Variation of the ichthyofauna along the Goioerê River: an important tributary of the Piquiri-Paraná basin

The construction of reservoirs is considered an important source of impacts on the fish fauna, severely altering the structure of the assemblage. This paper aimed to describe the structure of the fish assemblage of the Goioerê River, determining its longitudinal distribution and patterns of species dominance. The evaluation of its longitudinal variation in the diversity and abundance of the fish assemblage was conducted in July and October 2004 and January and May 2005. The collections were carried out near the headwaters (Gurucaia), middle stretch (Olaria), just above the falls (Paiquerê) and downstream (Foz). Forty-four species were captured. The Gurucaia fish assemblages differed significantly from Olaria, Paiquerê and Foz. The Olaria assemblages differed significantly from the Foz. Gurucaia showed the lowest diversity and abundance of species. Astyanax aff paranae Eigenmann,1914 (78% of the total) was found to be dominant at this site. Almost the same species richness was found at Olaria and Paiquerê, although Olaria had the greatest abundance of individuals. Astyanax aff paranae, Cyphocharax modestus (Fernández-Yépez, 1948) and Astyanax altiparanae Garutti & Britski, 2000 were the top three dominants and comprised over 71% of the total number of fish caught. At Paiquerê, Astyanax altiparanae, Hypostomus aff ancistroides (Ihering, 1911) and Loricariichthys platymetopon Isbrücker & Nijssen, 1979 composed 58% of the catches. Thirty-one species were recorded at Foz, which presented the greatest richness. The most abundant species were Apareiodon affinis (Steindachner, 1879), Galeocharax knerii (Steindachner, 1879) and A.altiparanae, which contributed to 50% of the total catches in this environment.These results record the fish biodiversity and how the community is longitudinally structured in the Goioerê River, and also demonstrate how this type of evaluation is important to understanding the fish community patterns and finding solutions to problems related to the conservation and management of the basin.

Ecomorphology and diet reflect the spatial segregation between two Siluriformes species inhabiting a stream of the Bodoquena Plateau, in Central Brazil

Pimelodella taenioptera Miranda Ribeiro, 1914 and Imparfinis schubarti (Gomes, 1956) are two of the most common fish species in Bodoquena Plateau streams, Paraguay basin. These species have benthic habits and subaquatical observations suggested that they present differentiation in their preference for mesohabitat types. Pimelodella taenioptera shows preference for slow waters, such as pools, while I. schubarti is associated to riffles. In this study we investigated if the known patterns of mesohabitat use of P. taenioptera and I. schubarti can be predict by their ecomorphological and trophic traits. We described the dietary habits and ecomorphological attributes of P. taenioptera and I. schubarti individuals, captured in the Parque Nacional da Serra da Bodoquena (PNSB), Mato Grosso do Sul state, central Brazil. Pimelodella taenioptera presented a more generalist diet, consuming a total of 23 different food items. Imparfinis schubarti have a diet based exclusively on aquatic insects. The ecomorphological analysis revealed that the species differed in relation to five morphological traits associated to habitat use (p <0.01). The results of this study reveal a clear functional dissimilarity between P. taenioptera and I. shubarti. The observed trophic and ecomorphological patterns are congruent with the known habitat use for these species and probably reflect the spatial and temporal variability on conditions and resources present in riffles and pools. Therefore, as expected, the morphological and feeding attributes represent predictive information related to mesohabitat use.

Biologia reprodutiva de Macrobrachium jelskii (Crustacea, Decapoda, Palaemonidae) no Rio São Francisco, Minas Gerais, Brasil

