Major shear zones of southern Brazil and Uruguay: escape tectonics in the eastern border of Rio de La plata and Paranapanema cratons during the Western Gondwana amalgamation

The Mantiqueira Province represents a series of supracrustal segments of the South-American counterpart formed during the Gondwana Supercontinent agglutination. In this crustal domain, the process of escape tectonics played a conspicuous role, generating important NE-N-S-trending lineaments. The oblique component of the motions of the colliding tectonic blocks defined the transpressional character of the main suture zones: Lancinha-Itariri, Cubato-Arcadia-Areal, Serrinha-Rio Palmital in the Ribeira Belt and Sierra Ballena-Major Gercino in the Dom Feliciano Belt. The process as a whole lasted for ca. 60 Ma, since the initial collision phase until the lateral escape phase predominantly marked by dextral and subordinate sinistral transpressional shear zones. In the Dom Feliciano Belt, southern Brazil and Uruguay, transpressional event at 630-600 Ma is recognized and in the Ribeira Belt, despite less coevally, the transpressional event occurred between 590 and 560 Ma in its northern-central portion and between ca. 625 and 595 Ma in its central-southern portion. The kinematics of several shear zones with simultaneous movement in opposite directions at their terminations is explained by the sinuosity of these lineaments in relation to a predominantly continuous westward compression.

Population genetic structuring in pacu (Piaractus mesopotamicus) across the Paraná-Paraguay basin: evidence from microsatellites

The Paraná-Paraguay basin encompasses central western Brazil, northeastern Paraguay, eastern Bolivia and northern Argentina. The Pantanal is a flooded plain with marked dry and rainy seasons that, due to its soil characteristics and low declivity, has a great water holding capacity supporting abundant fish fauna. Piaractus mesopotamicus, or pacu, endemic of the Paraná-Paraguay basin, is a migratory species economically important in fisheries and ecologically as a potential seed disperser. In this paper we employ eight microsatellite loci to assess the population structure of 120 pacu sampled inside and outside the Pantanal of Mato Grosso. Our main objective was to test the null hypothesis of panmixia and to verify if there was a different structuring pattern between the Pantanal were there were no physical barriers to fish movement and the heavily impounded Paraná and Paranapanema rivers. All loci had moderate to high levels of polymorphism, the number of alleles varied from three to 18. The average observed heterozygosity varied from 0.068 to 0.911. After the Bonferroni correction three loci remained significant for deviations from Hardy-Weinberg, and for those the frequency of null alleles was estimated. F ST and R ST pairwise comparisons detected low divergence among sampling sites, and differentiation was significant only between Paranapanema and Cuiabá and Paranapanema and Taquari. No correlation between genetic distance and the natural logarithm of the geographic distance was detected. Results indicate that for conservation purposes and for restoration programs small genetic differences detected in the Cuiabá and Paranapanema rivers should be taken in consideration.

O carste no plano de manejo do Parque Estadual Intervales e zona de amortecimento, Estado de São Paulo, Brasil

O Parque Estadual Intervales (PEI) e sua Zona de Amortecimento (ZA), inseridos nos vales dos rios Ribeira de Iguape e Paranapanema, situam-se em domínios de rochas carbonáticas proterozóicas de grande interesse para a mineração, onde se verifica a formação de carste com ocorrência expressiva de cavernas. A caracterização do carste no PEI e ZA para o plano de manejo foi baseada em estudos geológicos e geomorfológicos que permitiram definir o grau de vulnerabilidade à contaminação do aquífero cárstico. As regiões de maior vulnerabilidade do carste no PEI e ZA são aquelas que permitem a introdução direta de contaminantes no aquífero e se caracterizam pela presença de feições cársticas tais como cavernas e sumidouros. Para as regiões onde a recarga ocorre exclusivamente por infiltração difusa e o escoamento superficial converge para rios de superfície, foi associado grau de vulnerabilidade intermediário. Considerando essa análise, foram identificadas áreas com maior potencial para impactos e feitas recomendações para a gestão do parque e sua zona de amortecimento.

