Temporal dynamics of two species of Chaetophoraceae (Chlorophyta) in tropical streams of São Paulo State, Southeastern Brazil

Temporal dynamics of the chaetophoracean green algae Chaetophora elegans (Roth) C.A. Agardh and Stigeoclonium amoenum Kützing populations was investigated biweekly during late autumn trhough early spring (April to October) in two tropical streams from northwestern São Paulo State, southeastern Brazil. Abundances of one population of each species was evaluated by the quadrat technique in terms of percent cover and frequency. The fluctuations were related to the following stream variables: temperature, turbidity, specific conductance, pH, oxygen saturation, depth, substratum type, current velocity, irradiance and nutrients. Percent cover and frequency of C. elegans had lower values throughout the study period and was positively correlated to rainfall. Other correlations (i.e. positive of percent cover with depth and current velocity and negative with irradiance) were consistently found, reinforcing the strong influence of rainfall. On the other hand, percent cover and frequency of S. amoenum had higher values, with maximum growth from June to September. Percent cover was negatively correlated to rainfall. Results suggest the precipitation regime as the most important driving force to temporal changes in both populations, but playing different roles in each one. The gelatinous thallus of C. elegans seem to be favored by the increment of current velocity, since higher flows can improve the nutrient uptake by means of reduction in diffusion shell without promoting excessive drag force. In contrast, tufts of S. amoenum are, presumably, more exposed to drag force, and, consequently, more susceptible to mechanical damage effects due to higher current velocities.

Imported and autochthonous cases in the dynamics of dengue epidemics in Brazil

OBJECTIVE: To estimate the basic reproduction number (R0) of dengue fever including both imported and autochthonous cases. METHODS: The study was conducted based on epidemiological data of the 2003 dengue epidemic in Brasília, Brazil. The basic reproduction number is estimated from the epidemic curve, fitting linearly the increase of initial cases. Aiming at simulating an epidemic with both autochthonous and imported cases, a "susceptible-infectious-resistant" compartmental model was designed, in which the imported cases were considered as an external forcing. The ratio between R0 of imported versus autochthonous cases was used as an estimator of real R0. RESULTS: The comparison of both reproduction numbers (only autochthonous versus all cases) showed that considering all cases as autochthonous yielded a R0 above one, although the real R0 was below one. The same results were seen when the method was applied on simulated epidemics with fixed R0. This method was also compared to some previous proposed methods by other authors and showed that the latter underestimated R0 values. CONCLUSIONS: It was shown that the inclusion of both imported and autochthonous cases is crucial for the modeling of the epidemic dynamics, and thus provides critical information for decision makers in charge of prevention and control of this disease.

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina: III. Persistence of T. cruzi parasitemia among canine reservoirs in a two-year follow-up

A new cross-sectional survey of household- associated mongrel dogs as well as follow-up of previously parasitemic individuals was carried out in 1984 toy means of xenodiagnosis and serologic techniques to get a deeper insight into the relationship of T. cruzi parasitemia and age among canine hosts in a rural area of Argentina. Persistence of detectable parasitemia was age-independent, or at most, loosely related to age, confirming the pattern observed in 1982. Similarly no significant age-decreasing effect was recorded among seropositive dogs in: a) the probability of detecting parasites in a 2-year follow-up; b) their intensity of infectiousness (=infective force) for T. infestans 3rd-4th instar nymphs, as measured by the percentage of infected bugs observed in each dog xenodiagnosis. Moreover, not only was the infective force of seropositive dogs for bugs approximately constant through lifetime, but it was significantly higher than the one recorded for children in the present survey, and for human people by other researchers. Therefore, and since T. infestans field populations show high feeding frequencies on dogs, the latter are expected to make the greatest contribution to the pool of infected vectors in the rural household of Argentina. This characteristic should be sufficient to involve canine reservoirs definitely as a risk factor for human people residing in the same house. The increased severity of parasitemia observed among dogs in this survey may be related to the acute undernutrition characteristic of canine populations of poor rural areas in our country, which is expected to affect the ability of the host to manage the infection.

