An ocellar "pupil" that does not change with light intensity, but with the insect age in Triatoma infestans

The simple eyes (ocelli) of recently emerged adult Triatoma infestans exhibit a narrow elongated "pupil", surrounded by a ring of brown-reddish pigment, the "iris". This pupil does not respond to changes in the illumination, but varies in size after the imaginal ecdysis. This change corresponds, internally, with the growth of the corneal lens and the associated retina up to an age of about 20 days. This has not been previously observed in an insect. The use of this characteristic for recognising young adults of this species is suggested.

Temporal change of the aggregation response in Triatoma infestans

Adults and larvae of Triatoma infestans spend daylight hours assembled in shaded places. An assembling factor has been demonstrated in the excrement of this species. We analysed different aspects of the dynamics of the response of bugs. Recently fed insects do not aggregate around faeces. They start to show a significant assembling response from the 8th hour after feeding onwards. Just deposited faeces do not evoke assembling, but a significant rejection instead. This reaction switches 3 h after deposition, when the faeces become attractive to the insects. The attractiveness of faeces persists for about 10 days and can be recovered after this time by rehydration. These findings are discussed in relation to the biological role of faeces and the dynamics of the use of refuges by T. infestans.

The effects of temperature change on the infection rate of Biomphalaria glabrata with Schistosoma mansoni

The aim of this study was to investigate the influence of temperature on the development of Schistosoma mansoni infections in Biomphalaria glabrata. The snails were infected at 15, 20, and 30ºC, and the cercarial release was analyzed after 30 and 60 days post-infection. Our results showed that a decrease in the temperature has a substantial influence on the development of S. mansoni infection in B. glabrata, with significant differences (p < 0.05) between 15 and 30ºC. These data could provide a better understanding of the epidemiological aspects of schistosomiasis.

An ecoregional classification for the state of Roraima, Brazil: the importance of landscape in malaria biology

Understanding the different background landscapes in which malaria transmission occurs is fundamental to understanding malaria epidemiology and to designing effective local malaria control programs. Geology, geomorphology, vegetation, climate, land use, and anopheline distribution were used as a basis for an ecological classification of the state of Roraima, Brazil, in the northern Amazon Basin, focused on the natural history of malaria and transmission. We used unsupervised maximum likelihood classification, principal components analysis, and weighted overlay with equal contribution analyses to fine-scale thematic maps that resulted in clustered regions. We used ecological niche modeling techniques to develop a fine-scale picture of malaria vector distributions in the state. Eight ecoregions were identified and malaria-related aspects are discussed based on this classification, including 5 types of dense tropical rain forest and 3 types of savannah. Ecoregions formed by dense tropical rain forest were named as montane (ecoregion I), submontane (II), plateau (III), lowland (IV), and alluvial (V). Ecoregions formed by savannah were divided into steppe (VI, campos de Roraima), savannah (VII, cerrado), and wetland (VIII, campinarana). Such ecoregional mappings are important tools in integrated malaria control programs that aim to identify specific characteristics of malaria transmission, classify transmission risk, and define priority areas and appropriate interventions. For some areas, extension of these approaches to still-finer resolutions will provide an improved picture of malaria transmission patterns.

Quantification of the genetic change in the transition of Rhodnius pallescens Barber, 1932 (Hemiptera: Reduviidae) from field to laboratory

Previous studies have reported genetic differences between wild-caught sylvatic, domestic and laboratory pop-ulations of several Triatominae species. The differences between sylvatic and laboratory colonies parallel are similar to the differences observed between sylvatic and domestic populations. Laboratory colonies are frequently used as references for field populations, but the consequences of founder events on the genetic makeup of laboratory or domestic populations are rarely quantified. Our goal was to quantify the genetic change in Rhodnius pallescens populations artificially submitted to founder effects via laboratory colonization. We compared the genetic makeup of two sylvatic populations and their laboratory descendants using a panel of 10 microsatellite markers. Both sylvatic populations were initially collected from palm trees, but the colonies differed in the number of founder insects and amount of time kept in the laboratory. We evaluated allelic polymorphism, differences between expected and observed heterozygosity, estimates of population differentiation (Fst) and inbreeding (Fis, Fit) and cluster analyses based on Nei's distances. We found a unique genetic structure for each sample population, with significant differentiation between the field insects and each of the laboratory generations. These analyses showed strong founder effects and showed that genetic drift had led to a genetic equilibrium over several generations of isolation. Our results suggest that laboratory colonies of R. pallescens have a different genetic structure than their wild relatives and similar processes likely affect other Triatominae laboratory stocks.

