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Microplastic (MP) is yet another form of chronic anthropogenic contribution to the environment. MPs are plastic particles (<5 mm) that have been widely found in the most diverse natural environments, but their real impacts on ecosystems are still under investigation. Here, we studied the toxicity of naturally aged secondary polypropylene (PP) MPs after constant exposure to ultraviolet radiation (26 µm) to the third instar larvae of Chironomus sancticaroli, a dipteran species. The concentrations tested were 13.5; 67.5; and 135 items g-1 of dry sediment. C. sancticaroli organisms were investigated for fragment ingestion, mortality and changes in enzymatic biomarkers after 144 h of exposure. The organisms were able to ingest MPs from the first 48 h, and the amount of items internalized was dose-dependent and time-dependent. Overall, the results show that mortality was low, being significant at the lowest and highest concentrations (13.5 and 135 items g-1). Regarding changes in biochemical markers, after 144 h MDA and CAT activities were both significantly altered (increased and reduced, respectively), while SOD and GST levels were unchanged. In the present study, naturally aged polypropylene MPs induced biochemical toxicity in C. sancticaroli larvae, with toxicity being higher according to exposure time and particle concentration.

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BACKGROUND: Freshwater organisms are facing increasing salinity levels, not only due to natural environmental processes, but also human activities, which can cause several physiological adaptations to osmotic stress. Additionally, these organisms might also have to deal with contamination by microbial insecticides. Our main goal was to use Chironomus xanthus to assess the chronic effects of increasing the salinity and commercial formulations of the microbial insecticides based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) as active ingredients, respectively. RESULTS: A significant interaction of growth was observed between the biopesticide based on Bb and NaCl on the larvae of C. xanthus. Single exposure to NaCl and each one of the formulations demonstrated deleterious impacts not only on larval development, but also on the emergence success and emergence time of this nontarget insect, with potential consequences for freshwater ecosystems due to cascading effects. CONCLUSION: The chronic effects induced by both bioinsecticides show that these formulations can have environmental impacts on nontarget freshwater insects. © 2023 Society of Chemical Industry.

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The functional traits of species respond to environmental gradient changes, which, in turn, are responsible for the niche specialization of species. We analyzed the niche specialization of several Tanypodinae taxa (predatory non-biting midge, 4th instar, n = 693) along the depth zones of the water in six shallow tropical reservoirs. We measured the body length and diet composition of seven Tanypodinae larvae genus. Community-weighted mean (CWM) traits index was utilized to calculate the niche distribution of body length and diet composition. We analyzed the niche distribution of predator larvae, through a simple linear analysis of CWM index and the depth of the water, and by establishing correlations between body length and diet composition. In our study, it was found that the consumption of oligochaete (b = 0.30, SE ± 0.04, t = 7.02, p = 0.0001, R2 = 0.45) and the body length (b = 0.64, SE ± 0.11, t = 5.44, p = 0.0001, R2 = 0.33) increased in deeper zones. We observed a strong and positive relationship between oligochaete consumption and a longer body (r = 0.91, p = 0.0001). We inferred that changes in habitat characteristics, from littoral to deeper zones of the reservoirs, are expected to have influenced the selection of larvae traits predators. We concluded that body length determines the diet consumption and accurately reflects the niche distribution of Tanypodinae assemblages. The functional trait approach proved to be an efficient tool for the analysis of the ecological processes that determine the structure of a non-biting midge predator assemblage.

