Life cycle of Triatoma ryckmani (Hemiptera: Reduviidae) in the laboratory, feeding patterns in nature and experimental infection with Trypanosoma cruzi

A cohort initiated with 121 eggs, yielding 105 first instar nymphs (eclosion rate: 86.78%), allowed us to observe the entire life cycle of Triatoma ryckmani under laboratory conditions (24ºC and 62% relative humidity), by feeding them on anesthetized hamsters. It was possible to obtain 62 adults and the cycle from egg to adult took a mean of 359.69 days with a range of 176-529 days (mortality rate of nymphs: 40.95%). Mean life span of adults was of 81 days for females and 148 days for males. The developmental periods of 4th and 5th nymphs were longer than those of the other instars. This suggests that young siblings have a better chance of taking a hemolymph meal from older ones, in order to survive during fasting periods during prolonged absences of vertebrate hosts from natural ecotopes. The stomach contents of 37 insects showed blood from rodents (15 cases), lizards (7 cases), birds (6 cases) and insect hemolymph (7 cases). Out of 10 insects fed by xenodiagnosis on a Trypanosoma cruzi infected mouse, all but one became infected with the parasite.

Short-term therapy with simvastatin reduces inflammatory mediators and heart inflammation during the acute phase of experimental Chagas disease

Trypanosoma cruzi infection induces progressive cardiac inflammation that leads to fibrosis and modifications in the heart architecture and functionality. Statins, such as 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors, have been studied due to their pleiotropic roles in modulating the inflammatory response. Our goal was to evaluate the effects of simvastatin on the cardiac inflammatory process using a cardiotropic strain of T. cruzi in a murine model of Chagas cardiomyopathy. C57BL/6 mice were infected with 500 trypomastigotes of the Colombian strain of T. cruzi and treated with an oral dose of simvastatin (20 mg/Kg/day) for one month and inflammatory and morphometric parameters were subsequently evaluated in the serum and in the heart, respectively. Simvastatin reduced the total cholesterol and inflammatory mediators (interferon-gamma, tumour necrosis factor-alpha, CCL2 and CCL5) in the serum and in the heart tissue at 30 days post-infection. Additionally, a proportional reduction in heart weight and inflammatory infiltration was observed. Simvastatin also reduced epimastigote proliferation in a dose-dependent manner in vitro and was able to reduce blood trypomastigotes and heart amastigote nests during the acute phase of Chagas disease in vivo. Based on these data, we conclude that simvastatin exerts a modulatory effect on the inflammatory mediators that are elicited by the Colombian strain of T. cruzi and ameliorates the heart damage that is observed in a murine model of Chagas disease.

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.

Development of the short version of the informal caregiver burden assessment questionnaire

OBJETIVE to create a reduced version of the QASCI, which is structurally equivalent to the long one and meets the criteria of reliability and validity. METHOD Through secondary data from previous studies, the participants were divided into two samples, one for the development of reduced version and the second for study of the factorial validity. Participants responded to QASCI, the SF 36, the ADHS and demographic questions. RESULTS A reduced version of 14 items showed adequate psychometric properties of validity and internal consistency, adapted to a heptadimensional structure that assesses positive and negative aspects of care. CONCLUSION Confirmatory factor analysis revealed a good fit with the advocated theoretical model.

Biologia de Neotrioza tavaresi Crawford, 1925 (Hemiptera, Psyllidae), galhador da folha do araçazeiro (Psidium cattleianum)

Biology of the leaf gall inducer Neotrioza tavaresi Crawford, 1925 (Hemiptera, Psyllidae) on strawberry guava tree (Psidium cattleianum). A field study was conducted in Curitiba region, State of Paraná, southern Brazil, to describe the life cycle of Neotrioza tavaresi Crawford, 1925, a leaf galling insect in strawberry guava trees (Psidium cattleianum). Three cycles were observed (1997, 1998, 1999) during regular field trips and the insects were observed in Piraquara municipality, where 15 samples with 50 infested leaves were sampled in the 1997-98 cycle. Galls were dissected for detailed studies. Neotrioza tavaresi has a univoltine cycle in which adult individuals were found inside the galls from August onwards. The sexually mature insects with sex ratio 1, emerged from the galls after their dehiscence caused by feeding of the adult insects on the gall walls. Adult emergence started in early October and ended by early December, with its peak in November. Copulation took place as soon as adults exit the gall and egg laying started the next day. Females had more than 100 ovarioles containing 218.7±44.7 (n=50) fully formed eggs. This indicated the short sexual adult life-span (aprox. 5-7 days) of the species, also characterized by a concentrated oviposition. Adult individuals fed and laid their eggs on younger shoots of the plant. The bottoms of the yellowish eggs were inserted into the leaf tissue, mainly on its adaxial edge (78.1%). The nymphs hatched and, as they fed on the adaxial side of expanding leaves, modified the cell growth pattern and the round-shape galls developed on the adaxial side with one insect inside. The gall wall showed distinct layers, with the inner one suppliyng the food to the insects, and the outer layer supplying gall protection. Nymphs went through five instars and the exuviae remained stuck on a ball of wax inside the gall. All parasitoids found were Hymenoptera belonging to Chalcidoidea: Eulophidae (1 sp), Pteromalidae (2 spp) and Encyrtidae (3 spp). The findings suggest that leaf gall inducer and parasitoids insects and plant life cycles are closely connected and both leaf sprouting and gall opening seem to be triggered by the same environmental and plant conditions. The high abundance of shoots may favor insect performance as adult individuals can easily find an ideal place for feeding, copulating and laying eggs.

