Aquatic Insect Herbivore Functional Community Traits Respond to a Different Niche Between a Riparian and Sugar Cane Leaf Litter Processing.

The niche of aquatic insect herbivores can be determined by the resource quality of leaf litter species. We compared the niche functional trait of aquatic insect herbivores between Magnolia ovata (riparian tree) and Saccharum officinarum (sugar cane) leaf litter processing. We hypothesized M. ovata and sugar cane leaf litter species would influence different functional traits niche of aquatic insect herbivores due to different quality resource leaves. We performed colonization experiments using dry leaves in five streams during 30-34 days. We utilized five replicates per leaf litter (n = 25) containing 12 g of dry leaves. We compared the niche specialization of herbivore functional traits using the Community Weight Mean (CWM) index and throughout herbivore abundance and the similarity composition of taxa. Additionally, we analysed the influence of organic matter in the CMW index of herbivore functional trait niche. We observed a higher abundance of shredders than scrapers in both leaf litter species. The M. ovata leaf litter selected a more specialized niche of respiration trait composed mainly chironomid shredder larvae, with the osmotic mechanism. The community structure differs weakly with a stronger and positive relationship between organic matter and respiration CWM index in riparian than sugar cane leaf litter. Concerning different composition communities between leaf plants, we consider that aquatic insect herbivore demonstrates a preference to leaf litter species with a specific resource. Additionally, most taxa adapt their feeding habit dependent on the availability of resource food.

Shredder Chironomid Diets Are Influenced by Decomposition Rates of Different Leaf Litter Species.

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.

Body Length Determines the Diet and Niche Specialization of Non-Biting Midge Predator (Tanypodinae) Larvae in Shallow Reservoirs.

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.

Aquatic insect community structure under the influence of small dams in a stream of the Mogi-Guaçu river basin, state of São Paulo.

The fragmentation of lotic systems caused by construction of dams has modified many aquatic communities. The objective of this study was to analyse changes in the aquatic insect community structure by discontinuity of habitat created by dams along the Ribeirão das Anhumas, a sub-basin of the Mogi-Guaçu River (state of São Paulo, Brazil). Entomofauna collection was carried out in 10 segments upstream and downstream of five dams along the longitudinal profile of the stream, with a quick sampling method using a D net (mesh 250 mm) with 2 minutes of sampling effort. The insects were sorted and identified to the lowest possible taxonomic level and analysed by the Shannon diversity index, ß diversity, richness estimated by rarefaction curves and relative participation of functional feeding groups. The results showed a slight reduction in diversity in the downstream segments, as well as along the longitudinal profile of the stream. However, there were no significant differences in abundance and richness between the upstream and downstream segments, indicating that the dams did not influence these variables. Differences were observed in the functional feeding groups along the longitudinal profile. Predator and gatherer insects were dominant in all segments analysed. The feeding group of shredders was more abundant in the segment DSIII with the participation of Marilia Müller (Odontoceridae - Trichoptera), although we observed a decrease of shredders and scrapers with the decrease of the canopy cover reducing values of ß diversity in the continuum of Ribeirão das Anhumas. This result demonstrated the importance of the conservation of the riparian vegetation in order to maintain the integrity of the stream.

Aquatic insect community structure under the influence of small dams in a stream of the Mogi-Guaçu river basin, state of São Paulo / Estrutura da comunidade de insetos aquáticos sob influência de pequenas represas em um ribeirão da bacia do Rio Mogi-Guaçu, Estado de São Paulo

The fragmentation of lotic systems caused by construction of dams has modified many aquatic communities. The objective of this study was to analyse changes in the aquatic insect community structure by discontinuity of habitat created by dams along the Ribeirão das Anhumas, a sub-basin of the Mogi-Guaçu River (state of São Paulo, Brazil). Entomofauna collection was carried out in 10 segments upstream and downstream of five dams along the longitudinal profile of the stream, with a quick sampling method using a D net (mesh 250 mm) with 2 minutes of sampling effort. The insects were sorted and identified to the lowest possible taxonomic level and analysed by the Shannon diversity index, β diversity, richness estimated by rarefaction curves and relative participation of functional feeding groups. The results showed a slight reduction in diversity in the downstream segments, as well as along the longitudinal profile of the stream. However, there were no significant differences in abundance and richness between the upstream and downstream segments, indicating that the dams did not influence these variables. Differences were observed in the functional feeding groups along the longitudinal profile. Predator and gatherer insects were dominant in all segments analysed. The feeding group of shredders was more abundant in the segment DSIII with the participation of Marilia Müller (Odontoceridae – Trichoptera), although we observed a decrease of shredders and scrapers with the decrease of the canopy cover reducing values of β diversity in the continuum of Ribeirão das Anhumas. This result demonstrated the importance of the conservation of the riparian vegetation in order to maintain the integrity of the stream.