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The diet of shredder chironomid larvae depends on the local and temporal conditions of the food resources. We analysed the gut content of shredder chironomid larvae that colonised the leaf litter of three riparian species: Hedychium coronarium, Pteridium arachnoideum and Magnolia ovata. We hypothesised that the differences in the decomposition rates of leaf litter species influence the consumption of plant tissue by shredder chironomid taxa over time. We incubated perforated bottles with each leaf species within four low-order streams during 1st, 3rd, 7th, 22nd, 36th, 55th and 85th day of exposure. We used an analysis of covariance (ANCOVA) to compare differences in the percentage of AFDM (ash-free dry mass) and AOM (amorphous organic matter) among leaf litter species. To verify differences in the larvae abundance, we used a general linear model, and to test if there were feeding preferences for AFDM and AOM, we used the adapted Paloheimo selectivity index. Magnolia ovata presented a higher quantity of AOM followed by H. coronarium and P. arachnoideum. Pteridium arachnoideum showed a higher AFDM followed by H. coronarium and M. ovata. The larvae abundance was different among plant species and varied significantly with AFDM and AOM quantities. The consumption of plant tissue by shredder chironomid differed temporarily and among riparian species, where facultative or strict shredders showed strong association with different leaf litter species. The amount of AFDM and AOM in plant tissues explained these differences. We highlighted that shredder chironomids displayed an important role as co-participants in the decomposition process.

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Although epibiont ciliates make up a significant part of the biomass in aquatic ecosystems and may cause perceptible alterations in the population dynamics of their hosts, studies on the extrinsic and intrinsic factors that control the abundance of these microorganisms are scarce in literature. In the present study, we investigated the colonization site and intensity of rhabdostylid epibiont upon chironomid larvae and assessed the influence of organic pollution and chironomid communities on the prevalence and abundance of epibiont ciliates at five sampling stations (two in rural areas and three in urban areas) along a neotropical urban stream over a period of 12 months. Among the 24 genera of chironomids found and the 31,976 larvae analyzed, 96.12% belonged to the Chironomus genus, of which 16.95% (5212) were colonized by Rhabdostyla aff. chironomi. The infestation intensity varied from one to 67 individuals per host with an average intensity of 4.86 (± 33.45). Ciliates were only found colonizing the chironomids' ventral tubules. The high number of chironomid larvae, high host- and site-specificity, low infestation intensity, and absence of apparent structural damage to hosts evidence an intimate relationship between epibiont and basibiont as well as a possibly long coevolutionary history. Both prevalence and abundance of epibiont ciliates were correlated to the pollution rate of the studied stream. There was an alteration in the composition and structure of the chironomid community along the sampling stations. Numeric dominance of Chironomus-tolerant chironomids and its direct correlation to infestation prevalence and to ciliates abundance highlights the predilection of both peritrich ciliates and Chironomus larvae for organically-enriched environments.

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Abstract The family Chironomidae (Diptera) is the most widely distributed, most diverse, and often the most abundant of all families of benthic macroinvertebrates in aquatic ecosystems, including estuaries and other coastal marine ecosystems. Chironomid assemblages are likely to provide a useful measure of biotic integrity in estuaries of Costa Rica, which lack an intensive estuarine bioassessment tool to support environmental monitoring and regulatory programs. We characterized the taxonomic composition of Chironomidae, tested a Chironomidae Index of Biotic Integrity (CIBI) developed from extrinsic pollution tolerance values for its efficacy in evaluating the surface water quality and physical habitat, and made recommendations for increasing the sensitivity of the CIBI to detect differing degrees of stress across a range of estuaries in Costa Rica. Specifically, we selected nine estuaries within six different watersheds across a land use gradient located on the Caribbean coast of Costa Rica and collected Chironomidae surface-floating pupal exuviae (SFPE) samples biannually for two consecutive years (July 2012, Jan. 2013, July 2013, Jan. 2014). We identified 228 morphospecies and 70 genera from 17 071 Chironomidae pupal exuviae collected from nine estuaries, which ranked in the following order from lowest to highest biotic integrity based on CIBI scores: Estero Negro, Laguna Cuatro, Laguna Jalova, Laguna del Tortuguero, Río Parismina, Laguna Barra del Colorado, Río Pacuare, Río Bananito, and Río Estrella. The CIBI successfully differentiated between estuaries with poor versus good biotic integrity, indicating that CIBI could be used to evaluate the surface water quality and physical habitat of Costa Rican estuaries. We recommend that future studies refine our approach by developing regionally accurate genus and corresponding species-level tolerance values to improve the sensitivity of the CIBI for biological monitoring of Costa Rican estuaries. Rev. Biol. Trop. 66(3): 1118-1134. Epub 2018 September 01.