Life cycle of Phoebemima ensifera Tippmann (Coleoptera, Cerambycidae)

An account of host plant selection, larval development and behaviour, and behaviour of adult Phoebemima ensifera. Illustrations of the host plant, plant parts, larva, pupa, and adult are provided.

Biological cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets of three rubber tree clones

Life cycle of Tenuipalpus heveae Baker (Acari, Tenuipalpidae) on leaflets from three rubber tree clones. The biological cycle of Tenuipalpus heveae Baker, 1945 (Tenuipalpidae), a potential rubber tree pest mite, was studied by the observation of individuals reared on leaflets of the clones GT 1, PB 235 and RRIM 600, in controlled environmental conditions. Three daily observations were done of 60 eggs on leaflets from each clone in order to verify the development of immature stages and the female oviposition. The fertility life table was constructed based in the collected data. Mites reared on PB 235 had faster rate of development, requiring less time in days, to double its population in number (TD), and had the highest values for egg production, female longevity, net reproductive rate (Ro), intrinsic rate of natural increase (r m) and finite rate of increase (λ). Lower reproductive values and the longest time necessary to reach adult stage were recorded for the mites on GT 1. In all studied clones, the deutonymphal phase had the highest viability, while the larval phase had the lowest, highlighted by the survivorship curve that indicated high mortality during this life stage. The clone PB 235 allowed the most suitable conditions for the development of T. heveae, followed by RRIM 600, while GT 1 was the less suitable substratum to rear this mite species.

Colony cycle of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae)

Colony cycle of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae). This study describes some aspects of the colony cycle of the Neotropical social wasp Mischocyttarus consimilis, from data obtained under field conditions. Our results showed that the colony cycle in M. consimilis is annual and asynchronous in relation to the months of the year. The colonies remained active for approximately eight months. Most of the abandonments were associated with natural causes, and were most frequent in the pre-emergence stage. The nests were constructed preferentially in man-made structures, especially in sites protected from direct sunlight and rain. Colony foundation was either by haplometrosis or pleometrosis, being the first form predominant.

Short and long-term effects of tillage systems and nutrient sources on soil physical properties of a Southern Brazilian Hapludox

Soil tillage promotes changes in soil structure. The magnitude of the changes varies with the nature of the soil, tillage system and soil water content and decreases over time after tillage. The objective of this study was to evaluate short-term (one year period) and long-term (nine year period) effects of soil tillage and nutrient sources on some physical properties of a very clayey Hapludox. Five tillage systems were evaluated: no-till (NT), chisel plow + one secondary disking (CP), primary + two (secondary) diskings (CT), CT with burning of crop residues (CTb), and CT with removal of crop residues from the field (CTr), in combination with five nutrient sources: control without nutrient application (C); mineral fertilizers, according to technical recommendations for each crop (MF); 5 Mg ha-1 yr-1 of poultry litter (wetmatter) (PL); 60 m³ ha-1 yr-1 of cattle slurry (CS) and; 40 m³ ha-1 yr-1 of swine slurry (SS). Bulk density (BD), total porosity (TP), and parameters related to the water retention curve (macroporosity, mesoporosity and microporosity) were determined after nine years and at five sampling dates during the tenth year of the experiment. Soil physical properties were tillage and time-dependent. Tilled treatments increased total porosity and macroporosity, and reduced bulk density in the surface layer (0.00-0.05 m), but this effect decreased over time after tillage operations due to natural soil reconsolidation, since no external stress was applied in this period. Changes in pore size distribution were more pronounced in larger and medium pore diameter classes. The bulk density was greatest in intermediate layers in all tillage treatments (0.05-0.10 and 0.12-0.17 m) and decreased down to the deepest layer (0.27-0.32 m), indicating a more compacted layer around 0.05-0.20 m. Nutrient sources did not significantly affect soil physical and hydraulic properties studied.

Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

The ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha-1 y-1 fresh matter of poultry litter; CM = 60 m³ ha-1 y-1 slurry cattle manure; and SM = 40 m³ ha-1 y-1 slurry swine manure) on wet-aggregate stability was determined after nine years (four sampled soil layers) and on five sampling dates in the 10th year (two sampled soil layers) of the experiment. The size distribution of the air-dried aggregates was strongly affected by soil bulk density, and greater values of geometric mean diameter (GMD AD) found in some soil tillage or layer may be partly due to the higher compaction degree. After nine years, the GMD AD on the surface was greater in NT and CP compared to conventional tillage systems (CT, CTb and CTr), due to the higher organic matter content, as well as less soil mobilization. Aggregate stability in water, on the other hand, was affected by the low variation in previous gravimetric moisture of aggregates, which contributed to a high coefficient of variation of this attribute. The geometric mean diameter of water-stable aggregates (GMD WS) was highest in the 0.00-0.05 m layer in the NT system, in the layers 0.05-0.10 and 0.12-0.17 m in the CT, and values were intermediate in CP. The stability index (SI) in the surface layers was greater in treatments where crop residues were kept in the field (NT, CP and CT), which is associated with soil organic matter content. No differences were found in the layer 0.27-0.32 m. The effect of nutrient sources on GMD AD and GMD WS was small and did not affect SI.

Flooded rice yield as affected by levels of water salinity in different stages of its cycle

Losses of productivity of flooded rice in the State of Rio Grande do Sul, Brazil, may occur in the Coastal Plains and in the Southern region due to the use of saline water from coastal rivers, ponds and the Laguna dos Patos lagoon, and the sensibility of the plants are variable according to its stage of development. The purpose of this research was to evaluate the production of rice grains and its components, spikelet sterility and the phenological development of rice at different levels of salinity in different periods of its cycle. The experiment was conducted in a greenhouse, in pots filled with 11 dm³ of an Albaqualf. The levels of salinity were 0.3 (control), 0.75, 1.5, 3.0 and 4.5 dS m-1 kept in the water layer by adding a salt solution of sodium chloride, except for the control, in different periods of rice development: tillering initiation to panicle initiation; tillering initiation to full flowering; tillering initiation to physiological maturity; panicle initiation to full flowering; panicle initiation to physiological maturity and full flowering to physiological maturity. The number of panicles per pot, the number of spikelets per panicle, the 1,000-kernel weight, the spikelet sterility, the grain yield and phenology were evaluated. All characteristics were negatively affected, in a quadratic manner, with increased salinity in all periods of rice development. Among the yield components evaluated, the one most closely related to grain yields of rice was the spikelet sterility.

Soil shear strength under non-irrigated and irrigated short duration grazing systems

Pasture productivity can drop due to soil compaction caused by animal trampling. Physical and mechanical alterations are therefore extremely important indicators for pasture management. The objective of this research was to: draw and evaluate the Mohr failure line of a Red Yellow Latossol under different pasture cycles and natural forest; calculate apparent cohesion; observe possible physical alterations in this soil; and propose a correction factor for stocking rates based on shear strength properties. This study was conducted between March/2006 and March/2007 on the Experimental Farm of Fundação de Ensino Superior de Passos, in Passos, state of Minas Gerais. The total study area covered 6 ha, of which 2 ha were irrigated pasture, 2 ha non-irrigated pasture and 2 ha natural forest. Brachiaria brizantha cv. MG-5 Vitória was used as forage plant. The pasture area was divided into paddocks. The Mohr failure line of samples of a Red Yellow Latossol under irrigated pasture equilibrated at a tension of water content of 6 kPa indicated higher shear strength than under non-irrigated pasture. The shear strength under irrigated pasture and natural forest was higher than under non-irrigated pasture. At a tension of water content of 33 kPa no difference was found in shear strength between management and use. Possible changes in soil structure were caused by apparent cohesion. The values of the correction factor were close to 1, which may indicate a possible soil compaction in prolonged periods of management.

