Diet of Astyanax paranae (Characidae) in streams with different riparian land covers in the Passa-Cinco River basin, southeastern Brazil

An analysis of the diet of Astyanax paranae Eigenmann, 1914 in nine streams located in the Passa-Cinco River basin (upper Paraná River system) was performed to investigate the feeding habits of this species, check for possible spatial variations in diet and to investigate the influence of riparian vegetation in the composition of the diet. Stomach contents of 243 specimens were analyzed by the methods of relative frequency of occurrence and volume, and the diet was characterized by the alimentary index (AIi). The species showed insectivorous feeding habits, with a predominance of terrestrial and aquatic insects in the diet, varying by location. In most streams, resources of allochthonous origin were the most consumed. The participation of aquatic insects and terrestrial plants were high in most streams, while terrestrial insects and invertebrates were highest in streams with a greater presence of riparian forest. The two streams located draining pasture fields were the only places were A. paranae consumed algae and macrophyte fragments. These results were corroborated by the analysis of similarity (ANOSIM): the descriptor "percentage of riparian forest" was the highest environmental influence on the diet of A. paranae. The study shows that riparian forest percentage on the stream reach determines the species diet composition, but A. paranae is also able to gather enough food resources in a variety of severely degraded environments.

Oligochaetes (Annelida, Clitellata) in a neotropical stream: a mesohabitat approach

This paper analyses the relationship among mesohabitat and aquatic oligochaete species in the Galharada Stream (Campos do Jordão State Park, state of São Paulo, Brazil). Between August 2005 and May 2006 a total of 192 samples were obtained in areas of four different mesohabitats: riffle leaf litter (RL), pool leaf litter (PL), pool sediment (PS) and interstitial sediment from rocky beds in riffle areas (IS). In the mesohabitats sampled, 2007 specimens were identified, belonging to two families (Naididae and Enchytraeidae). Among the oligochaetes identified Naididae was represented by six genera (Allonais, Chaetogaster, Nais, Pristina, Aulodrilus and Limnodrilus). Principal components analysis (PCA) revealed the first two axes explained 85.1% of the total variance of the data. Limnodrilus hoffmeisteri Claparede, 1862 and Aulodrilus limnobius Bretscher, 1899 were associated with the pool areas (PL and PS). Most species of genera Pristina and Nais demonstrated apparent affinity with the riffle mesohabitats. The Indicator Species Analysis (IndVal) revealed that Nais communis Piguet, 1906, Pristina leidyi Smith, 1896 and Pristina (Pristinella) jenkinae (Stephenson, 1931) are indicative of RL mesohabitat, while family Enchytraeidae was considered indicative of PL mesohabitat.

Synchaeta jollyae (Shiel & Koste) (Rotifera, Synchaetidae): an overlooked species or a newcomer in Neotropical freshwaters?

Populations of Synchaeta jollyae (Shiel & Koste, 1993) (Rotifera), a species recently recorded for the first time in Brazil and South America, were analyzed in reservoirs in Southeast Brazil. Sampling was carried out monthly from August 2006 to July 2007 at Furnas Reservoir in the Rio Grande basin, state of Minas Gerais, and in four cascade reservoirs in the Tietê River basin (Barra Bonita, Bariri, Ibitinga and Nova Avanhandava) state of São Paulo, in June and September 2008 and in January and May 2009. Synchaeta jollyae occurred in most samples and periods. From the results obtained it is evident that S. jollyae occurs in water bodies of varied trophic status but reaches larger populations in eutrophic water bodies and during lower temperature periods. The greatest densities of S. jollyae were found in the eutrophic Bariri Reservoir, on the Tietê River, during the winter. Mann-Whitney test confirmed the significant difference between the population densities in periods of high and low temperatures, with populations reaching higher densities at lower temperatures. It is not yet possible to tell whether S. jollyae is a widely distributed species that has been overlooked in previous plankton studies in South America. Wherever these populations of S. jollyae might have originated, it appears to be a species well established and adapted to a wide range of conditions in the Neotropics.

Population ecology of the multivoltine Neotropical gall midge Eugeniamyia dispar (Diptera, Cecidomyiidae)

Our understanding of the population ecology of insect gallers is largely built on examples from temperate zones, but tropical and subtropical gallers may present distinct patterns of abundance and distribution across time. Eugeniamyia dispar Maia, Mendonça & Romanowski, 1996 is a multivoltine Neotropical cecidomyiid that induces spongy leaf galls on Eugenia uniflora (Myrtaceae). Galls were censused in the urban area of Porto Alegre, southern Brazil on six plants at two sites, for two years, at roughly weekly intervals. Overall 9,694 eggs, galling attempts and galls were counted. New galls continuously appear on developing leaves, but galls with live inducers are absent from June to at least early August. Galls on a same shoot develop synchronically, thus the shoot is probably the unit for oviposition. Given the also synchronic appearance of galls on different plants on a site, it seems midges can disperse and attack close-by plants. Gall cohorts varied in abundance by two orders of magnitude; there were more galls during summer than for spring and autumn, in a wave-like pattern. Host plant leaf production was seasonal, with low production during winter and cyclic production during the rest of the year. Perhaps because of this very variable pattern, gall abundance did not follow leaf production: this galler is not synchronised with its host at least during most of the year. This multivoltine gall inducer with "labile" galls, short development time, partially overlapping generations and low host synchronisation differs from the commonly studied species of the temperate regions providing a subject for ecological comparisons.