Resumen La familia Chironomidae (Diptera) es la más ampliamente distribuida, más diversa y a menudo, la más abundante de todas las familias de macroinvertebrados bentónicos en ecosistemas acuáticos, incluyendo estuarios y otros ecosistemas marinos. Probablemente, los ensambles de quironómidos proporcionen una medida útil de integridad biótica en estuarios de Costa Rica, los cuales carecen de una herramienta de evaluación biológica que respalde programas de monitoreo ambiental y programas regulatorios. Caracterizamos la composición taxonómica de Chironomidae, probamos un Índice de Integridad Biótica de Chironomidae (CIBI) desarrollado a partir de valores de tolerancia de contaminación extrínseca, por su eficacia en evaluar la calidad de la superficie del agua y el hábitat físico. Además, realizamos recomendaciones para incrementar la sensibilidad del CIBI para detectar diferentes grados de estrés en un rango de estuarios en Costa Rica. Específicamente, seleccionamos nueve estuarios dentro de seis cuencas diferentes a lo largo de un gradiente de uso de suelo en la costa Caribe de Costa Rica y recolectamos muestras de las exuvias pupales que flotan en la superficie (SFPE) por dos años consecutivos (Julio 2012, Enero 2013, Julio 2013, Enero 2014). Identificamos 228 morfoespecies y 70 géneros de 17 071 exuvias de pupas de Chironomidae recolectadas en nueve estuarios, los cuales se clasificaron en el siguiente orden de menor a mayor integridad biótica basado en los valores del CIBI: Estero Negro, Laguna Cuatro, Laguna Jalova, Laguna del Tortuguero, Río Parismina, Laguna Barra del Colorado, Río Pacuare, Río Bananito, y Río Estrella. El CIBI diferenció eficazmente entre estuarios con integridad biótica pobre versus buena, indicando que el CIBI puede ser usado para evaluar la calidad de la superficie del agua y el hábitat físico de estuarios de Costa Rica. Recomendamos que estudios futuros refinen nuestro planteamiento desarrollando valores de tolerancia de géneros precisos regionalmente y niveles correspondientes de especies para mejorar la sensibilidad del CIBI para el monitoreo de estuarios de Costa Rica.

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The aim of this study was to develop a statistical model to assess the environmental quality of reservoirs located in semi-arid region using metrics of anthropogenic disturbance, water quality variables, and benthic macroinvertebrate communities as indicators. The proposed model was applied to 60 sites located in three reservoirs in the Paraíba river basin, Brazilian semi-arid region. Collections were made in December 2011. In each site, we collected one sample of benthic macroinvertebrates and one water sample for the determination of physical and chemical parameters. Characterization of the landscape was made through application of 10 physical habitat protocols on each site for the collected information on disturbance and subsequent calculation of disturbance metrics. The results showed the formation of two groups: group 1, consisting of 16 minimally altered sites, and group 2, with 44 severely altered sites. The proposed statistical model was sensitive enough to detect changes. In the minimally altered group, the Chironomids Aedokritus and Fissimentum were dominant, indicating a higher environmental quality, while Coelotanypus and Chironomus were abundant in severely altered sites with lower environmental quality. The conservation and management of reservoirs in semi-arid regions should be intensified in view of the need to maintain the environmental quality of these ecosystems.

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This large family is poorly known in Colombia, where only 44 species have been recorded in 20 genera. All of them are included in Cecidomyiinae, which is the most diverse subfamily of gall midges in number of species and feeding habits, including phytophagous, predaceous and fungivorous species. Most of them are galler. The other subfamilies have never been recorded in this country.

