Critical mercury concentration in tropical soils: Impact on plants and soil biological attributes.

Mercury is a toxic element that becomes a problem when present at high concentrations in soils. Mercury toxicity in soils varies depending on chemical species, concentration, exposure routes, and organism vulnerability. There is little information regarding the toxicity of Hg in tropical soils, especially for establishing safe levels of this pollutant. The purpose of this study was to investigate Hg concentrations in two tropical soils and their effect on oats and common beans, as well as on soil biological attributes. The experiment was carried out in a greenhouse, following ISO 11.269-2 and OECD-208 guidelines. Oat and common bean were cultivated in a Typic Hapludox (TyHpx) and Rhodic Acrudox (RhAcx) contaminated with HgCl2 at the following concentrations: 0, 2.5, 5.0, 10.0, 20.0, 40.0, and 80.0 mg of Hg kg-1 of dry soil. The biological variables analyzed were seedling emergence, vegetative growth, chlorophyll content (SPAD index), gas exchange (photosynthetic rate, internal CO2 concentration, transpiration rate, and stomatal conductance), and Hg concentration and accumulation in shoot dry matter. Microbial biomass carbon, soil basal respiration, and metabolic quotient (qCO2) were also analyzed. Due to the sorptive characteristics of TyHpx, it had higher Hg concentrations than RhAcx. Mercury showed toxic effects on both oat and common bean species. However, common bean was affected only at concentrations higher than 20 mg kg-1. The microbial community showed high sensitivity to soil Hg concentrations, but external factors, such as the plant species cultivated, influenced the sensitivity of the community. The microbiota was most sensitive in pots with common bean, and this effect was more pronounced at low clay and low organic matter contents (TyHpx). In this study, the concentration of 0.36 mg kg-1 was critical for Hg in these soils, based on its deleterious effects on oat and common bean and on biological soil attributes.

Two New Species of the Spittlebug Genus Ocoaxo Fennah (Hemiptera: Cercopidae) from Mexico, and Keys for the Groups, Group Three, and First Subgroup.

Insects of the family Cercopidae are known as spittlebugs or froghoppers and are represented by 62 genera in the Neotropical region. One of these genera is Ocoaxo Fennah, 1968 with 30 species. The most recent species to be accepted into this genus, Ocoaxo costaricanus, was described by Nast (Ann Zool 33:93-101, 1975). Herein, two new species of Ocoaxo from Mexico are described. One of these new species forms a complex together with Ocoaxo assimilis (Walker) and Ocoaxo varians (Stål). The complex has economic importance in the mountainous areas of the states of Puebla and Oaxaca because it attacks Pinus spp. and causes a disorder called "pine decline." Additionally, dichotomous keys were designed to identify the Ocoaxo Fennah groups and also the species of the subgroup bivittus.

Selenium and mercury in Brazilian Cerrado soils and their relationships with physical and chemical soil characteristics.

The objective of this study was to determine the natural concentrations of Hg and Se in 45 representative soil profiles from the Cerrado biome in central Brazil, and to correlate their concentrations with soil chemical and physical characteristics. The study area was composed of three sub-regions: Goiás, Northwest of Minas Gerais, and Minas Gerais Triangle. Selenium and Hg concentrations were determined by acid digestion and atomic absorption spectroscopy. Data were subjected to analysis of variance on the means of the Hg and Se variables within each soil class at two depths, followed by multivariate statistical methods. The Hg concentrations ranged from 15 to 182 µg kg-1 and the Se concentrations ranged from 22 to 72 µg kg-1. The soil characteristics that most contributed to Hg concentrations in the soils, according to principal component analysis, were Fe2O3, FeO, TiO2, pH, P2O5, and effective CEC. In general, the soils of the Cerrado biome have deficient Se concentrations. The Humic Rhodic Acrustoxes have Hg concentrations above the prevention reference value for soils of Minas Gerais.

Natural variation of selenium in Brazil nuts and soils from the Amazon region.

Brazil nut tree (Bertholletia excelsa) is native of the Amazon rainforest. Brazil nuts are consumed worldwide and are known as the richest food source of selenium (Se). Yet, the reasoning for such Se contents is not well stablished. We evaluated the variation in Se concentration of Brazil nuts from Brazilian Amazon basin, as well as soil properties, including total Se concentration, of the soils sampled directly underneath the trees crown, aiming to investigate which soil properties influence Se accumulation in the nuts. The median Se concentration in Brazil nuts varied from 2.07 mg kg-1 (in Mato Grosso state) to 68.15 mg kg-1 (in Amazonas state). Therefore, depending on its origin, a single Brazil nut could provide from 11% (in the Mato Grosso state) up to 288% (in the Amazonas state) of the daily Se requirement for an adult man (70 µg). The total Se concentration in the soil also varied considerably, ranging from <65.76 to 625.91 µg kg-1, with highest Se concentrations being observed in soil samples from the state of Amazonas. Se accumulation in Brazil nuts generally increased in soils with higher total Se content, but decreased under acidic conditions in the soil. This indicates that, besides total soil Se concentration, soil acidity plays a major role in Se uptake by Brazil nut trees, possibly due to the importance of this soil property to Se retention in the soil.

Phosphorus improves arsenic phytoremediation by Anadenanthera peregrina by alleviating induced oxidative stress.

