Assemblages of drosophilids (Diptera, Drosophilidae) in mangrove forests: community ecology and species diversity

Brazilian fauna of drosophilids has been researched in various ecosystems, but those in mangrove forests remain overlooked in Brazil and elsewhere. The present study attempts to characterise the assemblages of drosophilids of this environment, based on 28 collections taken in three mangrove areas in Santa Catarina Island, southern Brazil. The three mangroves surveyed were different in their surroundings, which varied from highly urbanised areas to conservation areas with natural vegetation. Overall, 69 species were collected, and no remarkable difference was detected in species composition and abundances or in the richness, evenness and heterogeneity between sites. The species abundance distribution observed fitted to a theoretical lognormal distribution in the three mangroves. The species richness scored and the performance of the species richness estimators showed an unexpectedly high diversity, considering the very low floristic diversity and the harsh conditions of the environment. Regarding species composition and abundances, the drosophilid mangrove assemblages were shown to be more similar to those found in open environments, with a marked dominance of exotic species. Finally, considering the apparent lack of feeding and breeding sites, we suggest that mangrove forests are acting as sink habitats for the drosophilids populations.

Impact of fish cage-culture on the community structure of zooplankton in a tropical reservoir

We investigated the impact of fish cage culture on the zooplankton community structure in a tropical reservoir. We hypothesized that community abundance is greater near cages and increases over time due to the increase in food availability. Samplings were performed near, upstream and downstream from net cages, and before and after net cage installation. The abundance of zooplankton increased 15 days after the experiment was set up, followed by a reduction and finally increased. Rotifer abundance showed significant differences among sites (p<0.05) and sampling periods (p<0.001). Significant differences were also observed in total zooplankton and cladoceran abundance (p<0.001). The spatial and temporal variation of the physical and chemical variables were indirectly correlated with the structure and dynamic of the zooplankton community, as they indicated the primary production in the environment. Our hypothesis was rejected, since the zooplankton was abundant at the reference site. Only rotifers showed higher abundance near cages, due to the influence of food availability. Community dynamics during the experiment was also correlated to food availability. Our results suggest an impact of fish farming on the zooplankton community.

Community structure of metazoan parasites of silverside, Odontesthes bonariensis (Pisces, Atherinopsidae) from Argentina

The helminth communities of silverside, Odontesthes bonariensis (Valenciennes, 1835), from two Argentinean lagoons were studied and compared at component community and infracommunity levels. Nine helminth species were found: five digeneans (Austrodiplostomum cf. mordax, Ascocotyle (Phagicola) cf. diminuta, Ascocotyle sp., Thometrema bonariensis and Saccocoelioides sp.); two nematodes (Contracaecum sp. and Hysterothylacium sp.); one acanthocephalan (Wolffhugelia matercula) and one cestode (Cangatiella macdonaghi). Odontesthes bonariensis is a new host record for five parasite species. Richness, diversity and number of helminths in silversides from Salada Grande lagoon were higher than in those from Lacombe lagoon. This could be related with lagoon size, abundance of mollusks and fish-eating birds, and size and diet of silversides captured in each lagoon. In Salada Grande lagoon the helminth community of silversides was dominated by the allogenic and generalist species A. cf. mordax; while the autogenic and intermediate specialist species C. macdonaghi was dominant in Lacombe lagoon. Host sex did not affect richness, diversity or total abundance, whereas host size was positively correlated with these attributes, except diversity in Salada Grande lagoon.

Bird community in an Araucaria forest fragment in relation to changes in the surrounding landscape in Southern Brazil

The dynamics of the bird community in a small forest fragment was evaluated along seven years in relation to changes in the surrounding landscape. The study area is an Araucaria forest fragment in Southern Brazil (state of Paraná). The sampling period covered the years 1988 through 1994 and the mark-release-recapture method was utilized. The landscape analysis was based on Landsat TM images, and changes in exotic tree plantations, native forest, open areas (agriculture, pasture, bare soil, and abandoned field), and "capoeira"(native vegetation < 2 m) were quantified. The relationship between landscape changes and changes in abundance diversity of forest birds, open-area birds, forest-edge birds, and bamboo specialists was evaluated. Richness estimates were run for each year studied. The richness recorded in the study area comprised 96 species. The richness estimates were 114, 118 and 110 species for Chao 1, Jackknife 1 and Bootstrap, respectively. The bird community varied in species richness, abundance and diversity from year to year. As for species diversity, 1991, 1993 and 1994 were significantly different from the other years. Changes in the landscape contributed to the increase in abundance and richness for the groups of forest, open-area and bamboo-specialist species. An important factor discussed was the effect of the flowering of "taquara" (Poaceae), which contributed significantly to increasing richness of bamboo seed eaters, mainly in 1992 and 1993. In general, the results showed that landscape changes affected the dynamics and structure of the bird community of this forest fragment over time, and proved to have an important role in conservation of the avian community in areas of intensive forestry and agricultural activities.

