Inventário das aranhas arborícolas de três regiões de Santa Maria, RS, Brasil

This study describes the results 01 seasonal collects 01 arboreal spiders during the years 01 1995 and 1996 in Perau Velho, Cidade dos Meninos and São Marcos, in the outskirts 01 Santa Maria city in Rio Grande do Sul state. They were captured 2381 specimens distributed in 20 families and 65 genera. It is also presented a preliminary list 01 species.Relata-se o resultado de coletas sazonias de aranhas arborícolas realizadas nos anos de 19959 e 1996, nas localidades de Perau Velho, Cidade dos Meninos e São Marcos, nos arredores de Santa Maria, RS. Foram capturados 2381 espécimes, distribuídos em 20 famílias e 65 gêneros. Apresenta-se também uma lista preliminar de espécies

Composição de Heteroptera aquáticos e semi-aquáticos na área de abrangência da U.H.E. Dona Francisca, RS, Brasil: fase de pré-enchimento Composition of aquatic and semi-aquatic Heteroptera at the Hydroelectric Power Station of Dona Francisca region, RS, Brazil: before dam construction

Neste estudo, foi analisada a composição dos Heteroptera do curso médio da bacia do rio Jacuí, RS, Brasil, previamente à construção da U.H.E. Dona Francisca, bem como alguns fatores abióticos que poderiam afetar a distribuição e a abundância destes organismos. Nos ambientes lênticos, amostragens quantitativas foram realizadas utilizando-se peneiras, em seis localidades (janeiro 2000). Nos ambientes lóticos, as coletas foram feitas através de amostrador de Surber (de maio a outubro de 2000), privilegiando-se a captura de espécies tipicamente bentônicas. Em cada estação, pH, oxigênio dissolvido, precipitação mensal, temperatura do ar e da água e profundidade foram medidos. Nos rios e riachos, a velocidade da corrente também foi registrada. Quinze espécies foram registradas nos ambientes lênticos, sendo Belostoma sp. e Notonecta sp. as dominantes (70%). A abundância, a riqueza e os índices de diversidade foram mais altos nos locais com maiores dimensões. Nos ambientes lóticos, foram assinaladas duas espécies 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, presença de árvores e/ou com detritos vegetais, ou com a macrófita Podostemum sp. (Podostemaceae) no fundo, e mais baixa em locais com curso semi-regulado. Possivelmente, fatores como temperatura e precipitação acumulada estejam relacionados com a abundância mensal dos Naucoridae. Os resultados deste estudo servirão de subsídio para futuros estudos de impacto ambiental após o enchimento do reservatório da U.H.E. Dona Francisca.The Heteroptera composition in the middle course of the Jacuí River basin, RS, Brazil, and some abiotic factors that might affect their distribution and abundance were studied previously to the Dona Francisca dam construction. The insects were quantitatively sampled in six sites, in lentic environments, with sieves (January 2000). In lotic environments, the samplings of the benthic Heteroptera were carried out in thirteen sites with a Surber sampler (from May to October 2000). In each station, pH, dissolved oxygen, monthly precipitation, water and air temperatures, and depth were measured. In rivers and streams, the current velocity was also registered. Fifteen species were registered in the lentic environments, being Belostoma sp. and Notonecta sp. the dominant species (70%). Abundance, richness and diversity indexes were higher in sites with larger dimensions. In running waters, two species of Naucoridae were recorded, Ambrysus teutonius La Rivers, 1951 and Cryphocricus vianai De Carlo, 1951, being the former dominant (65%). The abundance was greater in sampling points with dense canopy and/or with litter, or with the macrophyte Podostemum sp. (Podostemaceae), and was smaller in semi-regulated sites. Possibly, the monthly abundance of the Naucoridae be influenced by abiotic factors, such as temperature and precipitation. The results of this study will subsidize future impact researches after Dona Francisca dam has been built

Composition and diversity of Trichoptera (Insecta) larvae communities in the middle section of the Jacuí river and some tributaries, State of Rio Grande do Sul, Brazil Composição e diversidade de comunidades de larvas de Trichoptera (Insecta) no trecho médio do rio Jacuí e alguns tributários, Estado do Rio Grande do Sul, Brasil