DETECTION OF IgM ANTIBODIES TO Schistosoma mansoni GUT-ASSOCIATED ANTIGENS FOR THE STUDY OF THE DYNAMICS OF SCHISTOSOMIASIS TRANSMISSION IN AN ENDEMIC AREA WITH LOW WORM BURDEN

For a period of 2 years, five follow-up measures of prevalence and incidence rates were estimated in a prospective study of S. mansoni infection in a group of schoolchildren who were living in a rural area of the Municipality of Itariri (São Paulo, Brazil), where schistosomiasis is transmitted by Biomphalaria tenagophila. Infection was determined by the examination of three Kato-Katz stool slides, and the parasitological findings were analyzed in comparison to serological data. In the five surveys, carried out at 6-month intervals (March-April and September-October), the prevalences were, respectively, 8.6, 6.8, 9.9, 5.8 and 17.2% by the Kato-Katz, and 56.5, 52.6, 60.8, 53.5 and 70.1% by the immunofluorescence test (IFT). Geometric mean egg counts were low: 57.8, 33.0, 35.6, 47.3 and 40.9 eggs per gram of feces, respectively. Of the total of 299 schoolchildren, who submitted five blood samples at 6-month intervals, one for each survey, 40% were IFT-positive throughout the study, and 22% were IFT-negative in all five surveys. Seroconversion from IFT negative to positive, indicating newly acquired S. mansoni infection, was observed more frequently in surveys carried out during March-April (after Summer holidays), than during September-October. Seasonal trends were not statistically significant for detection of S. mansoni eggs in stool. The results indicate that the use of IgM-IFT is superior to parasitological methods for detection of incidence of S. mansoni infection in areas with low worm burden.

Dynamics of Capillaria-hepatica-induced hepatic septal fibrosis in rats

INTRODUCTION: The pathogenesis of septal hepatic fibrosis, induced in rats by Capillaria hepatica infection, was studied with the aid of a large collection of stored paraffin blocks, representative of the different evolutive phases of fibrosis which appeared in 100% of infected rats. METHODS: Studies were conducted involving histology, immunohistochemistry, immunofluorescence and morphometric methods, in order to observe the dynamic behavior of the cellular and matrix components of fibrosis, over a one year period of evolution. RESULTS: Observation verified that septal fibrosis originates from several portal spaces simultaneously. Its origin and progression involve blood vessel proliferation (angiogenesis), multiplication of actin-positive cells (pericytes and myofibroblasts) and progressive collagen deposition. By the end of 4-5 months, a progressive decrease in all these components was observed, when signs of regression of septal fibrosis became more evident over time. CONCLUSIONS: Besides indicating the fundamental role played by angiogenesis in the pathogenesis of fibrosis, these morphological data concerning the dynamics of this C. hepatica experimental model proved to be adequate for future investigations regarding the functional aspects of fibrosis induction, progression and regression.

Spatial dynamics of urban populations of Lutzomyia longipalpis (Diptera: Psychodidae) in Caxias, State of Maranhão, Brazil

Introduction In this paper, we report the ecology of Lutzomyia longipalpis in Caxias City, located in the eastern part of State of Maranhão, Brazil and highlight its seasonal and geographical distribution by environment. In addition, we discuss natural Leishmania infection and its relationship with visceral leishmaniasis. Methods Between September 2007 and August 2009, the collection of sandflies was performed using Center for Disease Control (CDC) light traps from 15 houses in 5 selected neighborhoods. Results Lutzomyia longipalpis was present in all zones of the city. We also found that Lu. longipalpis was regularly detected both inside and around the house, predominantly in outdoor areas. In urban areas, Lu. longipalpis was present in both the dry and rainy seasons, with a higher density present in the latter. One female specimen of Lu. longipalpis was observed to have natural Leishmania infection. Conclusions The presence of Lu. longipalpis was observed throughout the year during 2 seasonal periods, with a predominance in the rainy season. A low rate of natural Leishmania infection was observed in urban areas during the rainy season.

Schistosomiasis mansoni in urban Northeast Brazil: influence of rainfall regime on the population dynamics of Biomphalaria sp.