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

The effects of artemisinin-based combination therapies (ACTs) on transmission of Plasmodium falciparum were evaluated after a policy change instituting the use of ACTs in an endemic area. P. falciparum gametocyte carriage, sex ratios and inbreeding rates were examined in 2,585 children at presentation with acute falciparum malaria during a 10-year period from 2001-2010. Asexual parasite rates were also evaluated from 2003-2010 in 10,615 children before and after the policy change. Gametocyte carriage declined significantly from 12.4% in 2001 to 3.6% in 2010 (@@χ² for trend = 44.3, p < 0.0001), but sex ratios and inbreeding rates remained unchanged. Additionally, overall parasite rates remained unchanged before and after the policy change (47.2% vs. 45.4%), but these rates declined significantly from 2003-2010 (@@χ² for trend 35.4, p < 0.0001). Chloroquine (CQ) and artemether-lumefantrine (AL) were used as prototype drugs before and after the policy change, respectively. AL significantly shortened the duration of male gametocyte carriage in individual patients after treatment began compared with CQ (log rank statistic = 7.92, p = 0.005). ACTs reduced the rate of gametocyte carriage in children with acute falciparum infections at presentation and shortened the duration of male gametocyte carriage after treatment. However, parasite population sex ratios, inbreeding rates and overall parasite rate were unaffected.

Change in mutation patterns of Plasmodium vivax dihydrofolate reductase (Pvdhfr) and dihydropteroate synthase (Pvdhps) in P. vivax isolates from malaria endemic areas of Thailand

Malaria is the most important public health problem in several countries. In Thailand, co-infections of Plasmodium vivax and Plasmodium falciparum are common. We examined the prevalence and patterns of mutations in P. vivax dihydrofolate reductase (Pvdhfr) and P. vivax dihydropteroate synthase (Pvdhps) in 103 blood samples collected from patients with P. vivax infection who had attended the malaria clinic in Mae Sot, Tak Province during 2009 and 2010. Using nested polymerase chain reaction-restriction fragment length polymorfism, we examined single nucleotide polymorphisms-haplotypes at amino acid positions 13, 33, 57, 58, 61, 117 and 173 of Pvdhfr and 383 and 553 of Pvdhps. All parasite isolates carried mutant Pvdhfr alleles, of which the most common alleles were triple mutants (99%). Eight different types of Pvdhfr and combination alleles were found, as follows: 57I/58R/117T, 57I/58R/117T, 57I/58R/117T/N, 57L/58R/117T, 57L/58R/117T, 58R/61M/117N, 58R/61M/117N and 13L/57L/58R/117T. The most common Pvdhfr alleles were 57I/58R/117T (77.7%), 57I/58R/117T/N (1%), 57L/58R/117T (5.8%) and 58R/61M/117N (14.5%). The most common Pvdhfr alleles were 57I/58R/117T (77.7%), 57I/58R/117T/N (1%), 57L/58R/117T (5.8%) and 58R/61M/117N (14.5%). Additionally, we recovered one isolate of a carrying a quadruple mutant allele, 13L/57L/58R/117T. The most prevalent Pvdhps allele was a single mutation in amino acid 383 (82.5%), followed by the wild-type A383/A553 (17.5%) allele. Results suggest that all P. vivax isolates in Thailand carry some combination of mutations in Pvdhfr and Pvdhps. Our findings demonstrate that development of new antifolate drugs effective against sulfadoxine-pyrimethamine-resistant P. vivax is required.

