Ana Emilia Siegloch

Composição de Heteroptera aquáticos e semi-aquáticos na área de abrangência da U.H.E. Dona Francisca, RS, Brasil: fase de pré-enchimento

Neste estudo, foi analisada a composicao dos Heteroptera do curso medio da bacia do rio Jacui, RS, Brasil, previamente a construcao da U.H.E. Dona Francisca, bem como alguns fatores abioticos que poderiam afetar a distribuicao e a abundância destes organismos. Nos ambientes lenticos, amostragens quantitativas foram realizadas utilizando-se peneiras, em seis localidades (janeiro 2000). Nos ambientes loticos, as coletas foram feitas atraves de amostrador de Surber (de maio a outubro de 2000), privilegiando-se a captura de especies tipicamente bentonicas. Em cada estacao, pH, oxigenio dissolvido, precipitacao mensal, temperatura do ar e da agua e profundidade foram medidos. Nos rios e riachos, a velocidade da corrente tambem foi registrada. Quinze especies foram registradas nos ambientes lenticos, sendo Belostoma sp. e Notonecta sp. as dominantes (70%). A abundância, a riqueza e os indices de diversidade foram mais altos nos locais com maiores dimensoes. Nos ambientes loticos, foram assinaladas duas especies de Naucoridae, Ambrysus teutonius La Rivers, 1951 e Cryphocricus vianai De Carlo, 1951, sendo a primeira dominante (65%). A abundância foi maior nos pontos com maior sombreamento, presenca de arvores e/ou com detritos vegetais, ou com a macrofita Podostemum sp. (Podostemaceae) no fundo, e mais baixa em locais com curso semi-regulado. Possivelmente, fatores como temperatura e precipitacao acumulada estejam relacionados com a abundância mensal dos Naucoridae. Os resultados deste estudo servirao de subsidio para futuros estudos de impacto ambiental apos o enchimento do reservatorio da U.H.E. Dona Francisca.

Effect of land use on mayfly assemblages structure in Neotropical headwater streams

The aim of this study was to test the effect of agricultural and forestry land use on the structure of mayfly assemblages in low-order streams. Twenty-nine headwater streams were investigated in the state of São Paulo. We analyzed 15 streams in pristine areas (mixed tropical rainforest, semideciduous forest and dense tropical rainforest), and 14 streams covered with sugarcane, eucalyptus and pasture. Mayfly richness obtained by rarefaction curves was higher in pristine areas (21 genera), especially in mixed and semideciduous forest when compared to land use (9 genera), where values were particularly low in sugarcane plantation (3 genera). The non-metric multidimensional scaling (NMDS) ordination showed clear difference in mayfly assemblages between land uses and pristine areas, supported by analysis of similarity (R=0.67, p=0.001). In partial redundancy analysis (pRDA), the environmental descriptors that best explained differences in assemblage structure were Riparian, Channel and Environmental Inventory (RCE) index score, percentage of fine sediment stream substrate, water pH and land elevation. Our results show that agricultural and forestry land use has a strong negative effect on the structure of mayfly assemblages. These results also support the use of mayflies as environmental indicators, as some genera were sensitive to changes in land use, while others responded to naturally occurring changes in the study area.

Diversity of Ephemeroptera (Insecta) of the Serra da Mantiqueira and Serra do Mar, southeastern Brazil

The aim of this study was to inventory the mayfly fauna, based on nymphal and alate stages, in Serra da Mantiqueira and in Serra do Mar, Sao Paulo State, as well as to present information about habitats used by the genera. Nymphs were collected in several streams and mesohabitats with a Surber sampler and the winged stages with light attraction methods, entomological nets, and Malaise traps. In all, eight families and 33 genera were recorded, representing a very significant portion of the Brazilian fauna (80% of families and 49% of genera). Furthermore, it was possible to identify 11 species, of which two are new records for the state: Tricorythodes santarita Traver and Caenis reissi Malzacher. Despite the high diversity recorded, the accumulation curves presented an ascending form, indicating an increase in the number of genera with additional sampling effort. The high richness found in these areas are in agreement with the high biodiversity of the Atlantic Forest biome and the sampling effort employed, which included the use of different methods, the collection of both nymphs and winged stages, and the sampling of a large area with diverse streams and habitats.

Diversity and Distribution of Ephemeroptera and Trichoptera in Southern Brazil Wetlands

Abstract Ephemeroptera and Trichoptera larvae are important components of freshwater benthic communities. However, the environmental factors that determine Ephemeroptera and Trichoptera diversity and distribution in wetland systems of the Neotropical region are not well known. The objectives of this study were to: 1) conduct a diversity survey of mayflies and caddisflies in 140 wetlands in an extensive area of the Neotropical region (∼220,000 km2, southern Brazil), and 2) determine how much variation in mayfly and caddisfly richness and composition is explained by wetland area, altitude, hydroperiod, aquatic vegetation and water conductivity. A total of 5207 individuals distributed among 16 genera of Trichoptera and Ephemeroptera were collected in the studied wetlands. The mayflies were represented by eight genera, and comprised 94.6% of the collected individuals. The richness of Ephemeroptera and Trichoptera was similar between permanent and intermittent wetlands, and it did not differ significantly between aquatic bed and emergent wetlands. However, the density was higher in permanent than in intermittent wetlands, and it was higher in aquatic bed than in emergent wetlands. While the richness and density were negatively associated with altitude and water conductivity, the composition was associated with wetland area and altitude. In terms of the conservation, there is a need to promote conservation of all wetland systems in southern Brazil, regardless of their area and altitude. These arguments are essential to develop conservation and management programs of wetlands in this region.

Segesta riograndensis , Ephemeroptera, Leptophlebiidae, Atalophlebiinae: first record from state of Mato Grosso do Sul, western Brazil

The mayfly Segesta riograndensis (Ephemeroptera: Leptophlebiidae) was recently described by Siegloch et al. (2006) based on larvae from southern Brazil, municipality of Independencia, northwest from state of Rio Grande do Sul. The larvae can be distinguished from other genera of Atalophlebiinae by the following combination of characters: clypeus slightly divergent with sinuous margin; labrum with shallow emargination and three nonprominent denticles; maxillary palpi very large and curved with setae in varied combinations; labial palpi very long and curved, with long setae (Figure 1A-B); paraglossae wider than long; abdominal posterolateral spines gradually longer posteriorly. Here we are extending the range distribution of S. riograndensis in 850 kilometers to the northwest Rio Grande do Sul to state of Mato Grosso do Sul (Figure 2).