Modeling changes in organic carbon stocks for distinct soils in southeastern brazil after four eucalyptus rotations using the century model

Soil organic matter (SOM) plays an important role in carbon (C) cycle and soil quality. Considering the complexity of factors that control SOM cycling and the long time it usually takes to observe changes in SOM stocks, modeling constitutes a very important tool to understand SOM cycling in forest soils. The following hypotheses were tested: (i) soil organic carbon (SOC) stocks would be higher after several rotations of eucalyptus than in low-productivity pastures; (ii) SOC values simulated by the Century model would describe the data better than the mean of observations. So, the aims of the current study were: (i) to evaluate the SOM dynamics using the Century model to simulate the changes of C stocks for two eucalyptus chronosequences in the Rio Doce Valley, Minas Gerais State, Brazil; and (ii) to compare the C stocks simulated by Century with the C stocks measured in soils of different Orders and regions of the Rio Doce Valley growing eucalyptus. In Belo Oriente (BO), short-rotation eucalyptus plantations had been cultivated for 4.0; 13.0, 22.0, 32.0 and 34.0 years, at a lower elevation and in a warmer climate, while in Virginópolis (VG), these time periods were 8.0, 19.0 and 33.0 years, at a higher elevation and in a milder climate. Soil samples were collected from the 0-20 cm layer to estimate C stocks. Results indicate that the C stocks simulated by the Century model decreased after 37 years of poorly managed pastures in areas previously covered by native forest in the regions of BO and VG. The substitution of poorly managed pastures by eucalyptus in the early 1970´s led to an average increase of C of 0.28 and 0.42 t ha-1 year-1 in BO and VG, respectively. The measured C stocks under eucalyptus in distinct soil Orders and independent regions with variable edapho-climate conditions were not far from the values estimated by the Century model (root mean square error - RMSE = 20.9; model efficiency - EF = 0.29) despite the opposite result obtained with the statistical procedure to test the identity of analytical methods. Only for lower soil C stocks, the model over-estimated the C stock in the 0-20 cm layer. Thus, the Century model is highly promising to detect changes in C stocks in distinct soil orders under eucalyptus, as well as to indicate the impact of harvest residue management on SOM in future rotations.

Nutrient relations during an eucalyptus cycle at different population densities

To synchronize nutrient availability with the requirements of eucalyptus during a cultivation cycle, the nutrient flow of this system must be well understood. Essential, for example, is information about nutrient dynamics in eucalyptus plantations throughout a cultivation cycle, as well as impacts on soil nutrient reserves caused by the accumulation and subsequent export of nutrients via biomass. It is also important to quantify the effect of some management practices, such as tree population density (PD) on these fluxes. Some nutrient relations in an experiment with Eucalyptus grandis, grown at different PDs in Santa Barbara, state of Minas Gerais, Brazil, were evaluated for one cultivation cycle. At forest ages of 0.25, 2.5, 4.5, and 6.75 years, evaluations were carried out in the stands at seven different PDs (between 500 and 5,000 trees ha-1) which consisted in chemical analyses of plant tissue sampled from components of the aboveground parts of the tree, from the forest floor and the litterfall. Nutrient contents and allocations of the different biomass components were estimated. In general, there were only small and statistically insignificant effects of PD on the nutrient concentration in trees. With increasing forest age, P, K, Ca and Mg concentrations were reduced in the aboveground components and the forest floor. The magnitud of biochemical nutrient cycling followed the sequence: P > K > N > Mg. At the end of the cycle, the quantities of N, P, Ca and Mg immobilized in the forest floor were higher than in the other components.

Nutrient extraction and exportation by castor bean hybrid lyra

Information about nutrient extraction and exportation by crops, as well as the periods of highest nutrient demand is important for an adequate fertilization management. However, there are no studies on the nutrient uptake of short-stature hybrid castor bean. Therefore, the purpose of this study was to evaluate nutrient extraction and exportation by short-stature castor bean hybrid Lyra, in the spring-summer and fall-winter growing seasons. The experiments were conducted in the 2005/2006 spring-summer and 2006 fall-winter growing seasons on an Oxisol, in Botucatu, SP, in a randomized block design, with four replications. The plots consisted of plant samplings, which occurred 17, 31, 45, 59, 73, 97 and 120 days after emergence (DAE) in the spring-summer and 17, 31, 45, 59, 80, 100 and 120 DAE in fall-winter growing season. The growth of hybrid Lyra was slow and nutrient uptake lowest between emergence and the beginning of flowering. The period of highest dry matter (DM) accumulation rates and highest nutrient demand were observed 40 to 80 DAE, in both growing seasons. The order of nutrient extraction by the plants in the spring-summer growing season was: N>K>Ca>Mg>S>P>Fe>Mn>Zn>B>Cu>Mo. In fall-winter, S was more absorbed than Mg. Seed yield was higher in the spring-summer (2.995 kg ha-1), but nutrient extraction and exportation per ton of seed were similar in both growing seasons. Around 58 % of N and 84 % of P, and approximately half of the S and B absorbed throughout the cycle were exported with the seeds. However, most of the other nutrients accumulated in the plants returned to the soil in plant residues.