The taxonomic composition and diversity of Trichoptera larvae communities were studied in four lotic sites in central region of State of Rio Grande do Sul. Sampling was done monthly from June, 2001 to May, 2002 in four sites located at the middle section of Jacuí River (Point 4) and in three tributaries (Carijinho River - Point 1; Lajeado da Gringa - Point 2 and Lajeado do Gringo - Point 3), with a Surber sampler. The total number of larvae collected was 29,143, belonging to 25 genera distributed in nine families; twenty of these genera are new records for the State. The highest abundance was found at Point 2 (n = 12,547). The highest standardized richness, for a 1,177 specimens sample chosen by chance, was recorded at Point 1, followed by Point 4 (17.7 and 16 genera, respectively). The highest diversity was found at Point 1, and the lowest at Point 3 (H' = 1.31 and H' = 0.77, respectively). Point 1 had the lowest anthropic influence and the best preserved riparian vegetation, while Point 3 presented the highest anthropic impact, and a very reduced riparian vegetation. The diversity of Trichoptera observed in this study is low, compared to the estimated maximum theoretical diversity. Low diversity values are related to the low evenness, since the richness was relatively high. The Trichoptera larvae communities seem to be related to the food availability and physical features (riparian vegetation and anthropic influence) of the study sites.A composição taxonômica e a diversidade de comunidades de larvas de Trichoptera foram estudadas em quatro ambientes lóticos na região central do Estado do Rio Grande do Sul. As amostras foram coletadas mensalmente de junho de 2001 a maio de 2002 em quarto pontos, localizados no trecho médio do Rio Jacuí (Ponto 4) e em três tributários (Rio Carijinho - Ponto 1; Lajeado da Gringa - Ponto 2 e Lajeado do Gringo - Ponto 3), com amostrador de Surber. O número total de larvas coletado foi 29.143, pertencentes a 25 gêneros distribuídos em nove famílias; vinte destes gêneros constituem registros novos para o Estado. A maior abundância foi encontrada no Ponto 2 (n = 12.547). A maior riqueza padronizada, para uma amostra de 1.177 espécimes retirados ao acaso, foi registrada no Ponto 1, seguida pelo Ponto 4 (17,7 e 16 gêneros, respectivamente). A maior diversidade foi encontrada no Ponto 1 e a menor no Ponto 3 (H' = 1,31 e H' = 0,77, respectivamente). O Ponto 1 possui a menor influência antrópica e a vegetação ripária melhor conservada, enquanto o Ponto 3 apresentou o maior impacto antrópico e a vegetação ripária muito reduzida. A diversidade de Trichoptera observada neste estudo foi baixa, comparada com a diversidade teórica máxima estimada. Os baixos valores de diversidade registrados estão relacionados à baixa equidade, pois a riqueza foi relativamente alta. As comunidades de larvas de Trichoptera parecem estar relacionadas com a disponibilidade alimentar e as características físicas (vegetação ripária e influência antrópica) dos ambientes estudados

Diet of Iheringichthys labrosus (Siluriformes, Pimelodidae) in the Ibicuí River, Southern Brazil

The diet of the benthic-feeding fish Iheringichthys labrosus (Lütken, 1874) was analyzed. Samples were taken bimonthly from December 1999 to January 2002, in three sites of the Ibicuí River, a tributary of Uruguay River basin (Rio Grande do Sul, Brazil). In each sampling point the specimens were collected in lentic and lotic environments. Gillnets and trammel nets were examined every 6 hours (6h, 12h, 18h and 24h). Diet description was based on the frequency of occurrence and the volume of each food item to obtain the Alimentary Index (IAi). The average stomach fullness was adopted to detect variations in the feeding activity according to the season, the circadian rhythm and the environment. Chironomids were the most important food item, followed by mollusks, and feeding activity was highest in summer, during daylight (6h and 12h), and in the lotic environment of the second sampling point

Composition and diversity of Ephemeroptera (Insecta) nymph communities in the middle section of the Jacu\ued River and some tributaries, southern Brazil

The taxonomic composition and diversity of assemblages of Ephemeroptera nymphs of four lotic environments in the central region of State of Rio Grande do Sul, a subtropical area in southern Brazil, were evaluated. Samplings were done monthly, with a Surber sampler, from June 2001 to May 2002, in the Jacuí River and three of its tributaries. The total number of nymphs collected in the four sampling sites was 11,007 in five families and 19 genera, of these, 11 are new records for the State. The highest diversity occurred in Point 4 (H'=2.41) and the lowest in Point 2 (H'=1.69). Point 4 had the highest environmental stability, conservation of the riparian vegetation and the lowest anthropic impact, while Point 2 presented a large environmental simplification due to a direct anthropic influence (e.g. domestic sewerage, trampling by cattle). The diversity of nymphs observed in the total area is high, compared to the estimated maximum theoretical diversity; a result of the high evenness and richness recorded. Rarefaction curves, calculated for a sample of 1,018 specimens, showed a similar expectation of richness for the four sampling sites. This result seems to be associated with the overall environmental homogeneity of the region caused by long-term alterations (land use and deforestation). In summary, higher diversity of Ephemeroptera nymph assemblages seems to be associated with habitat complexity, a good vegetation cover and a lower anthropic influence

Fidelity of molluscan assemblages from the touro passo formation (pleistocene-holocene), southern brazil: taphonomy as a tool for discovering natural baselines for freshwater communities

This study is the first assessment of mollusk fossil assemblages relative to the compositional fidelity of modern mollusk living and death assemblages. It also shows that the sedimentary record can provide information on the original, non-human-impacted, freshwater malacofauna biodiversity, based on Late Pleistocene shells. The fossil mollusk assemblage from the Touro Passo Formation (Pleistocene-Holocene) was compared to living and death assemblages of the Touro Passo River, southern Brazil, revealing little resemblance between fossil and live-dead species composition. Although the living and death assemblages agree closely in richness, species composition, and species relative abundances (both proportional and rank), the fossil assemblage differs significantly from both modern assemblages in most of these measures. The fossil assemblage is dominated by the native endemic corbiculid bivalve Cyanocyclas limosa and the gastropod Heleobia aff. bertoniana. These are absent in the living assemblages, and both living and death assemblages are dominated by the alien Asiatic corbiculid C. fluminea, which is absent in the fossil assemblage. The fossil assemblage also contains, overall, a higher proportional abundance of relatively thick-shelled species, suggesting a genuine bias against the thinner- and smaller-shelled species. Our results suggest that contemporary environmental changes, such as the introduction of some alien freshwater mollusk species, together with post-burial taphonomic processes, are the main factors leading to the poor fidelity of the fossil assemblage studied. Hence, the taxonomic composition of the Late Pleistocene mollusks from the Touro Passo Formation probably would show greater similarity to present-day assemblages wherever the mollusk biodiversity is not disturbed by human activities