Introduction Our objective was to evaluate the influence of rainfall regime on the population dynamics of Biomphalaria in a potential urban focus of schistosomiasis in Aracaju, Brazil, during 2009-2010. Methods Snails were collected monthly and were counted, measured and identified; the level of infection and fecal contamination at the sampling sites was determined; rainfall data were obtained. Results High levels of fecal contamination were observed, and the abundance of Biomphalaria glabrata increased during the rainy and post-rainy seasons. The snails' size was variable, and infected snails were identified independently of rainfall. Conclusions These results provide evidence of anthropogenic and climate interference in an urban focus of schistosomiasis in the Aracaju metropolitan area.

Diversity and dynamics of airborne fungi in São Luis, State of Maranhão, Brazil

Introduction: This study aimed to identify airborne fungi in São Luis, Maranhão, Brazil, to determine the prevalent genera and to correlate these genera with the area and season. Methods: In total, 1,510 colony-forming units (CFUs) of airborne fungi were isolated from the north, south, east and west sides and from the center of the city from January to December 2007. The samples were collected on Petri dishes that were exposed to the fungi by the gravitational method. Results: Twenty genera of fungi were isolated; the most common were Aspergillus (33.5%), Penicillium (18.8%), Cladosporium (14.2%), Curvularia (10.6%) and Fusarium (7.6%). The CFUs of the fungi were statistically significant (p < 0.0001). Fungal biological diversity was present all year, without any large seasonal variations but with slight increases in May, August and September. Conclusions: The fungal genera identified in this study were correlated with natural systems and could be useful when evaluating the impact of environmental changes on the region.

Observations on dynamics of foraging hole construction of two leaf-feeding, soil-inhabiting Syntermes species (insecta: Isoptera) in an Amazonian Rainforest, Brazil

The intensity of construction of foraging access holes by two leaf-litter feeding, soil- inhabiting termite species, Syntermes molestus and Syntermes spinosus, in a Central Amazonian rain forest, was observed on consecutive nights for two weeks. Between 11 and 48 nest entrances per m2 were counted. Interaction between the two species was intense; some entrance holes were overtaken by the larger species during the observations; however, both species coexist in the area. A calculated minimum of 35 entrances/m2 is built every year by both species, emphasizing the importance of soil-burrowing termites for soil structure, aeration and water regime.

Flood pulse and spatial dynamics of mercury in sediments in Puruzinho lake, Brazilian Amazon

The study was conducted in Puruzinho lake (Humaitá, AM) considering seasonal periods of rainy and dry in way to elucidate the flood pulse importance in the deposition, remobilization and distributions of mercury and organic matter in bottom sediments in the Madeira River Basin (Brazilian Amazon). Bottom sediments and soils samples were analyzed for total mercury and organic matter. Mercury concentrations obtained in bottom sediment were 32.20-146.40 ng g-1 and organic matter values were 3.5 - 18.0%. The main region for accumulation of mercury and organic matter was in the central and deepest lake area In the rainy season there was a greater distribution of Hg and organic matter, mainly controlled by means of income of the Madeira river water during flooding, while the predominant process in the dry season was the remobilization of total Hg due to the resuspension of bottom sediments.

Seasonal dynamics of a drosophilid (Diptera) assemblage and its potencial as bioindicator in open environments

Drosophila Fallen, 1823 (Diptera, Drosophilidae) is for long a well-established model organism for genetics and evolutionary research. The ecology of these flies, however, has only recently been better studied. Recent papers show that Drosophila assemblies can be used as bioindicators of forested environment degradation. In this work the bioindicator potential of drosophilids was evaluated in a naturally opened environment, a coastal strand-forest (restinga). Data from nine consecutive seasonal collections revealed strong temporal fluctuation pattern of the majority of Drosophila species groups. Drosophila willistoni group was more abundant at autumns, whereas D. cardini and D. tripunctata groups were, respectively, expressive at winters and springs, and D. repleta group at both seasons. The exotic species D. simulans Sturtevant, 1919 (from D. melanogaster group) and Zaprionus indianus Gupta, 1970 were most abundant at summers. Overall, the assemblage structure did not show the same characteristics of forested or urban environments, but was similar to the forests at winters and to cities at summers. This raises the question that this locality may already been under urbanization impact. Also, this can be interpreted as an easily invaded site for exotic species, what might lead to biotic homogenization and therefore can put in check the usage of drosophilid assemblages as bioindicators at open environments.