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Only 30 chironomid species distributed in 16 genera and three subfamilies are formally recorded to Colombia. Another 32 genera and two subfamilies have been recorded on larval stage, with no identification at species level. Many new records, genera and species are expected when focusing on systematics of chironomids from Colombia.

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Ecological studies on food webs have considerably increased in recent decades, especially in aquatic communities. Because Chironomidae family are highly specious, occurring in almost all aquatic habitats is considered organisms-key to initiate studies on ecological relationships and trophic webs. We tested the hypothesis that the diversity of the morphospecies diet reflects differences on both the food items available among habitats and the preferences of larval feeding. We analyzed the gut content of the seven most abundant Chironomidae morphospecies of the different habitats from the Upper Paraná River. We categorized the food items found into algae, fungal spores, fragments of plants, algae and animal fragments and sponge spicules. We observed the algae predominance in the gut content of morphospecies from lakes. Considering the different regions from each lake, we registered the highest food abundance in the littoral regions in relation to the central regions. From the variety of feeding habits (number of item kinds), we classified Chironomus strenzkei, Tanytarsus sp.1, Procladius sp.1 as generalist morphospecies. We found a nested pattern between food items and Chironomidae morphospecies, where some items were common to all taxa (e.g., Bacillariophyceae algae, especially), while others were found in specific morphospecies (e.g., animals fragments found in Procladius sp.1). The algae represented the most percentage of gut contents of Chironomidae larvae. This was especially true for the individuals from littoral regions, which is probably due to the major densities of algae associated to macrophytes, which are abundant in these regions. Therefore, the feeding behavior of these morphospecies was generalist and not selective, depending only of the available resources.

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Abstract Ecological studies on food webs have considerably increased in recent decades, especially in aquatic communities. Because Chironomidae family are highly specious, occurring in almost all aquatic habitats is considered organisms-key to initiate studies on ecological relationships and trophic webs. We tested the hypothesis that the diversity of the morphospecies diet reflects differences on both the food items available among habitats and the preferences of larval feeding. We analyzed the gut content of the seven most abundant Chironomidae morphospecies of the different habitats from the Upper Paraná River. We categorized the food items found into algae, fungal spores, fragments of plants, algae and animal fragments and sponge spicules. We observed the algae predominance in the gut content of morphospecies from lakes. Considering the different regions from each lake, we registered the highest food abundance in the littoral regions in relation to the central regions. From the variety of feeding habits (number of item kinds), we classified Chironomus strenzkei, Tanytarsus sp.1, Procladius sp.1 as generalist morphospecies. We found a nested pattern between food items and Chironomidae morphospecies, where some items were common to all taxa (e.g., Bacillariophyceae algae, especially), while others were found in specific morphospecies (e.g., animals fragments found in Procladius sp.1). The algae represented the most percentage of gut contents of Chironomidae larvae. This was especially true for the individuals from littoral regions, which is probably due to the major densities of algae associated to macrophytes, which are abundant in these regions. Therefore, the feeding behavior of these morphospecies was generalist and not selective, depending only of the available resources.

