Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are often used to assess the conditions of aquatic environments, but few studies have examined the differences in these communities between riffles and pools. Our objective was to test whether riffles shelter greater richness and abundance of EPT, as well as to assess the sensitivity of these insects for detecting impacts from different land uses in streams in southeastern Brazil. Samples were collected in the dry season of 2012 with a Surber sampler in riffles and pools of nine streams (forest, pasture, and urban areas). Principal component analysis distinguished the streams according to different land uses as a function of percentage of plant cover and water oxygenation level and showed partial distinction between riffles and pools as a function of current speed and percentage of ultrafine sand. Detrended correspondence analysis indicated the distinction in EPT composition between riffles and pools, except in urban streams. The results of this study confirm the expected differences in the EPT fauna structure between riffles and pools, especially in forest and pasture environments. The individual metrics of riffle and pool assemblages showed significantly different responses to land use. Therefore, we suggest individual sampling of riffles and pools, since the metrics of these assemblages’ insects can differ between these habitats and influence the results of assessments in low-order streams.

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Aim The objectives of this study were to evaluate which allometric measurements of Leptonema larvae are most suitable in order to develop mathematical equations to describe biomass relationships for the population of this taxon in a reference condition headwater stream. Methods We measured four body dimensions (body length, interocular distance, horizontal width of cephalic capsule and vertical width of the cephalic capsule) of 65 Leptonema larvae, which were collected in February 2022, in the Taboões spring, Serra do Rola Moça State Park, Minas Gerais, using a Surber sampler. For the determination of allometric measurements, each individual was photographed under a dissecting stereomicroscope (Leica M80) equipped with a digital camera. Each photographed specimen's length was measured using the Motic Image Plus 2.0 software. After measuring the linear body dimension and direct measurement of the biomass, we used these values to calculate the length-mass mathematical equations. To the equations use power models: DM = a Lb, where a/b are constants, DM is the dry mass, L is the linear body dimension. Results Among body dimensions of Leptonema larvae, body length showed the greatest range of variation, with values ranging from 4.03 to 25.28 mm, followed by head capsule vertical width (0.51 - 2.69 mm), head capsule horizontal width (0.55 - 2.22 mm) and interocular distance (0.24 - 1.88 mm). Our results show that body length provided the best-fitting equation for estimating biomass (R2 = 0.90). However, we observed a close fit between the other allometric measures, including high coefficients of determination, head capsule horizontal width (R2 = 0.85), interocular distance (R2 = 0.82), head capsule vertical width (R2 = 0.78). Conclusions These results will be useful in providing the best allometric measurement and equations to estimate the biomass of Leptonema larvae from the tropics.

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Nascentes são afloramentos do lençol freático que formam fluxos de água importantes na prestação de serviços ecossistêmicos, como irrigação de florestas, fornecimento de água para o consumo humano e habitat para a biota aquática. No Brasil, áreas de Mata Atlântica estão sendo gradativamente substituídas por culturas de eucalipto, alterando, comumente, a composição do substrato das nascentes. O objetivo deste estudo foi verificar se a composição granulométrica do sedimento de nascentes em áreas de floresta difere de nascentes em áreas plantadas com eucalipto. A hipótese testada foi que nascentes em áreas de eucalipto apresentam diferenças na composição granulométrica e menor porcentagem de matéria orgânica quando comparadas com nascentes em áreas de floresta. Para tanto, foi coletado o sedimento de 20 nascentes, todas pertencentes à bacia do rio Paraíba do Sul, situadas no estado de Minas Gerais, Brasil. Foi possível observar que as nascentes em áreas de floresta estiveram associadas com areia muito grossa, enquanto que aquelas em área de eucalipto estiveram associadas a partículas de granulometria mais fina. Em relação à matéria orgânica, não foi observada diferença significativa entre as duas áreas. O estudo enfatiza a importância da vegetação ciliar para mitigar potenciais impactos da silvicultura do eucalipto no sedimento das nascentes.

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