A fragmentação de sistemas lóticos causadas pela construção de represas tem causado modificação na estrutura das comunidades aquáticas. O objetivo deste estudo foi analisar as mudanças na estrutura da comunidade de insetos aquáticos decorrentes da descontinuidade de habitat criada por represamentos ao longo do Ribeirão das Anhumas, uma sub-bacia do rio Mogi-Guaçu (Estado de São Paulo, Brasil). A coleta da entomofauna foi realizada em 10 segmentos à montante e à jusante de cinco represas ao longo do perfil longitudinal do ribeirão, pelo método de varredura com rede D (malha 250 mm) e esforço amostral de 2 minutos. Os insetos foram triados e identificados até o menor nível taxonômico possível e os diferentes grupos foram analisados pelo índice de diversidade de Shannon, diversidade β, riqueza estimada pela curva de rarefação e participação relativa dos grupos funcionais de alimentação. Os resultados apontaram ligeira redução na diversidade nos trechos à jusante, bem como ao longo do perfil longitudinal do ribeirão. Todavia, não houve diferenças significativas na abundância e riqueza entre os segmentos à montante e à jusante das represas, indicando que os represamentos não influenciaram nessas variáveis. Os resultados apontaram diferenças nos grupos funcionais de alimentação ao longo do perfil longitudinal. Os insetos predadores e coletores foram os grupos de alimentação predominantes em todos os segmentos analisados. O grupo dos insetos fragmentadores foi mais abudante no segmento DSIII com a participação de Marilia Müller (Odontoceridae- Trichoptera), embora observado um decréscimo de fragmentadores e rapaspadores com a redução da cobertura vegetal, reduzindo os valores dediversidade b no perfil longitudinal do Ribeirão das Anhumas. Os resultados demonstraram a importancia da conservação da vegetação ripária para a manutenção da integridade do ribeirão.

Riethia manauara n. sp., an Amazonian Chironomid (Diptera: Chironomidae) from Brazil.

One new species of Riethia Kieffer, Riethia manauara n. sp., is described and figured as male, pupa and larva. The generic diagnosis for pupae and larvae are emended. The specimens were collected from water systems in the Amazon Rainforest in northern Brazil.

Riethia manauara n. sp., an Amazonian Chironomid (Diptera: Chironomidae) from Brazil

One new species of Riethia Kieffer, Riethia manauara n. sp., is described and figured as male, pupa and larva. The generic diagnosis for pupae and larvae are emended. The specimens were collected from water systems in the Amazon Rainforest in northern Brazil.

Benthic macroinvertebrates of a tropical lake: Lake Caçó, MA, Brazil.

Benthic communities are highly relevant in the study of aquatic ecosystems, both for their role in the functioning of the ecosystem and also as markers or indicators of paleo-conditions. Their distribution, as in other communities, is conditioned by abiotic and biotic factors and to their interactions, which determine the structure of the community that is established. The aim of this study was to determine the taxonomic composition, abundance and spatial distribution of the benthic community, by collecting at 20 sampling sites in Caçó Lake (State of Maranhão, Brazil). Seasonal variation in these community parameters was analysed and related to the seasonal displacement of the Intertropical Convergence Zone. The results indicated that changes occur in the taxa richness, diversity and density of the benthic species of this lake that are mainly related to seasonality. All those parameters were higher in the dry than in the rainy period. The family Chironomidae (Diptera, Insecta) was the most important component of the community, representing approximately 50% of the total benthic fauna of the lake. The identification of the Chironomidae currently occurring in Lake Caçó is relevant, even at the genus level, considering the fact that this group produces fossilizing remains and could perhaps be good paleolimnological and paleoclimatic tracers that could be used to make inferences on past lake and climate conditions.

Benthic macroinvertebrates of a tropical lake: lake Caçó, MA, Brazil / Macroinvertebrados bentônicos de um lago tropical: lago Caço, MA, Brasil

Benthic communities are highly relevant in the study of aquatic ecosystems, both for their role in the functioning of the ecosystem and also as markers or indicators of paleo-conditions. Their distribution, as in other communities, is conditioned by abiotic and biotic factors and to their interactions, which determine the structure of the community that is established. The aim of this study was to determine the taxonomic composition, abundance and spatial distribution of the benthic community, by collecting at 20 sampling sites in Caçó Lake (State of Maranhão, Brazil). Seasonal variation in these community parameters was analysed and related to the seasonal displacement of the Intertropical Convergence Zone. The results indicated that changes occur in the taxa richness, diversity and density of the benthic species of this lake that are mainly related to seasonality. All those parameters were higher in the dry than in the rainy period. The family Chironomidae (Diptera, Insecta) was the most important component of the community, representing approximately 50 percent of the total benthic fauna of the lake. The identification of the Chironomidae currently occurring in Lake Caçó is relevant, even at the genus level, considering the fact that this group produces fossilizing remains and could perhaps be good paleolimnological and paleoclimatic tracers that could be used to make inferences on past lake and climate conditions.