Population dynamics of the pea crab Austinixa aidae (Brachyura, Pinnotheridae): a symbiotic of the ghost shrimp Callichirus major (Thalassinidea, Callianassidae) from the southwestern Atlantic

The Pinnotheridae family is one of the most diverse and complex groups of brachyuran crabs, many of them symbionts of a wide variety of invertebrates. The present study describes the population dynamics of the pea crab Austinixa aidae (Righi, 1967), a symbiont associated with the burrows of the ghost shrimp Callichirus major (Say, 1818). Individuals (n = 588) were collected bimonthly from May, 2005 to September, 2006 along a sandy beach in the southwestern Atlantic, state of São Paulo, Brazil. Our data indicated that the population demography of A. aidae was characterized by a bimodal size-frequency distribution (between 2.0 and 4.0 mm and between 8.0 and 9.0 mm CW) that remained similar throughout the study period. Sex ratio does not differ significantly from 1:1 (p > 0.05), which confirms the pattern observed in other symbiontic pinnotherids. Density values (1.72 ± 1.34 ind. • ap.-1) are in agreement with those found for other species of the genus. The mean symbiosis incidence (75.6%) was one of the highest among species of the Pinnotheridae family, but it was the lowest among the three studied species of the genus. Recruitment pattern was annual, beginning in May and peaking in July, in both years, after the peak of ovigerous females in the population (from March to May). Our findings describe ecological and biological aspects of A. aidae similar to those of other species of this genus, even from different geographic localities.

Morphology and dynamics of male gametogenesis in Sympterygia bonapartii (Chondrichthyes, Rajidae) from Northern Patagonia

ABSTRACT The smallnose fanskate, Sympterygia bonapartii Müller & Henle, 1841 is one of the most disembarked items in commercial harbors in Argentina. In this work, the microscopic architecture of mature male gonads and the dynamics of cysts development are analyzed as a contribution to awareness of the reproductive biology of the species. Some biological data related to reproduction are given as well. Two seasons were sampled (fall and spring) and length classes's frequency distribution and maturity stages frequency distribution are given. Size at first sexual maturation for males was estimated at 57 cm of total length. Testes are symmetric, peer, lobed, with several germinal zones. Inside the gonads, there are many spermatocysts, containing reproductive cells at the same developmental stage. On the basis of their cytological and microanatomical features, several maturative degrees of the spermatogenic series were differentiated. Few Leydig cells were recognized at the interstitial tissue among cysts. The microscopic and semiquantitative analysis performed in this work provides morphological information about male gametogenesis and some biological data for the North Patagonian population of this economically and ecologically important species.

Population dynamics of aquatic snails in Pampulha reservoir

An attempt was made to determine more accurately the density of molluskan populations in the Pampulha reservoir, using the quadrate method, intending to detect the fluctuation of the populations density, the habitat conditions and the possible competitive interactions among Biomphalaria tenagophila, Melanoides tuberculata, Pomacea haustrum and Biomphalaria glabrata, through the analysis of populational parameters. Among the most significative facts observed in the reservoir it has to be mentioned: the almost disappearance of B. glabrata; the invasion, colonization, fixation and fast growing of M. tuberculata population until reaching about 11,000 individuals/[square metre]; the density fluctuations of B. tenagophila, P. haustrum and M. tuberculata alives and deads; differences on the habitat preference of these three molluskan species at the edge (at the limit earth-water, at 0.70m and 1.40m from the shore line); monthly mortality rates and reproduction seasons of the species.

Dynamics of fibrosis production and resorption in intestinal schistosomiasis of mice

A histological, morphometric and immunocytochemical study of schistosomal periovular granulomas in the liver and intestines of mice revealed that intestinal granulomas are smaller and contain less collagen than those in the liver. After curative treatment intestinal granulomas undergo a relatively more rapid resorption, although the general pattern of collagen degradation apparently does not differ from that observed in the liver. Tendency to form scattered, usually isolated granulomas that are only mildly fibrogenic, coupled with a well-balanced process of resorption appear as the explanation why intestinal fibrosis is not an outstanding feature of schistosomiasis as it is in the liver.