Effects of environmental factors on community structure of Leptophlebiidae (Insecta, Ephemeroptera) in Cerrado streams, Brazil

We analyzed the effects of environmental factors on abundance, species richness, and functional group richness of Leptophlebiidae in 16 sampling points along four Cerrado streams. Across three periods of 2005, we collected 5,492 larvae from 14 species in stream bed substrate. These species belong to three functional feeding groups: scrapers, filtering collectors and shredders. The abundance and species richness were not affected by water quality, but habitat quality related to presence of riparian vegetation had positive effects on the abundance of shredders. Our results add important information on the natural history of the species and functional groups of aquatic insects and also provide relevant data for the monitoring and conservation of streams in the Brazilian Cerrado.

The influence of building materials on the residual action of BHC

Residual insecticide activity of BHC vapors from various building materials in controlled humidity chambers in the laboratory were significantly different. Laboratory-reared, first instar nymphs of Dipetalogaster maximus were exposed to vapors of BHC which were being released from the treated surfaces of building materials taken from Mambaí, Goiás.

Anti-schistosomal drugs: observations on the mechanism of drug resistance to hycanthone, and on the involvement of host antibodies in the mode of action of praziquantel

This paper reports recent observations from our laboratory dealing with the anti-schistosome drugs hycanthone (HC) and praziquantel (PZQ). In particular, we discuss a laboratory model of drug resistance to HC in Schistosoma mansoni and show that drug sensitive and resistant lines of the parasite can be differentiated on the basis of restriction fragment length polymorphisms using homologous ribosomal gene probes. In addition, we summarize data demonstrating that effective chemotherapy of S. mansoni infection with PZQ in mice requires the presence of host anti-parasite antibodies. These antibodies bind to PZQ treated worms and may be involved in an antibody-dependent cellular cytotoxicity reactions which result in the clearance of worms from the vasculature.

Action of colchicine on hepatic schistosomal granuloma

Amorphous material and altered collagen fragments within dilated secretory vesicles and cisternae of fibroblast cytoplasm were the main ultrastructural changes seen in hepatic periovular granulomas formed in mice infected with Schistosoma mansoni and treated with colchicine. Despite promoting ultrastructural changes in the fibroblasts found in hepatic periovular granulomas, colchicine administration to infected mice did not significantly change the light microscopic appearance of the hepatic schistosomal lesions, did not diminish the amount of total hepatic collagen, and did not change the collagen isotypes in the granulomas, as observed after a comparative study with non-colchicine treated infected control mice. When administered to mice two weeks after curative treatment of schistosomiasis with praziquantel, colchicine did not seem to increase extracellular collagen degradation or to induce a more rapid resorption of hepatic periovular granulomas, although still promoting ultrastructura alterations in fibroblasts.

Mechanism of action of a nitroimidazole-thiadiazole derivate upon Trypanosoma cruzi tissue culture amastigotes

Megazol (CL 64,855) a very effective drug in experimental infections by Trypanosoma cruzi, and also in in vitro assays with vertebrate forms of the parasite, had its parasite, had its activity upon macromolecule biosynthesis tested using tissue culture-derived amastigote forms. Megazol presented a drastic inhibition of [3H]-uridine incorporation, suggesting a selective activity upon protein synthesis. Comparing the three drugs, megazol was more potent than nifurtimox and benznidazole in inhibiting protein an DNA synthesis. Megazol showed a 91% of inhibition of [3H]-leucine incorporation whereas nifurtimox and benznidazole, 0% and 2%, respectively. These latter two drugs inhibited the incorporation of all the precursors tested at similar levels, but the concentration of benznidazole was always three times higher, suggesting different mechanisms of action or, more probably, a greater efficiency of the 5-nitrofuran derivate in relation to the 2-nitroimidazole. So, wes conclude that the mode of action of megazol is different from the ones of nifurtimox and benznidazole and that its primary effect is associated with an impairment of protein synthesis.

Toxicological study of the molluscicidal latex of Euphorbia splendens: irritant action on skin and eye

Aqueous solutions of the molluscicidal latex of Euphorbia splendens are irritant to the rabbit eye in concentrations higher than 0.35% and to the rabbit skin in concentrations higher than 0.5%. Although this irritant potential does not proclude its use as a molluscicide, special precautions are recommended for hanbdling and application of the product and the hazard of skin tumor-promoting potencial should be carefully investigated before its use for schistosomiasis vector control.

On the mechanism of protective action of cold acclimatization against carbon tetrachloride - and ethionine-induced fatty liver

In this study the hepatic lipoprotein lipase (LPL), activity was evaluated in adult female mice acclimatized at 5-C and submitted to carbon tetrachloride (CCI) or ethionine, in order to determine the possible role of this enzuyme in the fatty liver. The results were compared with those obtained in mice kept at room temperature (27-C) that the same hepatoesteatosis inducing agent. In contrast to animals kept at room temperature, in cold aclimatized mice neither the enhancement of the LPL-liver activity by the action of CCI or ethionine occurred nor the development of fatty infiltration in the liver was observed. We conclude that the low temperature induced a protective effect against CCI or ethionine-induced fatty liver that was correlated with the no-increase of the hepatic LPL activity.