RESUMO O objetivo foi avaliar a biologia reprodutiva do camarão- sossego Macrobrachium jelskii (Miers, 1877) no Rio São Francisco, com ênfase na razão sexual, período reprodutivo, maturidade sexual e fecundidade. As coletas foram realizadas mensalmente entre março de 2005 e fevereiro de 2006 exceto nos meses de abril e outubro, nos dois pontos de coleta do Rio São Francisco, Represa de Três Marias (Estação Ecológica de Pirapitinga), a montante da barragem da usina hidroelétrica de Três Marias e a jusante da barragem, localizados no município de Três Marias, região central de Minas Gerais, Brasil. O puçá de 1 m² de boca e malha de 1,42 mm foi passado sob a vegetação marginal e na água à margem dos dois pontos de coleta, por um coletor em um período de até 30 minutos. Em laboratório, os espécimes foram identificados, mensurados e sexados. Um total de 2.945 espécimes foi analisado a montante, no qual correspondem a 1.064 machos e 1.857 fêmeas (1.653 não ovígeras e 204 ovígeras) e 1.973 a jusante, onde 1.120 machos e 841 fêmeas (643 não ovígeras e 198 ovígeras). A razão sexual diferiu significativamente a favor de fêmeas de M. jelskii a montante (0,57; χ2= 215,28; p < 0.01) e a favor dos machos a jusante (1,33; χ2= 39,69; p < 0.01). Ambas as populações possuem um período reprodutivo contínuo-sazonal com pico em janeiro e novembro para os camarões a montante e a jusante, respectivamente. A fecundidade média de M. jelskii foi de 37 ± 14 ovos (5 a 78 ovos) a montante da barragem e de 35 ± 14 ovos (5 a 69 ovos) a jusante. A razão sexual desviada para os machos de M. jelskii à jusante sugere que as fêmeas apresentaram o comportamento de se abrigarem entre as vegetações marginais. A razão sexual desviada para as fêmeas a montante demonstra a real proporção de machos e fêmeas, que pode ser considerada para a espécie no Rio São Francisco. O tamanho dos ovos carregados pelas fêmeas a jusante foi influenciado pelas baixas temperaturas da água proveniente da represa.

Chagas' disease in the Amazon Basin: V. Periurban palms as habitats of Rhodnius robustus and Rhodnius pictipes - triatomine vectors of Chagas' disease

Trypanosoma cruzi infected Rhodnius robustus and/or Rhodnius pictipes were commonly found, in large numbers, in the Brazilian Amazonian palms Maximiliana regia ("inajá"), Acrocomia sclerocarpa ("mucajá") and Orbignya speciosa ("babaçu"). The common opossum, Didelphis marsupialis, was the animal most frequently associated with triatomine infested palms. R. pictipes, frequently light-attracted into houses from palm trees, was the probable source of an acute case of Chagas' disease in the vicinity of Belém. It is considered that triatomine infested palms are likely to cause some cases of acute Chagas' disease in the States of Amazonas and Rondônia. Possible control methods are suggested.

A rewiew of the subgenus Trichopygomyia Barretto, 1962; with description of a new species from the brazilian Amazon Basin (Diptera: Psychodidae, Phlebotominae)

The subgenus Trichopygomyia Barreto, 1962 of the phlebotomine genus Lutzomyia França, 1924 is reviewed. This subgenus corresponds to the informal species group longispina of Theodor (1965). Lutzomyia (Trichopygomya) ratcliffei n.sp. from the Brazilian Amazon Basin is described. Figures, keys, distribution maps and notes on ecology are presented for all the known forms. The better known species are most frequently encountered in armadillo burrows and, therefore, could well be vectors of Leishmania.

A new sand fly in the subgenus Nyssomyia (Diptera, psychodidae) from the Amazon basin of Brazil

Lutzomyia (Nyssomyia) waltoni m.sp., uma nova espécie de flebótomo é descrita e ilustrada. Observações ecológicas disponíveis são apresentadas. (AU)

Leishmania infections in Lutzomyia longipalpis (Diptera: Psychodidae) on the Island of Sao Luis, Maranhao State, Brazil

Dissection of Lutzomyia longipalpis, captured in the São Luis focus of visceral Leishmaniasis revealed a 1.8% promastigote infection rate.

