Benthic macroinvertebrate community structure in a stream of the north-west region of Paran\ue1 State, Brazil

This study aimed to survey the benthic macroinvertebrate fauna of a first order stream located in an agricultural area, and to assess the environmental factors involved in the spatial distribution of this community. Invertebrates were gathered in November 2007 at three sampling sites distributed along the Itiz Stream, located in Marialva municipality, Paraná State. At each site, we measured the physical and chemical variables of the water, and then took four samples, using Surber sampler. In order to evaluate the differences in density, richness, diversity and evenness, we employed an ANOVA and a DCA to summarize biotic data. The invertebrates were categorized into functional groups and the BMWP score was applied to calculate the biological integrity of the environment. The faunal composition was represented by 103 taxa distributed across five phyla, of which the highest occurrence was of arthropods, especially insects. Higher density values were observed for Chironomidae, Ephemeroptera, Coleoptera and Trichoptera. The richness, diversity and density, as well as the density of gathering-collectors, were higher in the intermediate course of the stream. The distribution pattern of the taxa was mainly influenced by lentic or lotic characteristics of the sampled sites and microhabitats, as evidenced by the DCA. The BMWP indices indicated that the three sampling sites presented scores of excellent and good water quality. In the Itiz Stream, the presence of preserved marginal vegetation and the distance from urban centers that generate pollution, combined with peculiarities of each sampling site, influenced the structure of the benthic community

Caracterização morfológica e molecular de Corbicula (Mollusca, Bivalvia) no reservatório de Rosana, Brasil - DOI: 10.4025/actascibiolsci.v27i4.1274

The purpose of the present study was to verify, using RAPD and ISSR molecular techniques associated with the morphological characterization of bivalve shells, if the morphologically distinct specimens of Corbicula fluminea sampled at Rosana Reservoir belong to different species. The foot muscle tissue of the three groups (G1, G2, and G3) of Corbicula was removed and frozen in liquid nitrogen to the DNA analyze. Morphometric variables of the shell indicated significant differences among the specimens of Corbicula. On the other hand, molecular analyses revealed genetic similarity among the specimens, showing the nonexistence of molecular polymorphism. The data confirmed that the two morphologically different groups also belong to the species C. fluminea, showing the occurrence of phenotypic plasticity, probably caused by environmental or biotic factorsO objetivo do presente estudo foi verificar através de técnicas moleculares, RAPD e ISSR aliadas à caracterização morfológica da concha dos bivalves, se os indivíduos morfologicamente distintos de Corbicula fluminea amostrados no reservatório de Rosana pertencem a espécies diferentes. O tecido muscular do pé dos três grupos (G1, G2 e G3) de Corbicula foi removido e congelado em nitrogênio líquido para a análise do DNA. As variáveis morfométricas das conchas indicaram diferenças significativas entre os indivíduos de Corbicula. Por outro lado, as análises moleculares revelaram similaridade genética, evidenciando a não existência de polimorfismo molecular. Os resultados confirmam que os dois grupos diferentes morfologicamente também pertencem a espécie C. fluminea, demonstrando a ocorrência de plasticidade fenotípica, provavelmente causada por fatores bióticos ou ambientai

Caloric variability of Corbicula fluminea (Mollusca, Bivalvia) in Rosana Reservoir, Brazil

The purpose of the present study was to investigate temporal and longitudinal variation of caloric density of Corbicula fluminea in Rosana Reservoir. Significant differences concerning the caloric density of C. fluminea were observed throughout the year at the three reservoir sites. The caloric density variation during the year was probably related to reproductive activity, which demanded higher allocation of energy in certain period. The food source used by this species might be an important factor in the caloric value temporal and spatial variation of C. fluminea in Rosana Reservoir.<br>O objetivo deste estudo foi investigar a variação temporal e longitudinal da densidade calórica de C. fluminea no reservatório de Rosana. Diferenças significativas na densidade calórica de C. fluminea foram observadas ao longo do ano e nas três estações do reservatório. A variação na densidade calórica de C. fluminea, durante o ano, provavelmente foi relacionada à atividade reprodutiva, que exige uma maior alocação de energia em determinado período. O recurso alimentar utilizado por esta espécie pode ser um importante fator na variação temporal e espacial do valor calórico de C. fluminea no reservatório de Rosana