Stratigraphical discontinuities, tropical landscape evolution and soil distribution relationships in a case study in SE-Brazil

On a regional summit surface in the county of Piracicaba (SP) within the Peripheric Depression of São Paulo, formed of discontinued flattened tops, there is an abrupt transition between a Typic Hapludox and a Kandiudalfic Eutrudox, together with two stoneline layers. Using stratigraphical, mineralogical, and cartographic studies, this transition and the soil distribution of this surface were studied, correlating them with the different parent materials and the morphoclimatic model of landscape evolution in Southeastern Brazil. The Typic Hapludox was formed on a sandy Cenozoic deposit (Q) that overlies a pellitic deposit of the Iratí formation (Pi), representing a regional erosive discordance. Westwards to the Piracicaba River, this sequence is interrupted by a diabase sill overlain by a red clayey material which gave origin to the Kandiudalfic Eutrudox. Two post-Permian depositional events were identified by the two stonelines and stratigraphical discontinuities. The first event generated the deposition of a sandy sediment in the form of levelled alveoluses on regional barriers, most of these formed by dikes and diabase sills, probably during a drier phase. The second depositional event, leading to the deposition of the red clay was probably the dissection of the previously formed pediplane during a humid climate, followed by another pedimentation process during a later, drier period.

Geoecological drivers of cerrado heterogeneity and 13C natural abundance in oxisols after land-use change

The 13C natural abundance technique was applied to study C dynamics after land-use change from native savanna to Brachiaria, Pinus, and Eucalyptus in differently textured Cerrado Oxisols. But due to differences in the d13C signatures of subsoils under native savanna and under introduced species, C substitution could only be calculated based on results of cultivated soils nearby. It was estimated that after 20 years, Pinus C had replaced only 5 % of the native C in the 0-1.2 m layer, in which substitution was restricted to the top 0.4 m. Conversely, after 12 years, Brachiaria had replaced 21 % of Cerrado C to a depth of 1.2 m, where substitution decreased only slightly throughout the entire profile. The high d13C values in the subsoils of the cultivated sites led to the hypothesis that the natural vegetation there had been grassland rather than Cerrado sensu stricto, in spite of the comparable soil and site characteristics and the proximity of the studied sites. The hypothesis was tested using aerial photographs of 1964, which showed that the cultivated sites were located on a desiccated runoff head. The vegetation shift to a grass-dominated savanna formation might therefore have occurred in response to waterlogging and reduced soil aeration. A simple model was developed thereof, which ascribes the different Cerrado formations mainly to the plant-available water content and soil aeration. Soil fertility is considered of minor significance only, since at the studied native savanna sites tree density was independent of soil texture or nutrient status.

Highlands of the upper Jequitinhonha valley, Brazil: II - mineralogy, micromorphology, and landscape evolution¹

Palm swanp formations, the so-called veredas, typically occur in the Brazilian biome known as "Cerrado" (savanna-like vegetation), especially on flattened areas or tablelands (chapadas). The aim of this study was to characterize the mineralogy and micromorphology of soil materials from a representative toposequence of the watershed of the vereda Lagoa do Leandro, located in Minas Novas, state of Minas Gerais, Brazil, on plains in the region of the upper Jequitinhonha valley, emphasizing essential aspects of their genesis and landscape evolution. The toposequence is underlain by rocks of the Macaúbas group and covered with detrital and metamorphic rocks (schists of Proterozoic diamictites). The soil profiles were first pedologically described; samples of the disturbed and undisturbed soils were collected from all horizons for further micromorphological and mineralogical analyses. The mineralogical analysis was mainly based on powder X ray diffractometry (XRD) and micromorphological descriptions of thin sections under a petrographic microscope. The soils from the bottom to the top of this toposequence were classified as: Typic Albaquult (GXbd), Xanthic Haplustox, gray color, here called "Gray Haplustox" ("LAC"), Xanthic Haplustox (LA) and Typic Haplustox (LVA). The clay mineralogy of all soils was found to be dominated by kaolinite. In soil of LA and LVA, the occurrence of goethite, gibbsite, and anatase was evidenced; "LAC" also contained anatase and the GXbd, illite, anatase, and traces of vermiculite. The micromorphological analyses of the LVA, LA and "LAC" soils showed the prevalence of a microaggregate-like or granular microstructure, and aggregate porosity has a stacked/packed structure, which is typical of Oxisols. A massive structure was observed in GXbd material, with the presence of illuviation cutans of clay minerals and iron compounds. Paleogleissolos, which are strongly weathered, due to the action of the excavating fauna , and resulted in the present "LAC". The GXbd at the base of the vereda preserved the physical, mineralogical and micromorphological properties that are typical of a pedogenesis with a strong influence of long dry periods.