Macroinvertebrates under stochastic hydrological disturbance in Cerrado streams of Central Brazil

In the Cerrado vegetation, where the seasonal is well defined, rainfall has an important role in controlling the flow of streams and consequently on the structure of macroinvertebrates community. Despite the effects of rainfall associated with seasonality are well studied, little is known about the effects of stochastic rains on the community. In the present study we evaluated the structure and faunal composition of four first-order streams in Central Brazil during the dry season in two years, with and without stochastic rains. Community sampling was done by colonization of boards of high density polyethylene (HDPE), removed after one month submerged in streams. Analysis of Variance (ANOVA) performed indicated no difference in rarefied richness between the two periods, different from numeric density of organisms that was higher in the period without disturbance; moreover, the Detrended Correspondence Analysis (DCA) revealed differences in faunal composition between the two periods. Our results indicate that stochastic rainfall is an important factor in structuring the macroinvertebrates community in studied region.

Effects of environmental factors on community structure of Leptophlebiidae (Insecta, Ephemeroptera) in Cerrado streams, Brazil

We analyzed the effects of environmental factors on abundance, species richness, and functional group richness of Leptophlebiidae in 16 sampling points along four Cerrado streams. Across three periods of 2005, we collected 5,492 larvae from 14 species in stream bed substrate. These species belong to three functional feeding groups: scrapers, filtering collectors and shredders. The abundance and species richness were not affected by water quality, but habitat quality related to presence of riparian vegetation had positive effects on the abundance of shredders. Our results add important information on the natural history of the species and functional groups of aquatic insects and also provide relevant data for the monitoring and conservation of streams in the Brazilian Cerrado.

Effects of anthropogenic impacts on benthic macroinvertebrates assemblages in subtropical mountain streams

The nature of the riparian and surrounding landscape has been modified by anthropogenic activities, which may subsequently alter the composition and functional structure of macroinvertebrate assemblages. The effect of these changes on function of benthic fauna is difficult to assess due to the scarce knowledge on functional structures in tropical streams. In this study we evaluate whether sites impacted and unimpacted by anthropogenic alterations differed in assemblage composition and density, richness and diversity of each functional feeding group. The selection of the sites was related to their distinct riparian characteristics, following the QBRy riparian quality index. Collector-gatherer was the dominant functional feeding group, comprising 91% of total density, whereas the proportion of shredders was very low, representing less of 0.5% of total density. Asemblage composition of macroinvertebrates differed between impacted and unimpacted sites. Predators were dominant in taxa number, representing about 60% of total taxa richness. In addition, the diversity and richness of collector-gatherers differed significantly between degraded and unimpacted sites, reflecting the sensitivity of this group to environmental changes and the utility to be used in the assessment of anthropogenic modifications. The results of this study reinforce the idea that riparian corridor management is critical for the distribution of macroinvertebrate assemblages as well as functional organization of lotic streams.

Assessment of fish assemblages in streams of different orders in the Upper Paraná River basin, Central Brazil

The aim of this study was to test whether the richness observed and the biomass per trophic group of fish assemblages vary depending on the order (1st and 2nd) of the streams located in three different basins of the Upper Paraná River Basin, Central Brazil. Samples were collected between April and September, 2009, in 27 streams of the Meia Ponte, Piracanjuba and Santa Maria River basins. A total of 4,879 specimens were collected distributed in 59 species and 19 families. The statistical analyses carried out indicate that the observed richness and biomass of omnivore fish were influenced by the interaction of two factors: stream order and basin. The 2nd order streams located in the Santa Maria basin presented significant differences in the observed richness and omnivore biomass when compared to i) 1st order streams in the same basin (only richness) or in the Piracanjuba and Meia Ponte basin; ii) 2nd order streams in the Piracanjuba (only omnivore biomass) and Meia Ponte Rivers basins. Results are discussed considering the influence of geomorphic processes on fish assemblages and food availability.

