ABSTRACT We investigated the infestation by Octolasmis lowei Darwin, 1851 in branchial chambers of the portunid Achelous spinimanus (Latreille, 1819), Arenaeus cribrarius (Lamarck, 1818), Callinectes danae Smith, 1869, and Callinectes ornatus Ordway, 1863. We evaluated how infestation is related to host maturity, molt stage, carapace width and sex. The infestation probability increases with host carapace width, and infested crabs were more likely to be adults in intermolt stage. Infestation prevalence did not differ between sexes, except for C. ornatus, in which females had higher infestation than males. Infestation intensity was higher for males than females in A. cribrarius and A. spinimanus, while C. ornatus showed an opposite pattern. Association of O. lowei with portunid seems to be tightly related to the biological traits of its host. Some of these traits, such as host size, maturity and molt stage, are likely to affect infestation in a similar way for all host species, while the effect of other traits, such as sex identity, seems to vary among hosts. We suggest a deeper understanding of the factors driving host use by generalist epibionts such as O. lowei depends on investigating their occurrence on a variety of potential hosts, as well as performing manipulative studies to evaluate the factors driving host preferences by this epibiont.

Na região da campanha gaúcha no sudoeste do Estado do Rio Grande do Sul existem áreas que demonstram fragilidade em relação às características climáticas e pedológicas. Os areais da região têm despertado especial atenção nas últimas décadas devido a questões históricas, socioeconômicas e ambientais. O processo de arenização origina-se da dinâmica de fenômenos naturais como precipitações e ventos. Dessa forma, a dinâmica da arenização poderia ser influenciada por uma tendência positiva no aumento das precipitações nesta região. O objetivo desse trabalho foi analisar as precipitações para diferentes escalas de tempo em Alegrete (RS) de 1928-2009 na identificação de possíveis evidências de modificações no seu comportamento. Foram utilizados dados pluviométricos de postos da Agência Nacional de Águas, disponibilizados pelo sistema hidroweb (http://hidroweb.ana.gov.br). Após organizar os dados (em escalas de tempo mensal, trimestral e anual), os mesmos foram analisados em relação a sua tendência linear ao longo do tempo. A aplicação do Teste de Mann-Kendall permitiu avaliar qualitativamente as tendências encontradas (positivas e negativas), no entanto, não puderam ser consideradas como evidências de modificação climática, mas sim, como comportamentos aleatórios normais inerentes à própria série de dados.

In the Pampas Region in the southwest of the State of Rio Grande do Sul, there are areas that show fragility in relation to soil and climatic characteristics. The sandy areas of this region have attracted special attention in the recent decades due to historical, socio economic and environmental issues. An increase in the amount of sand, or "sandization", occurred due to natural phenomena such as rainfall and wind. Therefore, the sandization process could be influenced by an increase of precipitation in the area. The goal of this work was to analyze precipitation during different time periods in Alegrete, Rio Grande do Sul, from 1928 to 2009 in order to identify evidence of changes in rainfall behavior. Rainfall data from the Brazilian National Water Agency (Portuguese acronym ANA) provided by the system hidroweb (http://hidroweb.ana.gov.br) were analyzed. After the data were organized on total monthly, trimestral and annual values, they were analyzed for their linear trend over time. The Mann-Kendall test was used to quantitatively evaluate positive and negative trends; however, the data did not provide evidence of climatic changes, but rather of normal random weather events during the time period studied.

Stalked barnacles Octolasmis lowei Darwin, 1851 are frequently found attached to decapod crustaceans. Their epibiotic association depends on many factors, which are mainly related to characteristics of the host's biology. This study evaluated the infestation and distribution of stalked barnacles in the branchial chambers of crabs, and analyzed the data with respect to the host's sex, maturity stage, molt cycle and size. The crab species Arenaeus cribrarius Lamarck, 1818, Callinectes danae Smith, 1869, Callinectes ornatus Ordway, 1863, Hepatus pudibundus Herbst, 1785, Libinia ferreirae Brito Capello, 1871, and Persephona punctata Linnaeus, 1758 were sampled and found to be infested by O. lowei. No juvenile crabs were infested. The prevalence of infestation by O. lowei was significantly different among C. danae, C. ornatus, and H. pudibundus males and females. All infested hosts were in the intermolt period. The mean size of infested crabs was larger than that observed for non-infested individuals. Internally, stalked barnacles were concentrated on the central gills or walls and floor of branchial chambers, suggesting that these gills provide more favorable conditions for the settlement and development of these epibionts. These results highlight the relationship between epibiont infestation and host biology, as well as the role of decapod crustaceans as a suitable substrate for the development of stalked barnacle O. lowei.

Existem muitas preocupações ecológicas do impacto que a construção de grandes lagos na Amazônia podem provocar, principalmente relacionadas ao microclima. Este estudo visa aumentar o conhecimento científico sobre a distribuição de chuvas antes e depois da formação do lago artificial da UHE Tucuruí-PA. Foram utilizados dados diários de precipitação dos períodos de 1972 a 1983 (pré-enchimento) e de 1984 a 1996 (pós-enchimento) para as cidades de Tucuruí e Marabá-PA. Comparando-se os totais mensais (pré e pós-enchimento), não se observam diferenças estatisticamente significantes (foram aplicados os testes de Fisher e Man-Whitney). Analisando-se a ocorrência de dias com precipitação superior a 5 e 25 mm.dia-1, também não se observam diferenças estatisticamente significativas. Há um leve aumento do número de dias com chuvas leves no final período sêco após a formação do lago, talvez devido a alta evaporação do lago artificial. Também não se observou modificações do início ou final da estação chuvosa.

There are a lot of ecological concern about the ecological impacts due to an artificial lake in Amazonia, especially related with the microclimate. This study aims to increase the scientific knowledge of the rainfall distribution prior and post flooding of the UHE Tucuruí-PA. Daily rainfall from 1972 until 1983 (prior inundation) and from 1984 until 1996 (post inundation) for Tucuruí and Marabá-PA. Comparing the monthly totals (prior and post), there is no statistical differences between the averages (using the statistical tests from Fisher and Man-Whitney). Analyzing the number of days with rainfall higher than 5 and 25 mm.day-1, there are also no statistical differences. It was observed a small increase of light rain during the end of the dry season. Also, the are no signal related to the modification of the onset or end from the rainy season.