Comparative Cytogenetics and Molecular Phylogeography in the Group Astyanax altiparanae - Astyanax aff. bimaculatus (Teleostei, Characidae)

The genus Astyanax comprises small characin fish of the neotropical region. The so-called `yellow-tailed characins` compose one of the most widely distributed Astyanax groups. A. altiparanae and A. aff. bimaculatus, are evolutionarily closely related and commonly found in several Brazilian hydrographic basins. In the present work, chromosomal data of specimens of A. altiparanae and A. aff. bimaculatus from 4 hydrographic basins in the states of Sao Paulo (Upper Tiete, Paranapanema, Ribeira de Iguape) and Rio de Janeiro (Guapimirim) are shown. All the populations showed 50 chromosomes, with different karyotypic formula. Although only a single Ag-NOR bearing chromosome pair was observed, all populations possess multiple cistrons of 18S rDNA. FISH with the 5S rDNA probe showed single signals at the interstitial position of one metacentric chromosome pair. C-bands are distributed in the terminal and interstitial regions of several chromosomes. However, the As-51 satDNA are frugally located in a few chromosomes of fishes from Upper Tiete, Paranapanema and Guapimirim Rivers, being absent in individuals of A. aff. bimaculatus from Ribeira de Iguape River basin. Beside these 4 populations, molecular phylogeography studies were also performed in individuals from Middle and Lower Tiete River basin and from 2 additional collection sites in the Paranapanema and Ribeira de Iguape River basins. The phylogeographic analysis using 2 mtDNA regions (totalizing 1.314 bp of ND2 and ATPase6/8 genes) of 8 populations of the group of `yellow-tailed characins` from 3 major hydrographic basins showed structuring of populations, suggesting a correlation between chromosomal (nuclear) and molecular (mitochondrial) data. Copyright (C) 2011 S. Karger AG, Basel

Revision of the species of the genus Cathorops (Siluriformes: Ariidae) from Mesoamerica and the Central American Caribbean, with description of three new species

The ariid genus Cathorops includes species that occur mainly in estuarine and freshwater habitats of the eastern and western coasts of southern Mexico, Central and South America. The species of Cathorops from the Mesoamerica (Atlantic slope) and Caribbean Central America are revised, and three new species are described: C. belizensis from mangrove areas in Belize; C. higuchii from shallow coastal areas and coastal rivers in the Central American Caribbean, from Honduras to Panama; and C. kailolae from río Usumacinta and lago Izabal basins in Mexico and Guatemala. Additionally, C. aguadulce, from the río Papaloapan basin in Mexico, and C. melanopus from the río Motagua basin in Guatemala and Honduras, are redescribed and their geographic distributions are revised.

Phylogenetic group distribution among Escherichia coli isolated from rivers in Sao Paulo State, Brazil

The phylogenetic group distribution of Escherichia coli strains isolated from the Sorocaba and Jaguari Rivers located in the State of Sao Paulo, Brazil, is described. E. coli strains from group D were found in both rivers while one strain from group B2 was isolated from the Sorocaba river. These two groups often include strains that can cause extraintestinal diseases. Most of the strains analyzed were allocated into the phylogenetic groups A and B1, supporting the hypothesis that strains from these phylogenetic groups are more abundant in tropical areas. Though both rivers are located in urbanized and industrialized areas where the main source of water pollution is considered to derive from domestic sewage, our results suggest that the major sources of contamination in the sampling sites of both rivers might have originated from animals and not humans.

Cárie dentária em população ribeirinha do Estado de Rondônia, Região Amazônica, Brasil, 2005/2006

O objetivo foi analisar experiência de cárie dentária na população ribeirinha residente às margens dos rios Machado e Preto (Rondônia, Brasil), em 2005 e 2006. Foram examinados 469 indivíduos com formulário preconizado pela Organização Mundial da Saúde, sob luz natural e utilização de espátulas de madeira e sonda CPI. Na faixa etária de 4-5 anos de idade, ceod = 4,30 e 19,64% livres de cárie; 6-10 anos, CPOD = 1,04, ceod = 3,52, 17,05% livres de cárie; aos 12 anos, CPOD = 2,65 e 30,76% livres de cárie; aos 18 anos, CPOD = 5,41 e 19,51% livres de cárie; 35-44 anos, CPOD = 17,74 e 2,98% livres de cárie; 65-74 anos, CPOD = 21,56 e 4,34% livres de cárie. Na análise por componentes, constatou-se que o componente cariado tem maior prevalência nas idades de 0-3, 4-5, 6-10, 12 e 18 anos. Em adultos e idosos, o componente que mais contribui é o perdido. Conclui-se que a população apresenta índices de cárie dentária elevados, sendo necessária a atuação em âmbito educativo, preventivo e curativo.

Notas sobre o antigo povoamento indígena do alto Trombetas e Mapuera

A 'Relação' de 1728 de frei Francisco de São Manços, com a narrativa da primeira exploração da bacia Trombetas-Mapuera, no noroeste do Estado do Pará, embora publicada há mais de cem anos, é aqui, pela primeira vez, objeto de análise e de interpretação geográfica e etno-histórica. A importância do documento está em nomear e em localizar com aproximação cerca de 50 'nações' indígenas, quase todas ignoradas pelas fontes históricas e etnográficas posteriores, além de mencionar muitas de suas aldeias e de seus chefes. A reconstituição do itinerário permitiu concluir que a viagem do 'descobridor do Trombetas' transcorreu, na verdade, em grande parte, pelo Mapuera, seu afluente, até o planalto das Guianas. A informação etnográfica, embora limitada, inclui referências a dois níveis de chefia política e à guerra como meio de obter escravos destinados ao escambo por mercadorias.