Taxonomic and numeric structure of Chironomidae (Diptera) in different habitats of a Neotropical floodplain

We characterized the local benthic Chironomidae by analyzing the numerical density, biomass, diversity index of Shannon-Wiener and dominance of larvae in the main channel of the Ivinhema River, in a secondary channel, in five lakes connected to the main channel and in five lakes without connection. Of the 68 taxa identified, Aedokritus sp., Tanytarsus sp., Chironomus strenzkei Fittkau, 1968 and Procladius sp.1 were found in all sampling sites and were considered morphospecies with greater of greatest ecological plasticity. Chironomus strenzkei Fittkau, 1968, contributed with the greatest biomass in the central region of lakes without connection, whereas Aedokritus sp. dominated in the littoral of lakes. The greater values of diversity indices in the littoral region of channels were due to the greater water flow and to the higher food availability in these areas. The dominance indices, by contrast, were greater on the central region of these environments. The littoral region has exclusive characteristics, representing habitats that could play important controlling in the numerical density and index diversity on the ecosystem, whereas that the biomass of benthic invertebrates in the central region in some biotopes would have different spatial probably according organisms drift.

Taxonomic review of the Neotropical genus Neopachylus (Arachnida, Opiliones, Gonyleptidae)

A taxonomic review of the genus Neopachylus Roewer, 1913 together with keys to the species for both males and females are presented. Gephyropachylus marginatus Mello-Leitão, 1931 is considered a junior subjective synonym of Neopachylus serrinha Soares & Soares, 1947, and Huralvius incertus Mello-Leitão, 1935 is considered a synonym of Neopachylus nebulosus (Mello-Leitão, 1936). This genus is restricted to southern Brazil, occurring in states of Paraná, Santa Catarina and Rio Grande do Sul.

Assemblage of immature Odonata (Insecta, Anisoptera) in streams of the Mato Grosso do Sul State: spatial implications

ABSTRACT This study investigated the assemblages attributes (composition, abundance, richness, diversity and evenness) and the most representative genera of Odonata, Anisoptera at Água Boa and Perobão Streams, Iguatemi River basin, Brazil. Both are first order streams with similar length that are impacted by riparian forest removal and silting. Quarterly samplings were conducted from March to December 2008 in the upper, intermediate and lower stretch of each stream. The Mantel test was used to check the influence of spatial autocorrelation on the Odonata composition. Spatial variations in the composition were summarized by the Principal Coordinates Analysis (PCoA) using Mantel test residuals. The effects of spatial correlation on richness and abundance were investigated by the spatial correlogram of Moranʼs I coefficients. The most representative genera in each stream were identified by the Indicator Value Method. The spatial variations in the attributes of the assemblages were assessed using analysis of variance of null models. We collected 500 immature individuals of 23 genera and three families. Among the attributes analyzed only the composition and abundance showed significant spatial differences, with the highest mean abundance found in the Perobão Stream. Miathyria and Zenithoptera were the indicator genera of the Água Boa Stream and Erythrodiplax, Libellula, Macrothemis, Progomphus and Tramea were the indicator genera of the Perobão Stream.

External morphology of the immature stages of Neotropical heliconians: X. Heliconius sara apseudes (Lepidoptera, Nymphalidae, Heliconiinae)

ABSTRACT The biology and morphology of the immature stages of Heliconius sara apseudes (Hübner, [1813]) are still little known. External features of the egg, larvae and pupa of H. sara apseudes are described and illustrated, based upon light and scanning electron microscopy. Eggs with smooth carina, first instar larva with scaly setae, and body of second to fifth instars covered with scattered pinnacles distinguish H. sara apseudes from other heliconiine species.

Lymnaea viatrix and Lymnaea columella in the neotropical region: a distributional outline

A review of lymnaeid samples collected by the author from 106 localities in Mexico, Cuba, Jamaica, Haiti, Dominican Republic, Puerto Rico, Martinique, Saint Lucia, Guatemala, Costa Rica, Panamá, Ecuador, Peru, Bolivia, Chile, Argentina, Uruguay andBrazil showed that one of them (from Ecuador) belonged to Lymnaea cousini Jousseaume, 1887, and all the others to either L. viatrix Orbigny, 1835 or l. columella Say, 1817. The ranges of L. viatrix and L. columella overlap in Middle America, and in northern and southern South America (Venezuela-Colombia-Ecuador and northeastern Argentina-Uruguay-southernmost Brazil, respectively). L. viatrix was the only species found in Peru west of the Andes and in Chile, and is supposed to have migrated eastward to Argentina via the Negro river basin. The range of L. columella in South America is discontinuous. The species has been recorded from Venezuela, Colombia and Ecuador and, east of the Andes, from latitudes 15º S (central-west Brazil) to 35º S (La Plata, Argentina). Such a gap may be attributed to either introduction from the northern into the southern area, or migration along the unsampled region on the eastern side of the Andes, or extinction in the now vacant area. No lymnaeids have been found so far in Brazil north of latitude 15º S and in the Guianas.

New specific synonymy in Neotropical Simulium S. L. (Diptera: Simuliidae)

In an attempt to clarify the taxonomy of Neotropical Simuliidae prior to the production of keys to species, various nomenclatural problems are resolved. Information is given on the status of types, their depositories, the condition of type-material where relevant, and on already established synonyms. fifteen new synonyms are established and six lectotypes designated based on an examination of type-material and long series of reared specimens from many localities to take account of intraspecific variation.