições ambientais. Muitos estudos de laboratório têm analisado os efeitos de diferentes contaminantes sobre quironomídeos, especialmente sobre Chironomus calligraphus Goeldi, 1905. No entanto, pouco se conhece sobre os atributos de seu ciclo de vida. O objetivo deste estudo foi analisar o ciclo de vida de C. calligraphus em condições de laboratório. A razão de crescimento entre estágios larvais foi aproximadamente constante (r= 1,60 ±0,02), o tempo de desenvolvimento (D) foi de 15 dias e o tempo mínimo de geração (G) foi de 18 dias. De acordo a estes resultados e a observações realizadas em campo, C. calligraphus é uma espécie com ciclo de vida temperatura-dependente com gerações superpostas de curta duração em primavera-verão e com uma ou duas gerações de maior duração no inverno.

Estudos sobre macroinvertebrados bentônicos de ambientes lóticos geralmente focam na ocorrência, distribuição e riqueza de insetos aquáticos e de crustáceos decápodos. Tais estudos apenas raramente incluem Oligochaeta. O objetivo do presente estudo foi examinar a ocorrência e riqueza de espécies de Oligochaeta de diferentes substratos em ambientes lóticos. O estudo incluiu sete riachos do Parque Estadual Intervales (São Paulo, Brasil). Os riachos estudados variaram em tamanho desde primeira até quarta ordem. Em cada ambiente, foram realizadas coletas qualitativas utilizando amostrador do tipo rede em D com malha 0,21 mm. Simultaneamente às coletas de Oligochaeta foram tomadas medidas do pH, condutividade elétrica, oxigênio dissolvido, temperatura e turbidez da água dos ambientes. Foram coletados exemplares das famílias Tubificidae (incluindo Naidinae) e Enchytraeidae. Os Tubificidae Aulodrilus limnobius, Limnodrilus neotropicus e Limnodrilus hoffmeisteri estiveram associados à habitats com pouca correnteza e substrato contendo material orgânico fino. Nais communis espécie mais representativa entre os Naidinae, esteve predominantemente associada a substratos rochosos presentes em locais de correntes rápidas. As duas outras espécies de Naidinae, Pristina osborni e Amphichaeta leydigi apresentaram baixa freqüência nos córregos analisados. A família Enchytraeidae esteve presente somente em um dos ambientes amostrados.

Studies on benthic macroinvertebrates of lotic environments usually focus on the occurrence, distribution, and richness of aquatic insects and decapod crustaceans. Only rarely these studies include the Oligochaeta. The aim of the present study was to examine the occurrence and species richness of Oligochaeta in different substrata patches of lotic environments. The studied included seven stream sites at Parque Estadual Intervales (São Paulo, Brazil). Stream sites differed in size and ranged from first to fourth order. In each stream, qualitative collections were made using a D-type net sampler with 0.21 mm mesh. Measures of pH, electrical conductivity, dissolved oxygen, temperature and water turbidity were taken in the studied sites during collections of Oligochaeta. Specimens of the Tubificidae (including Naidinae) and Enchytraeidae families were collected. The Tubificidae Aulodrilus limnobius, Limnodrilus neotropicus and Limnodrilus hoffmeisteri were associated with low-flow habitats containing fine organic material. The most representative species among the Naidinae, Nais communis, was predominantly associated with rocky substrates present in fast current locations. The two other Naidinae species, Pristina osborni and Amphichaeta leydigi, presented low frequency in the studied streams. The Enchytraeidae family was present in only one of the sampled habitats.

Se analizó la descomposición de hojas de Tessaria integrifolia y su colonización por invertebrados en el río Tiradero Viejo, cauce secundario del río Paraná, Argentina. Las hojas de T. integrifolia fueron recolectadas después de la abscisión; se colocaron 6g de hojas secadas al aire en bolsas de nylon de 5mm de abertura de malla y fueron expuestas al proceso de descomposición en la ribera del río. Se extrajeron 3 réplicas a los 7, 14, 28, 56 y 112 días. El coeficiente de descomposición (k) obtenido fue de 0,0143 a los 112 días. La densidad máxima de invertebrados fue de 395 individuos/g de peso seco de hojas a los 56 días de exposición. La mayor riqueza de especies y diversidad fueron obtenidas a los 28 días, siendo los oligoquetos (Pristina leidyi, P. aequiseta, Dero multibranchiata), quironómidos (Polypedilum spp., Phaenopsectra sp.) y bivalvos (Limnoperna fortunei) los taxa dominantes. Los colectores-recolectores fueron dominantes durante las primeras etapas de la sucesión y los colectores-filtradores aumentaron en las etapas finales, mientras que los trituradores fueron escasos pero más constantes a lo largo de la experiencia.