Magnetic susceptibility to identify landscape segments on a detailed scale in the region of Jaboticabal, São Paulo, Brazil

The agricultural potential is generally assessed and managed based on a one-dimensional vision of the soil profile, however, the increased appreciation of sustainable production has stimulated studies on faster and more accurate evaluation techniques and methods of the agricultural potential on detailed scales. The objective of this study was to investigate the possibility of using soil magnetic susceptibility for the identification of landscape segments on a detailed scale in the region of Jaboticabal, São Paulo State. The studied area has two slope curvatures: linear and concave, subdivided into three landscape segments: upper slope (US, concave), middle slope (MS, linear) and lower slope (LS, linear). In each of these segments, 20 points were randomly sampled from a database with 207 samples forming a regular grid installed in each landscape segment. The soil physical and chemical properties, CO2 emissions (FCO2) and magnetic susceptibility (MS) of the samples were evaluated represented by: magnetic susceptibility of air-dried fine earth (MS ADFE), magnetic susceptibility of the total sand fraction (MS TS) and magnetic susceptibility of the clay fraction (MS Cl) in the 0.00 - 0.15 m layer. The principal component analysis showed that MS is an important property that can be used to identify landscape segments, because the correlation of this property within the first principal component was high. The hierarchical cluster analysis method identified two groups based on the variables selected by principal component analysis; of the six selected variables, three were related to magnetic susceptibility. The landscape segments were differentiated similarly by the principal component analysis and by the cluster analysis using only the properties with higher discriminatory power. The cluster analysis of MS ADFE, MS TS and MS Cl allowed the formation of three groups that agree with the segment division established in the field. The grouping by cluster analysis indicated MS as a tool that could facilitate the identification of landscape segments and enable the mapping of more homogeneous areas at similar locations.

Artificial neural networks applied for soil class prediction in mountainous landscape of the Serra do Mar¹

Soil information is needed for managing the agricultural environment. The aim of this study was to apply artificial neural networks (ANNs) for the prediction of soil classes using orbital remote sensing products, terrain attributes derived from a digital elevation model and local geology information as data sources. This approach to digital soil mapping was evaluated in an area with a high degree of lithologic diversity in the Serra do Mar. The neural network simulator used in this study was JavaNNS and the backpropagation learning algorithm. For soil class prediction, different combinations of the selected discriminant variables were tested: elevation, declivity, aspect, curvature, curvature plan, curvature profile, topographic index, solar radiation, LS topographic factor, local geology information, and clay mineral indices, iron oxides and the normalized difference vegetation index (NDVI) derived from an image of a Landsat-7 Enhanced Thematic Mapper Plus (ETM+) sensor. With the tested sets, best results were obtained when all discriminant variables were associated with geological information (overall accuracy 93.2 - 95.6 %, Kappa index 0.924 - 0.951, for set 13). Excluding the variable profile curvature (set 12), overall accuracy ranged from 93.9 to 95.4 % and the Kappa index from 0.932 to 0.948. The maps based on the neural network classifier were consistent and similar to conventional soil maps drawn for the study area, although with more spatial details. The results show the potential of ANNs for soil class prediction in mountainous areas with lithological diversity.