Resumo Estudos sobre redes alimentares têm aumentado consideravelmente nas últimas décadas em pesquisas de ecologia, principalmente em comunidades aquáticas. Em função Família Chironomidae ser altamente especiosa, ocorrendo em quase todos os hábitats aquáticos, é considerada como organismos-chave para estudos preliminares sobre as relações ecológicas como redes tróficas. Nós testamos a hipótese de que a diversidade de dietas das morfoespécies reflete diferenças tanto na disponibilidade dos itens alimentares entre os hábitats analisados, quanto preferencias alimentares das larvas. Nós analisamos o conteúdo digestivo das sete morfoespécies mais abundantes de diferentes habitats da planície de inundação do alto rio Paraná. Nós categorizamos os itens alimentares encontrados como algas, esporos de fungos, fragmentos vegetais, fragmentos de algas ou de animais e espículas de esponjas. Nós observamos a predominância de algas no conteúdo digestivo das morfoespécies lacustres. Considerando as diferentes regiões de cada lagoa, nós registramos as maiores abundâncias de alimentos nas regiões litorâneas, quando comparadas com as regiões centrais. A partir da variedade de hábitos alimentares (número de tipos de itens), classificamos Chironomus strenzkei, Tanytarsus sp.1 e Procladius sp.1 como morfoespécies generalistas. Nós encontramos um padrão aninhado entre os itens alimentares e as morfoespécies de Chironomidae, onde alguns itens foram comuns a todos os táxons (por exemplo, algas da Classe Bacillariophyceae), enquanto outros foram encontrados em morfoespécies mais especificas (por exemplo, fragmentos de animais encontrados em Procladius sp.1). As algas representaram a maior porcentagem do conteúdo digestivo das larvas de Chironomidae. Este fato foi especialmente verdadeiro para os indivíduos das regiões litorâneas, o qual é devido, provavelmente, pelas maiores densidades de algas associadas à macrófitas, que são abundantes nessas regiões. Portanto, o comportamento alimentar dessas morfoespécies foi generalista e não seletivo, dependendo apenas dos recursos disponíveis.

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Clinodiplosis bellum sp. nov. associated with Diplopterys pubipetala (A.Juss.) Anderson and Davis (Malpighiaceae) from Brazil are described. This is the first species of Clinodiplosis described to State of São Paulo and the first formal description of Diplopterys pubipetala (Malpighiaceae) as host plant of Cecidomyiidae species. Description and illustration of the Clinodiplosis bellum sp. nov. (Diptera: Cecidomyiidae) are given.

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Clinodiplosis bellum sp. nov. associated with Diplopterys pubipetala (A.Juss.) Anderson and Davis (Malpighiaceae) from Brazil are described. This is the first species of Clinodiplosis described to State of São Paulo and the first formal description of Diplopterys pubipetala (Malpighiaceae) as host plant of Cecidomyiidae species. Description and illustration of the Clinodiplosis bellum sp. nov. (Diptera: Cecidomyiidae) are given.

Clinodiplosis bellum sp. nov. associada a Diplopterys pubipetala (A.Juss.) Anderson and Davis (Malpighiaceae) do Brasil é descrita. Esta é a primeira espécie de Clinodiplosis descrita para o Estado de São Paulo e a primeira descrição formal de Diplopterys pubipetala (Malpighiaceae) como planta hospedeira de uma espécie de Cecidomyiidae. Descrição e ilustrações de Clinodiplosis bellum sp. nov. (Diptera: Cecidomyiidae) são apresentadas.

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Clinodiplosis bellum sp. nov. associated with Diplopterys pubipetala (A.Juss.) Anderson and Davis (Malpighiaceae) from Brazil are described. This is the first species of Clinodiplosis described to State of São Paulo and the first formal description of Diplopterys pubipetala (Malpighiaceae) as host plant of Cecidomyiidae species. Description and illustration of the Clinodiplosis bellum sp. nov. (Diptera: Cecidomyiidae) are given.(AU)

Clinodiplosis bellum sp. nov. associada a Diplopterys pubipetala (A.Juss.) Anderson and Davis (Malpighiaceae) do Brasil é descrita. Esta é a primeira espécie de Clinodiplosis descrita para o Estado de São Paulo e a primeira descrição formal de Diplopterys pubipetala (Malpighiaceae) como planta hospedeira de uma espécie de Cecidomyiidae. Descrição e ilustrações de Clinodiplosis bellum sp. nov. (Diptera: Cecidomyiidae) são apresentadas.(AU)

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The niche overlap between trophic groups of Chironomidae larvae in different habitats was observed between trophic groups and between different environments in Neotropical floodplain. For the evaluation we used the index of niche overlap (CXY) and analysis of trophic networks, both from the types and amount of food items identified in the larval alimentary canal. In all environments, the larvae fed on mainly organic matter such as plants fragments and algae, but there were many omnivore larvae. Species that have high values of food items occurred in diverse environments as generalists with great overlap niche and those with a low amount of food items with less overlap niche were classified as specialists. The largest number of trophic niche overlap was observed among collector-gatherers in connected floodplain lakes. The lower values of index niche overlap were predators. The similarity in the diet of different taxa in the same niche does not necessarily imply competition between them, but coexistence when the food resource is not scarce in the environment even in partially overlapping niches.