The decomposition of leaf litter of Tessaria integrifolia and its colonization by invertebrates were studied in the Tiradero Viejo River. Leaves were collected at abscission and 6g dry weight and were placed in nylon bags with 5 mm mesh net. Samplings were carried out between May and September 2002 and three replicates were collected after 7, 14, 28, 56 and 112 days. The decay coefficient calculated over 112 days of decomposition was 0.0143d-1. Invertebrate densities increased with the progressive decomposition of the leaves, reaching the maximum at 56 days (395 individuals/g of leaves dry weight). The highest species richness (43) and Shannon’s index (4.24) were obtained at 28 days of leaf decomposition. Colonization of decomposing leaves was dominated by oligochaetes (Pristina leidyi, P. aequiseta, Dero multibranchiata), chironomids (Polypedilum spp., Phanopsectra sp.) and mussels (Limnoperna fortunei). Gatherers-collector were dominant during the first time, the filterers increasing at the end of the colonization experiment and the shredders were more constant over time but scarce.

Analisou-se a decomposição de folhas de "Tessaria integrifólia" e sua colonização por invertebrados no rio "Tiradero Viejo", canal secundário do rio Paraná, Argentina. As folhas de T. integrifolia foram recolhidas depois da abscisão; se colocaram 6g de folhas secas ao ar em bolsas de nylon furadinho com aberturas de 5mm e foram expostas ao processo de decomposição na ribeira do rio. Extraíram-se 3 réplicas aos 7, 14, 28, 56 e 112 dias. O coeficiente de decomposição (k) obtido foi de 0,0143 aos 112 dias. A densidade máxima de invertebrados foi de 395 indivíduos/g de peso seco folha aos 56 dias de exposição. A maior riqueza de espécies e diversidade for obtida aos 28 dias, sendo os oligoquetos (Pristina leidyi, P. aequiseta, Dero multibranchiata), quironomídeos (Polypedilum spp., Phaenopsectra sp.) e bivalves (Limnoperna fortunei) os taxa dominantes. Os coletores-recoletores foram dominantes durante as primeiras etapas da sucessão e os coletores-filtradores aumentaram nas etapas finais, enquanto que os trituradores foram escassos, embora mais constantes ao longo da experiência.

Apesar da importância dos Oligochaeta para a dinâmica dos ecossistemas aquáticos e para os estudos sobre a biologia da poluição, existe atualmente, no Brasil, uma carência de informação sobre a ecologia desse grupo. O objetivo do estudo foi caracterizar a fauna de Oligochaeta em três córregos urbanos e um córrego rural, localizados na região central do Estado de São Paulo, sendo estes o córrego do Pinheirinho, Água Branca, rio Monjolinho e o córrego do Gouveia, respectivamente. Amostras do sedimento foram obtidas com um pegador Van Veen em duas áreas, durante o verão e inverno de 2001, em cada um dos ambientes estudados. Em todas as áreas de coletas foram tomadas medidas de pH, condutividade elétrica, oxigênio dissolvido e turbidez da água com o aparelho U-10 Horiba. A análise de componentes principais mostrou que os eixos I e II explicaram 68,18% da variabilidade dos resultados, sendo que, o primeiro eixo foi predominantemente explicado pelas variáveis granulométricas e o segundo eixo pelas variáveis limnológicas. A análise de agrupamento indicou que a área II do rio Monjolinho diferiu dos demais pontos de coleta. No presente estudo, o grupo Oligochaeta foi representado pelas famílias Tubificidae, Naididae, Alluroididae, Narapidae e Enchytraeidae. Entre as três espécies de Tubificidae, Limnodrilus hoffmeisteri Claparede, 1862 foi a mais abundante e mais freqüente. Os resultados forneceram informações importantes sobre a ecologia e distribuição de Oligochaeta límnicos.