Due to similarities in their chemical behaviors, studies examining interactions between arsenic (As)--in special arsenate--and phosphorus (P) are important for better understanding arsenate uptake, toxicity, and accumulation in plants. We evaluated the effects of phosphate addition on plant biomass and on arsenate and phosphate uptake by Anadenanthera peregrina, an important Brazilian savanna legume. Plants were grown for 35 days in substrates that received combinations of 0, 10, 50, and 100 mg kg(-1) arsenate and 0, 200, and 400 mg kg(-1) phosphate. The addition of P increased the arsenic-phytoremediation capacity of A. peregrina by increasing As accumulation, while also alleviating As-induced oxidative stress. Arsenate phytotoxicity in A. peregrina is due to lipid peroxidation, but not hydrogen peroxide accumulation. Added P also increased the activity of important reactive oxygen species-scavenging enzymes (catalase and ascorbate peroxidase) that help prevent lipid peroxidation in leaves. Our findings suggest that applying P represents a feasible strategy for more efficient As phytoremediation using A. peregrina.

Genetic variability of Mahanarva sp (Hemiptera: Cercopidae) collected from different sites in Brazil.

Spittlebugs are the leading cause of damage to tall grasses. Annual losses are estimated to reach 2.1 billion dollars in sugarcane crops and grazing land throughout the world. Correct identification of these species is difficult due to similarities in color, body size and male genitalia. Molecular markers have been useful in the identification and assessment of genetic diversity of many species. We investigated the genetic diversity of the spittlebug species Mahanarva fimbriolata, M. spectabilis and M. liturata and looked for markers that could aid in their identification. DNA from 34 spittlebug specimens, collected from six different regions of Brazil (Brasília, Campo Grande, Valença, Presidente Prudente, Juiz de Fora, and Porto Alegre), was analyzed with 29 RAPD primers, generating 501 polymorphic markers. High genetic variability was found among individuals M. fimbriolata (0.37), M. spectabilis (0.18) and M. liturata (0.69). Species-specific molecular RAPD markers were identified for each of the three species; these could be used as auxiliary tools for their correct identification.

Ocorrência de clastoptera sp. (hemiptera: clastopteridae) danificando a cultura da videira em pernambuco

ABSTRACT This paper describes the occurrence and damages of Clastoptera sp. (Hemiptera: Clastopteridae) in grapevines in Pernambuco State, Brazil. The specimens analyzed in this research were collected in vineyards ( Vitis viniferaL.) in Pernambuco State, in May 2007. The material examined is deposited in the insect collection of Embrapa Uva e Vinho (CEEUV Bento Gonçalves/RS) and Museu de Ciências e Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul (MCTP Porto Alegre, RS). Clastoptera sp., commonly called spittlebug, attacks branches of the grapevine and the rachis of the grapes. The aspect of the attacked area is very characteristic, as the nymphs produce a foam-like spit wherein they are protected. When the attacked branches are young, leaves become dry and when they are older they become chlorotic. The attacked grapes are always discarded, regardless of whether they are for exportation or not, which can cause large economic losses.

RESUMO Este trabalho relata a ocorrência e os danos de Clastoptera sp. (Hemiptera: Clastopteridae) na cultura da videira em Pernambuco, Brasil. Os espécimes foram coletados em vinhedos ( Vitis vinifera L.) no Estado de Pernambuco, em maio de 2007. O material examinado está depositado na Coleção Entomológica da Embrapa Uva e Vinho (CEEUV Bento Gonçalves, RS) e no Museu de Ciências e Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul (MCTP Porto Alegre, RS). A Clastoptera sp., vulgarmente chamada de cigarrinha-da-baba, ataca pecíolos da videira e os engaços dos cachos de uvas. O aspecto da área atacada é muito característico: as ninfas produzem uma espuma com aspecto de cuspo onde ficam protegidas. Quando as brotações atacadas são novas, as folhas ficam secas e quando são mais velhas, ficam cloróticas. Os cachos de uvas atacados são sempre descartados, seja ou não para exportação, o que pode causar grande prejuízo econômico.

Distribution patterns of Neotropical primates (Platyrrhini) based on Parsimony Analysis of Endemicity.

The Parsimony Analysis of Endemicity (PAE) is a method of historical biogeography that is used for detecting and connecting areas of endemism. Based on data on the distribution of Neotropical primates, we constructed matrices using quadrats, interfluvial regions and pre-determinated areas of endemism described for avians as Operative Geographic Units (OGUs). We codified the absence of a species from an OGU as 0 (zero) and its presence as 1 (one). A hypothetical area with a complete absence of primate species was used as outgroup to root the trees. All three analyses resulted in similar groupings of areas of endemism, which match the distribution of biomes in the Neotropical region. One area includes Central America and the extreme Northwest of South America, other the Amazon basin, and another the Atlantic Forest, Caatinga, Cerrado and Chaco.

Distribution patterns of Neotropical primates (Platyrrhini) based on Parsimony Analysis of Endemicity

A Análise de Parcimônia de Endemismo (PAE) é um método da biogeografia histórica que é usado para detectar e conectar áreas de endemismo. Baseando-se em dados de distribuição de primatas Neotropicais, construíram-se matrizes de dados utilizando-se quadrículas, regiões entre rios e áreas de endemismo pré-determinadas para aves como Unidades Geográficas Operacionais (OGUs). Codificou-se a ausência da espécie na OGU como 0 (zero) e a presença como 1 (um). Uma área hipotética com ausência total de espécies de primatas foi usada como grupo externo para polarização. Todas as três análises resultaram em grupos similares de áreas de endemismo, coincidindo com a distribuição de biomas na região Neotropical: uma área incluindo a América Central e o extremo Noroeste da América do Sul; outra, a Bacia Amazônica; e, uma terceira, a Mata Atlântica, Caatinga, Cerrado e Chaco.