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Benthic habitats are linked by physical processes and are essential elements in assessing of the distribution dynamics of Chironomidae dipteran insects and their role in aquatic ecosystems. This work presents results of distribution patterns of chironomids larvae in 38 sites that are abundant in the study site, inhabiting the substrate of the main river channel, rapids, tributary brook, floodplain lakes and reservoir along the Sepotuba River from its mouth at the Paraguay River to the headwater region. A total of 1,247 larvae was registered. The most abundant taxa were Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) and Tanytarsus sp. (15.0%). Fissimentum desiccatum were found only in the reservoir; Fissimentum sp.2 and Tanytarsus cf. T. obiriciae sp.2 in floodplain lakes, and Goeldichironomus sp. in the main channel. The low diversity of the sites S06 and S35 is caused by the near-exclusive presence of the species Cricotopus sp.3, alone or together with one or another taxon (Tanytarsus sp., Djalmabatista sp.3). Collectors-filterers represent 16%, collectors-gatherers 15%, predators 11% and scrapers only 1%. The predators dominated in the secondary channel (±88 ind/m2), corresponding to 40% of the total of this group. Cryptochironomus sp.2 (34%) and Ablasbemyia gr. annulata (26%) were the most abundant among the predators. The differences along the river course are decisive for the formation of distinct or discontinuous communities and the limits become obvious though the interrelations between the populations in the community, as for instance, competition for food and habitats.

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Considering the importance of benthic macroinvertebrates for diagnosis of variations in the ecological conditions of aquatic habitats, the aim of this study was to investigate the structure of the Chironomidae and Oligochaeta assemblages along an organic pollution gradient. The fauna specimens were obtained with the use of artificial substrates, and the environmental variables were recorded at five sites of the São Lourenço River, during 12 months. Metrics of the assemblage and detrended correspondence analysis were used to verify the response of the fauna to the pollution gradient. Procrustes analysis was used to verify whether the data on the Chironomidae and Oligochaeta assemblages, as well as the taxonomic and numerical resolution of these groups, provide similar results in relation to the pollution gradient. The richness, evenness, and taxonomic composition of the Chironomidae and Oligochaeta assemblages varied significantly among the collection sites, with distinct conservation conditions. Genera of the subfamilies Orthocladiinae and Tanypodinae were associated with the sites upstream of the urban area, where the dissolved oxygen levels are higher. Species of Oligochaeta and the genus Chironomus were associated with more organically polluted sites. No concordance was observed in the response of the Chironomidae and Oligochaeta assemblages in relation to the environmental variables, indicating the need to use both groups in biomonitoring studies. On the other hand, both the data on composition (presence or absence) and those on the lowest taxonomic resolution (abundance of subfamilies) were effective to diagnose the pollution gradient in the river studied. Therefore, when the environmental conditions along a river's gradient are contrasting, we suggest the use of the lowest taxonomic resolution of Chironomidae and Oligochaeta in biomonitoring. That procedure considerably reduces the assessment time, besides being a method that can be used by people not specializing in the taxonomy of groups.

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The niche overlap between trophic groups of Chironomidae larvae in different habitats was observed between trophic groups and between different environments in Neotropical floodplain. For the evaluation we used the index of niche overlap (CXY) and analysis of trophic networks, both from the types and amount of food items identified in the larval alimentary canal. In all environments, the larvae fed on mainly organic matter such as plants fragments and algae, but there were many omnivore larvae. Species that have high values of food items occurred in diverse environments as generalists with great overlap niche and those with a low amount of food items with less overlap niche were classified as specialists. The largest number of trophic niche overlap was observed among collector-gatherers in connected floodplain lakes. The lower values of index niche overlap were predators. The similarity in the diet of different taxa in the same niche does not necessarily imply competition between them, but coexistence when the food resource is not scarce in the environment even in partially overlapping niches.