OSL age determinations of Pleistocene fluvial deposits in Central Amazonia

Absolute dating methods have been used in chronological studies of geological processes and sedimentary units of Quaternary age in Central Amazonia, Brazil. Although radiocarbon dating has been very useful in archaeological research and soil studies, the temporal interval of this method is inefficient in evaluating the sedimentation aspects and geological events from the beginning of the Quaternary in the Amazon basin. The use of crystal luminescence dating has been one of the most promising tool for determining the absolute dating of Quaternary deposits in the Amazonian region. Optically stimulated luminescence (OSL) dating, following the MAR and SAR protocols, in a tectonic-sedimentary study of Quaternary fluvial deposits in the confluence area of the Negro and Solimões rivers, indicated ages from 1.3 (Holocene) to about 67.4 kyears (Late Pleistocene) for these sediments. Low radioactive isotope concentrations were found about 2ppm for 235U and 238U; 5ppm for 232Th; and the 40K concentrations were almost zero. A comparison was made between MAR and SAR protocols taking into account the fluvial depositional process.

Técnicas de extrações e procedimentos de clean-up para a determinação de hidrocarbonetos policílicos aromáticos (HPA) em sedimentos da costa do Ceará

Extraction and clean-up are essential points in polycyclic aromatic hydrocarbon (PAHs) analysis in a solid matrix. This work compares extraction techniques and clean-up procedures for PAH analysis. PAH levels, their toxicological significance and source were also evaluated in the waters of the Cocó and Ceará rivers. The efficiency of PAH recovery was higher for the soxhlet and ultrasonic techniques. PAH recovery varied from 69.3 to 99.3%. Total PAH concentration (ΣHPA) varied from 720.73 to 2234.76 µg kg-1 (Cocó river) and 96.4 to 1859.21 µg kg-1 (Ceará river). The main PAH sources are pyrolytic processes and the levels were classified as medium so that adverse effects are possible.

Revision of the Neotropical trahiras of the Hoplias lacerdae species-group (Ostariophysi: Characiformes: Erythrinidae) with descriptions of two new species

Hoplias lacerdae was originally described from the rio Ribeira de Iguape, Iporanga, São Paulo State. The Hoplias lacerdae group is defined as containing generally large trahiras with the medial margins of dentaries running parallel to each other and lacking teeth on the basihyal compared to the H. malabaricus group in which the medial margins of the dentaries converge towards the mandibular symphysis and which have teeth on the basihyal. A taxonomic revision of the group based on meristic and morphometric data identified five distinct species: H. lacerdae distributed in the rio Ribeira de Iguape and rio Uruguai; H. intermedius from the rio São Francisco, upper rio Paraná basin, and rio Doce; H. brasiliensis from rivers of the Atlantic Coastal drainage from the rio Paraguaçu to the rio Jequitinhonha; H. australis new species, endemic to the rio Uruguai; and H. curupira new species present in northern South America, including the rios Negro, Trombetas, Tapajós, Xingu, Tocantins and Capim in the Amazon basin, upper rio Orinoco near the rio Casiquiare (Venezuela), and coastal rivers of Guyana and Suriname. A lectotype for Hoplias intermedius and a neotype for H. brasiliensis are designated.

Regional scale analysis of landform configuration with base-level (isobase) maps

Base-level maps (or ""isobase maps"", as originally defined by Filosofov, 1960), express a relationship between valley order and topography. The base-level map can be seen as a ""simplified"" version of the original topographic surface, from which the ""noise"" of the low-order stream erosion was removed. This method is able to identify areas with possible tectonic influence even within lithologically uniform domains. Base-level maps have been recently applied in semi-detail scale (e.g., 1:50 000 or larger) morphotectonic analysis. In this paper, we present an evaluation of the method's applicability in regional-scale analysis (e.g., 1:250 000 or smaller). A test area was selected in northern Brazil, at the lower course of the Araguaia and Tocantins rivers. The drainage network extracted from SRTM30_PLUS DEMs with spatial resolution of approximately 900 m was visually compared with available topographic maps and considered to be compatible with a 1:1,000 000 scale. Regarding the interpretation of regional-scale morphostructures, the map constructed with 2nd and 3rd-order valleys was considered to present the best results. Some of the interpreted base-level anomalies correspond to important shear zones and geological contacts present in the 1:5 000 000 Geological Map of South America. Others have no correspondence with mapped Precambrian structures and are considered to represent younger, probably neotectonic, features. A strong E-W orientation of the base-level lines over the inflexion of the Araguaia and Tocantins rivers, suggest a major drainage capture. A N-S topographic swath profile over the Tocantins and Araguaia rivers reveals a topographic pattern which, allied with seismic data showing a roughly N-S direction of extension in the area, lead us to interpret this lineament as an E-W, southward-dipping normal fault. There is also a good visual correspondence between the base-level lineaments and geophysical anomalies. A NW-SE lineament in the southeast of the study area partially corresponds to the northern border of the Mosquito lava field, of Jurassic age, and a NW-SE lineament traced in the northeastern sector of the study area can be interpreted as the Picos-Santa Ines lineament, identifiable in geophysical maps but with little expression in hypsometric or topographic maps.