As comunidades bentônicas são relevantes nos ecossistemas aquáticos devido ao seu papel no seu funcionamento e também como marcadores ou indicadores de paleocondições. Sua distribuição, similarmente à de outras comunidades, é condicionada por fatores abióticos e bióticos e pela interação entre eles, determinando a estrutura da comunidade que se estabelecerá. O objetivo do presente trabalho foi determinar a composição taxonômica, a abundância e a distribuição espacial da comunidade bentônica, amostrando-se em 20 pontos na lagoa do Caçó (Estado do Maranhão, Brasil). As variações sazonais nas características desta comunidade foram analisadas e relacionadas ao deslocamento sazonal da Zona de Convergência Intertropical. Os resultados indicaram que ocorrem mudanças na riqueza de taxons, diversidade e densidade da comunidade bentônica deste lago que são principalmente relacionadas à sazonalidade. Todas as variáveis analisadas foram maiores no período seco do que no chuvoso. Os organismos pertencentes à família Chironomidae (Diptera, Insecta) foram os mais importantes componentes da comunidade, representando aproximadamente 50 por cento do total da fauna. A identificação dos Chironomidae atualmente presentes no Lago Caçó, mesmo em nível de gênero, é relevante, considerando-se o fato de que as larvas deste grupo produzem remanescentes fósseis que podem ser bons traçadores paleolimnológicos e paleoclimáticos, podendo ser utilizados para fazer inferências sobre as condições passadas neste lago e no clima regional.

Phytophilous Chironomidae (Diptera) and other macroinvertebrates in the ox-bow Infernão Lake (Jataí Ecological Station, Luiz Antônio, SP, Brazil)

Infernão Lake, located within the Jataí Ecological Station in Luiz Antônio Municipal district (São Paulo State, Brazil), is one of the most typical ox-bow lake of the Mogi-Guaçu River, and it presents, as the main feature, its great quantity of aquatic macrophytes, whose intensive development, in the last years practically covered the whole mirror of water. With the purpose to point out the composition and to establish the relative participation of the phytophilic zoocoenosis that inhabits the different macrophytes of that lake, a collection program of the main vegetation stands was established. The collections, were carried out randomly, during dry season (1994), in stands of Salvinia auriculata, Utricularia sp., Cabomba piauhyensis, Eichhornia azurea and Scirpus cubensis being used specific methodology for each vegetable type. The analysis of the different macrophytes showed the presence of 4,130 macroinvertebrates of 28 families, in which Chironomidae (Diptera) and Naididae (Oligochaeta) were the most representative, contributing on the average with 51 percent and 25 percent of the total fauna. Asheum, Beardius, Chironomus, Goeldichironomus, Parachironomus and Polypedilum were the most abundant Chironomidae genera. Species of the genus Dero (Dero) and D. (Aulophorus) represented the most typical Naididae of the phytofauna. With clear faunistic gradient from the shore to the center of the lake, the taxocoenosis indicated low similarity (PSc < 50 percent), evidencing its own characteristics of each biotope. On the contrary, there was a high similarity (PSc > 60 percent) among the associated communities on different vegetables, when grouped into feeding guilds, with expressive participation, in most of the macrophytes, of the collector-gatherers category, except on S. auriculata, whose predators (> 50 percent) and collector-filterers (> 20 percent) dominance turned that zoocoenosis distinct from the others

Phytophilous chironomidae (Diptera) and other macroinvertebrates in the ox-bow Infernão Lake (Jatai Ecological Station, Luiz Antonio, SP, Brazil).

Infernão Lake, located within the Jataí Ecological Station in Luiz Ant nio Municipal district (São Paulo State, Brazil), is one of the most typical ox-bow lake of the Mogi-Guaçu River, and it presents, as the main feature, its great quantity of aquatic macrophytes, whose intensive development, in the last years practically covered the whole mirror of water. With the purpose to point out the composition and to establish the relative participation of the phytophilic zoocoenosis that inhabits the different macrophytes of that lake, a collection program of the main vegetation stands was established. The collections, were carried out randomly, during dry season (1994), in stands of Salvinia auriculata, Utricularia sp., Cabomba piauhyensis, Eichhornia azurea and Scirpus cubensis being used specific methodology for each vegetable type. The analysis of the different macrophytes showed the presence of 4,130 macroinvertebrates of 28 families, in which Chironomidae (Diptera) and Naididae (Oligochaeta) were the most representative, contributing on the average with 51% and 25% of the total fauna. Asheum, Beardius, Chironomus, Goeldichironomus, Parachironomus and Polypedilum were the most abundant Chironomidae genera. Species of the genus Dero (Dero) and D. (Aulophorus) represented the most typical Naididac of the phytofauna. With clear faunistic gradient from the shore to the center of the lake, the taxocoenosis indicated low similarity (PSc < 50%), evidencing its own characteristics of each biotope. On the contrary, there was a high similarity (PSc > 60%) among the associated communities on different vegetables, when grouped into feeding guilds, with expressive participation, in most of the macrophytes, of the collector-gatherers category, except on S. auriculata, whose predators (> 50%) and collector-filterers (> 20%) dominance turned that zoocoenosis distinct from the others.