A sobreposição de nichos entre grupos tróficos de larvas de Chironomidae em diferentes tipos de ambientes foi verificada entre os grupos tróficos e entre diferentes ambientes em uma planície de inundação Neotropical. Para a avaliação foi utilizado o Índice de Sobreposição de Nicho (CXY) e análises de redes tróficas, ambos a partir dos tipos e quantidade de itens alimentares identificados no tubo digestivo das larvas. As larvas alimentaram-se em todos os ambientes principalmente de detritos orgânicos como os fragmentos de plantas e algas, porém, verificou-se alto nível de omnívora. As espécies que tem altos valores de itens alimentares ocorreram em diversos ambientes como generalistas e com grande sobreposição de nichos e aqueles com baixos itens alimentares e com menor sobreposição foram classificados como especialistas. O maior número de sobreposição de nichos tróficos foi verificado em coletores-catadores nas lagoas com conexão. Os menores valores do índice foram verificados nos predadores. A semelhança na dieta de diferentes táxons e grupos tróficos em um mesmo nicho não implica, necessariamente, uma competição entre eles, porém uma coexistência quando o recurso alimentar não é escasso no ambiente, mesmo com sobreposição parcial de nichos.

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Benthic habitats are linked by physical processes and are essential elements in assessing of the distribution dynamics of Chironomidae dipteran insects and their role in aquatic ecosystems. This work presents results of distribution patterns of chironomids larvae in 38 sites that are abundant in the study site, inhabiting the substrate of the main river channel, rapids, tributary brook, floodplain lakes and reservoir along the Sepotuba River from its mouth at the Paraguay River to the headwater region. A total of 1,247 larvae was registered. The most abundant taxa were Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) and Tanytarsus sp. (15.0%). Fissimentum desiccatum were found only in the reservoir; Fissimentum sp.2 and Tanytarsus cf. T. obiriciae sp.2 in floodplain lakes, and Goeldichironomus sp. in the main channel. The low diversity of the sites S06 and S35 is caused by the near-exclusive presence of the species Cricotopus sp.3, alone or together with one or another taxon (Tanytarsus sp., Djalmabatista sp.3). Collectors-filterers represent 16%, collectors-gatherers 15%, predators 11% and scrapers only 1%. The predators dominated in the secondary channel (±88 ind/m2), corresponding to 40% of the total of this group. Cryptochironomus sp.2 (34%) and Ablasbemyia gr. annulata (26%) were the most abundant among the predators. The differences along the river course are decisive for the formation of distinct or discontinuous communities and the limits become obvious though the interrelations between the populations in the community, as for instance, competition for food and habitats.

Hábitats bênticos estão ligados por processos físicos e são elementos essenciais na avaliação da dinâmica de distribuição de insetos dípteros Chironomidae e seu papel em ecossistemas aquáticos. Este trabalho apresenta os resultados dos padrões de distribuição de larvas de Chironomidae em 38 locais que são abundantes na área de estudo, habitando o substrato do canal principal do rio, cachoeiras, córregos tributários, lagoas de planície de inundação, e reservatórios ao longo do Rio Sepotuba de sua desembocadura ao Rio Paraguai e na região de cabeceira. Um total de 1,247 larvas foi registrada. O táxons mais abundantes foram Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) e Tanytarsus sp. (15.0%). Fissimentum desiccatum foi encontrado somente no reservatório; Fissimentum sp.2 e Tanytarsus cf. T. obiriciae sp.2 nas lagoas de planície de inundação, e Goeldichironomus sp. no canal principal. A baixa diversidade dos locais S06 e S35 foi causada pela exclusiva presença da espécie Cricotopus sp.3, sozinha ou junta com um ou outro táxon (Tanytarsus sp., Djalmabatista sp.3). Coletores-filtradores representaram 16%, coletores-catadores 15%, predadores 11% e raspadores somente 1%. Os predadores dominaram no canal secundário (±88 ind/m2), correspondendo a 40% do total deste grupo. Cryptochironomus sp.2 (34%) e Ablasbemyia gr. annulata (26%) foram os mais abundantes entre os predadores. As diferenças ao longo do curso do rio foram decisivas para a formação de comunidades distintas e descontínuas e os limites tornam óbvios pertinentes às interrelações entre as populações na comunidade, como por exemplo, competição por alimento e hábitat.