Lignin phenols used to infer organic matter sources to Sepetiba Bay - RJ, Brasil

Lignin phenols were measured in the sediments of Sepitiba Bay, Rio de Janeiro, Brazil and in bedload sediments and suspended sediments of the four major fluvial inputs to the bay: Sao Francisco and Guandu Channels and the Guarda and Cacao Rivers. Fluvial suspended lignin yields (Sigma 8 3.5-14.6 mgC 10 g dw(-1)) vary little between the wet and dry seasons and are poorly correlated with fluvial chlorophyll concentrations (0.8-50.2 mu gC L(-1)). Despite current land use practices that favor grassland agriculture or industrial uses, fluvial lignin compositions are dominated by a degraded leaf-sourced material. The exception is the Guarda River, which has a slight influence from grasses. The Lignin Phenol Vegetation Index, coupled with acid/aldehyde and 3.5 Db/V ratios, indicate that degraded leaf-derived phenols are also the primary preserved lignin component in the bay. The presence of fringe Typha sp. and Spartina sp. grass beds surrounding portions of the Bay are not reflected in the lignin signature. Instead, lignin entering the bay appears to reflect the erosion of soils containing a degraded signature from the former Atlantic rain forest that once dominated the watershed, instead of containing a significant signature derived from current agricultural uses. A three-component mixing model using the LPVI, atomic N:C ratios, and stable carbon isotopes (which range between -26.8 and -21.8 parts per thousand) supports the hypothesis that fluvial inputs to the bay are dominated by planktonic matter (78% of the input), with lignin dominated by leaf (14% of the input) over grass (6%). Sediments are composed of a roughly 50-50 mixture of autochthonous material and terrigenous material, with lignin being primarily sourced from leaf. (C) 2010 Elsevier Ltd. All rights reserved.

Floristic composition of seasonal riparian forests in Mato Grosso do Sul State, Brazil

(Floristic composition of seasonal riparian forests in Mato Grosso do Sit] State, Brazil). This Study aimed to characterize the floristic composition in two stretches of seasonal semideciduous forest associated with the Formoso River, Bonito, Mato Grosso do Sul State, and in three stretches of seasonal deciduous and semideciduous forests associated with the Salobra, Salobrinha and Perdido rivers in Bodoquena Plateau National Park (76,481 ha) - the only Federal Conservation unit with Integral Protection in the state of Mato Grosso do Sul. The floristic survey was carried out monthly from October/2004 to March/2006, where flowering and fruiting phanerogams were collected by the method of evaluation time. The floristic survey resulted in 56 families, 184 genera and 307 species. Of the total number of species, 68% were trees, 17% shrubs, 14% lianas and only 1% palms. The Fabaceae family (Leguminosae), represented by 51 (16.6%) species, was the most species-rich. These results increase our knowledge of the Mato Grosso do Sul flora and its geographic distribution, thus emphasizing the need for conservation of these riparian forests and providing subsidies for restoration projects of the degraded areas around the conservation unit and permanent protection areas (APPs) of regional rivers.

Cytogenetic characterization of the strongly electric Amazonian eel, Electrophorus electricus (Teleostei, Gymnotiformes), from the Brazilian rivers Amazon and Araguaia

A karyotype analysis of the electric eel, Electrophorus electricus (Teleostei, Gymnotiformes), a strongly electric fish from northern South America, is presented. Two female specimens were analyzed, one from the Amazon River and one from the Araguaia River. The specimens had a chromosomal number of 2n = 52 (42M-SM + 10A). C-bands were present in a centromeric and pericentromeric position on part of the chromosomes; some interstitial C-bands were also present. Heteromorphic nucleolus organizer regions (NORs) were detected in two chromosome pairs of the specimen from the Amazon River. The chromosome number and karyotype characteristics are similar to those of other Gymnotidae species. The genera Electrophorus and Gymnotus are positioned as the basal lineages in the Gymnotiformes phylogeny.