Despite the importance of Oligochaeta to the dynamics of aquatic ecosystems and to studies of the biology of pollution, there is currently a dearth of information on this group's ecology in Brazil. The aim of this study was to describe the Oligochaeta fauna in four watercourses - three urban and one rural - in the state of São Paulo: the Pinheirinho stream, the Água Branca stream, the Monjolinho River and the Gouveia stream, respectively. Sediment samples were taken with a Van Veen grab in two areas from each watercourse, during the summer and winter of 2001. In all collection areas, measurements of the pH, electrical conductivity, dissolved oxygen and turbidity of the water were made with a Horiba U-10 device. Principal component analysis showed that axes 1 and 2 explained 68.18% of the results' variability, with the first axis predominantly associated with the granulometric data and the second one with the limnological data. Cluster analysis indicated that area II of the Monjolinho River differed from the other collection sites. In the present study, the Oligochaeta group was represented by Tubificidae, Naididae, Alluroididae, Narapidae and Enchytraeidae. Among the three species of Tubificidae, Limnodrilus hoffmeisteri Claparede, 1862, was the most abundant and most frequent species. The results provided important information on the ecology and distribution of limnic Oligochaeta.

The aim of this study is to assess the effects of industrial and sewage discharges on the benthic structure of urban rivers. Also, the species assemblages associated to different water quality conditions were studied. Four sampling sites were analyzed, from July 2000 to February 2002, during high water level in two urban rivers. In order to determine the quality of the water and the species assemblages, ANOVA, principal components analysis, species diversity and distance index among sites were applied. Eighty-five species or morphospecies were identified, dominated by Oligochaeta and Chironomidae. Average density of benthic invertebrates varied between 233 ind/m² and 29265 ind/m², with higher densities registered in the reference sampling site than in the ones affected by industrial discharges. The species richness ranged from four to 43 taxa, and the Shannon-Wiener index, from 1.37 to 3.95, with the highest value registered in Saucesito river. Filtering and gathering collectors were the dominant feeding groups in all the sites because of the high fine particulate organic matter content. The biological oxygen demand was the main factor in determinating the benthic invertebrates distribution and composition. Las Tunas River is hardly polluted, with low benthic density, species richness and diversity, and high DBO5 values. Saucesito River shows a better water quality, mainly upstream of the industrial discharges. The gradient from clean to polluted water quality, was characterized by the species assemblages Ostracods Podocopida, Tanytarsus sp., D. (D.) obtusa, Djalmabatista sp. 2, Rheotanytarsus sp. 1, S. fossularis and Cricotopus sp. 1 → N. variabilis, C. xanthus and L. hoffmeisteri.

Se estudió la incidencia de los efluentes industriales y cloacales sobre la estructura del bentos en el río Las Tunas y su afluente Saucesito (Paraná, Provincia de Entre Ríos, Argentina). Se determinaron las especies y asociaciones de especies en gradientes de buena a mala calidad del agua de estos ríos urbanos. Se realizaron cuatro muestreos, entre julio de 2000 y febrero de 2002, en cuatro estaciones a lo largo del curso. Los resultados obtenidos revelaron que, tanto la densidad como la diversidad específica fueron influenciadas por la contaminación orgánica, con una disminución brusca en la estación afectada por el vertido de los efluentes del parque industrial. Se registraron 85 taxa, siendo los oligoquetos y quironómidos los dominantes. Del análisis de componentes principales, se infirió que la demanda biológica de oxígeno fue el factor que más incidió en la distribución y composición de organismos bentónicos. El río Las Tunas presentó altos valores de DBO5, la menor densidad, riqueza y diversidad específica, sin recuperación de la calidad del agua en todo el tramo. Aguas arriba, el río Saucesito presentó una mejor calidad, principalmente en la estación de referencia ubicada antes del parque industrial.

Se analizó la estructura del bentos de ambientes lóticos afectados por la construcción de puentes y carreteras sobre el delta del río Paraná. El objetivo del estudio fue determinar el grado de impacto de los disturbios físicos provocados por la construcción de la obra sobre los invertebrados bentónicos de cuatro cauces secundarios del río Paraná Inferior, los ríos Carbón Chico, Carbón Grande 1, Carbón Grande 2 y Paranacito Victoria. El análisis de cluster y el DCA delimitaron dos grupos de hábitats de acuerdo al tamaño de grano de los sedimentos y contendido de materia orgánica. Un grupo estuvo formado por estaciones con sedimentos limo-arcilloso, principalmente aguas arriba de los puentes, y mostró mayor riqueza de especies, diversidad y biomasa que el otro grupo, integrado por estaciones con sedimento arenoso, debajo y aguas abajo de los puentes, donde se obtuvieron las mayores densidades alcanzadas por Narapa bonettoi y Myoretronectes paranaensis. A pesar que la construcción de los puentes afectó la estructura bentónica debido a los procesos de erosión de los sedimentos de fondo, la asociación faunística típica de fondos arenosos y móviles del río Paraná colonizó exitosamente los hábitats a menos de un año de los disturbios provocados por la construcción de la obra.