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Benthic habitats are linked by physical processes and are essential elements in assessing of the distribution dynamics of Chironomidae dipteran insects and their role in aquatic ecosystems. This work presents results of distribution patterns of chironomids larvae in 38 sites that are abundant in the study site, inhabiting the substrate of the main river channel, rapids, tributary brook, floodplain lakes and reservoir along the Sepotuba River from its mouth at the Paraguay River to the headwater region. A total of 1,247 larvae was registered. The most abundant taxa were Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) and Tanytarsus sp. (15.0%). Fissimentum desiccatum were found only in the reservoir; Fissimentum sp.2 and Tanytarsus cf. T. obiriciae sp.2 in floodplain lakes, and Goeldichironomus sp. in the main channel. The low diversity of the sites S06 and S35 is caused by the near-exclusive presence of the species Cricotopus sp.3, alone or together with one or another taxon (Tanytarsus sp., Djalmabatista sp.3). Collectors-filterers represent 16%, collectors-gatherers 15%, predators 11% and scrapers only 1%. The predators dominated in the secondary channel (±88 ind/m2), corresponding to 40% of the total of this group. Cryptochironomus sp.2 (34%) and Ablasbemyia gr. annulata (26%) were the most abundant among the predators. The differences along the river course are decisive for the formation of distinct or discontinuous communities and the limits become obvious though the interrelations between the populations in the community, as for instance, competition for food and habitats.(AU)

Hábitats bênticos estão ligados por processos físicos e são elementos essenciais na avaliação da dinâmica de distribuição de insetos dípteros Chironomidae e seu papel em ecossistemas aquáticos. Este trabalho apresenta os resultados dos padrões de distribuição de larvas de Chironomidae em 38 locais que são abundantes na área de estudo, habitando o substrato do canal principal do rio, cachoeiras, córregos tributários, lagoas de planície de inundação, e reservatórios ao longo do Rio Sepotuba de sua desembocadura ao Rio Paraguai e na região de cabeceira. Um total de 1,247 larvas foi registrada. O táxons mais abundantes foram Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) e Tanytarsus sp. (15.0%). Fissimentum desiccatum foi encontrado somente no reservatório; Fissimentum sp.2 e Tanytarsus cf. T. obiriciae sp.2 nas lagoas de planície de inundação, e Goeldichironomus sp. no canal principal. A baixa diversidade dos locais S06 e S35 foi causada pela exclusiva presença da espécie Cricotopus sp.3, sozinha ou junta com um ou outro táxon (Tanytarsus sp., Djalmabatista sp.3). Coletores-filtradores representaram 16%, coletores-catadores 15%, predadores 11% e raspadores somente 1%. Os predadores dominaram no canal secundário (±88 ind/m2), correspondendo a 40% do total deste grupo. Cryptochironomus sp.2 (34%) e Ablasbemyia gr. annulata (26%) foram os mais abundantes entre os predadores. As diferenças ao longo do curso do rio foram decisivas para a formação de comunidades distintas e descontínuas e os limites tornam óbvios pertinentes às interrelações entre as populações na comunidade, como por exemplo, competição por alimento e hábitat.(AU)

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