Effects of immigration on the prevalence of malaria in rural areas of the Amazon basin of Brazil

Epidemiological studies were conducted on malaria in three rural areas of the Amazon basin in the State of Rondônia: the town of Costa Marques, Forte Príncipe da Beira (Fort), and an immigrant settlement in the nearby forest. These studies were instituted to document the malaria problem and to describe the role of immigration on its distribution and prevalence. Hospital records in the town show that the number of malaria cases increased five fold from 1983 to 1987 and that the predominant malaria parasite changel from Plasmodium vivax to P. falciparum. Increased malaria followed increased immigration and colonization of the forest. A series of epidemiologic studies suggested the linkage between malaria and immigration as the prevalence of malaria was 1-2% at the Fort, a stable community, 8-9% at Costa Marques, a growing community, and 14-26% in the new settlements in the forest.

Ecological aspects of nematode parasites of introduced salmonids from Valdivia river basin, Chile

Between 1986 and 1987 fishes distributed among the following species introduced in Chile, and from different sectors of the Valdivia river basin (39º30' - 40º00', 73º30' - 71º45'W), were examined: 348 Salmo trutta, 242 Salmo gairdneri, 24 Cyprinus carpio and 52 Gambusia affinis holbrooki. The presence of Camallanus corderoi and Contracaecum sp. in S. gairdneri and of C. corderoi in S. trutta is recorded in Chile for the first time. Cyprinus carpio and G. a. holbrooki did not present infections by nematodes. The prevalence and mean intensity of the infections by nematodes presented significant differences among some sectors of the Valdivia river basin. In general, the prevalence and intensity of the infections by C. corderoi were greater than those by Contracaecum sp. The infections in S. gairdneri were higher than in S. trutta. The sex of the hosts had no influence on the prevalence and intensity of the infections by both nematodes. The length of the hosts did have an influence, except in the case of the infections by Contracaecum sp. in S, gairdneri. The infrapopulations of both nematode species showed over dispersion in most cases. The diet of the examined salmonids suggests that they would become infected principally throught the consuption of autochthonous fishes.

Vector incrimination and effects of antimalarial drugs on malaria transmission and control in the Amazon Basin of Brazil

World ecosystems differ significantly and a multidisciplinary malaria control approach must be adjusted to meet these requirements. These include a comprehensive understanding of the malaria vectors, their behavior, seasonal distribution and abundance, susceptibility to insecticides (physiological and behavioral), methods to reduce the numbers of human gametocyte carriers through effective health care systems and antimalarial drug treatment, urban malaria transmission versus rural or forest malaria transmission, and the impact of vaccine development. Many malaria vectors are members of species complexes and individual relationship to malaria transmission, seasonal distribution, bitting behavior, etc. is poorly understood. Additionaly, malaria patients are not examined for circulating gametocytes and both falciparum and vivax malaria patients may be highly infective to mosquitoes after treatment with currently used antimalarial drugs. Studies on the physiological and behavioral effects of DDT and other insecticides are inconclusive and need to be evalusted.

Seroprevalence of viral hepatitis in riverine communities from the Western Region of the Brazilian Amazon Basin

The western region of the Brazilian Amazon Basin has long been shown to be a highly endemic area for hepatitis B and hepatitis D viruses. Data concerning the prevalence of hepatitis C and E viruses in this region are still scarce. In this study we investigated the presence of hepatitis A, B, C, D and E viruses infection in communities that live along the Purus and Acre rivers in the states of Acre and Amazonas within the Amazon Basin. A total of 349 blood samples were collected and tested for hepatitis A-E serological markers (antibodies and/or antigens) using commercial enzyme linked immunosorbent assays. Anti-HCV positive sera were further assayed by an immunoblot. HBsAg positive sera were subtyped by immunodifusion. The overall prevalence for hepatitis A, B, C, and E were 93.7%, 66.1%, 1.7%, and 4%, respectively. A very high prevalence of delta hepatitis (66.6%) was found among HBsAg positive subjects. Hepatitis A, B and D viruses were shown to be largely disseminated in this population, while hepatitis C and E viruses infection presented low prevalence rates in this region. The analysis of risk factors for HBV infection demonstrated that transmission was closely associated with sexual activity.