Benthic assessment of lotic environments affected by bridge and highway construction at the Paraná River Delta is reported. The purpose of the study was to examine the degree of impact of physical disturbances on benthic invertebrates in four secondary channels, Carbón Chico, Carbón Grande 1, Carbón Grande 2 and Paranacito Victoria rivers. Cluster and DCA analyses showed two groups of habitats based on the grain size sediments and organic matter content. The sites with silt-clayed sediments, mainly upstream from the bridges, showed higher species richness, diversity and benthic biomass than the sites with sandy sediments, under and downstream from the bridges, where the highest densities reached by Narapa bonettoi and Myoretronectes paranaensis were observed. Although the bridge construction has affected the benthic structure due to the erosion process of bottom sediments, the typical r-strategist species assemblage related to sandy unstable sediments in the Paraná River colonized the habitat successfully within less than one year from the disturbances.

Analisou-se a estrutura de bentos de ambientes lóticos afetados pela construção de pontes e estradas sobre o delta do rio Paraná. O objetivo do estudo foi determinar o grau de impacto dos distúrbios físicos provocados pela construção da obra sobre os invertebrados bentônicos de quatro leitos secundários do rio Paraná Inferior, os rios "Carbón Chico", "Carbón Grande 1", "Carbón Grande 2" e "Paranacito Victoria". A análise de cluster e o DCA delimitaram dois grupos de habitat de acordo ao tamanho do grão dos sedimentos e conteúdo de matéria orgânica. Um grupo esteve formado por estações com sedimentos limo-argiloso, principalmente águas acima das pontes, e mostrou maior riqueza de espécies, diversidade e biomassa que o outro grupo, integrado por estações com sedimento arenoso, sob e águas abaixo das pontes, onde se obtiveram as maiores densidades alcançadas por Narapa bonettoi e Myoretronectes paranaensis. Apesar de que a construção das pontes afetou a estrutura bentônica devido aos processos de erosão dos sedimentos de fundo, a associação faunística típica de fundos arenosos e móveis do rio Paraná colonizou, com sucesso, os habitats a menos de um ano dos distúrbios provocados pela construção da obra.

A riqueza de espécies de Oligochaeta foi investigada em duas represas construídas no curso do rio Tietê. Em cada represa foram obtidas 360 amostras de sedimento em 90 pontos de amostragem, utilizando-se uma draga Van Veen (378cm²), nos meses de janeiro, abril, julho e outubro de 2001. No total foram examinados 12.826 exemplares de oligoquetos pertencentes a 20 espécies, 10 gêneros e 4 famílias. Naididae e Dero foram a família e o gênero com maiores riquezas de espécies, com 14 e 9 espécies, respectivamente. Do total de espécies identificadas, 6 estiveram presentes em ambas represas, sendo Branchiura sowerbyi (Tubificidae) a espécie mais abundante nestes ambientes. A análise das amostras revelou que a maioria das espécies de oligoquetos é rara e de freqüência de ocorrência acidental, evidenciando que para um melhor conhecimento da riqueza de espécies é realmente necessário um grande esforço amostral, com elevado número de pontos de amostragem.

The species richness of Oligochaeta was evaluated in two reservoirs belonging to Tietê River system, Bariri and Ponte Nova Reservoirs. 360 sediment samples were taken in each reservoir at 90 sampling stations using a Van Veen grab (378cm²), in the months January, April, July and October 2001. A total of 12.826 oligochaete specimens were collected, belonging to 20 species, 10 genera and 4 families. The family and genus with the highest species richness were Naididae and Dero, with 14 and 9 species, respectively. Among all species identified 6 occurred in both reservoirs, being Branchiura sowerbyi (Tubificidae) the most abundant species in them. The study also revealed that most Oligochaeta species are rare and have accidental occurrence, thus evidencing that for a better knowledge of species richness is actually necessary a great sampling effort including a large number of sampling points.