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Oligochaeta assemblages are important components in freshwater environments, where their abundance and composition may indicate aspects related to water quality and sediment. The lack of information about these communities in Brazilian aquatic environments, as well as the application of native species as bioindicators of lotic environmental, stimulated the conception of this paper. Thus, the aim was to study the community of aquatic Oligochaeta in selected stretches of the Juruena River (MT), thereby generating grounds for future environmental monitoring action in lotic ecosystems. For this purpose, samples were analyzed at bimonthly intervals during the period from January to November 2009, in stretches of the Juruena River (Amazon River Basin) located in the State of Mato Grosso (MT). Two methods were used to collect the organisms: a) "D" network in small clusters of fixed macrophytes in the sediment on the river banks; and b) Ekman-Birge dredge in fine sediment. Preliminary results were 584 organisms distributed in 22 taxa. Of these, 22 valid species were identified. This number corresponds to approximately 25% of the aquatic oligochaete species registered in Brazil. Of these species, Limnodrilus hoffmeisteri, Dero nivea and Pristina rosea can be associated with organic enrichment conditions and/or some level of environmental degradation. Resumo: Comunidades de oligoquetos constituem importante componente em ambientes de água doce, onde sua abundância e composição podem indicar aspectos relacionados à qualidade da água e do sedimento. A carência de informações sobre estas comunidades em ambientes aquáticos brasileiros, bem como a aplicação de espécies nativas como bioindicadores de ambientes lóticos estimularam o desenvolvimento do presente trabalho. Assim, o objetivo foi estudar a comunidade de oligoquetos aquáticos em trechos selecionados do Rio Juruena (MT), gerando subsídios para futuras ações de monitoramento ambiental em ecossistemas lóticos. Métodos: Para isso foram analisadas amostras efetuadas em intervalos bimestrais durante o período de janeiro a novembro 2009, em trechos do Rio Juruena (Bacia Hidrográfica do Rio Amazonas) localizado no Estado de Mato Grosso (MT). Para coleta dos organismos foram utilizados dois métodos: a) rede em "D" em pequenos agrupamentos de macrófitas fixas no sedimento nas margens do rio; e b) draga Ekman-Birge em sedimento arenoso. Os resultados preliminares 584 organismos distribuídos em 22 táxons. Dentre estes, foram identificadas 22 espécies válidas. Esse número corresponde aproximadamente 25% das espécies de oligoquetos aquáticos registradas no Brasil. Destas espécies, Limnodrilus hoffmeisteri, Dero nivea e Pristina rosea podem ser associadas à condições de enriquecimento orgânico e/ou algum nível de degradação ambiental.

Cholinesterase (ChE) and ethoxyresorufin-O-deethylase (EROD) were of special interest to this study as these biochemical tools have been widely used for the determination of exposure to pollutants. In this study, the freshwater oligochaete Limnodrilus profundicola was tested for its potential as a bioindicator of freshwater pollution. For this purpose, the ChE and EROD activities of L. profundicola and the level of polycyclic aromatic hydrocarbons (PAH) of water samples collected from different sites along the Curuksu stream on the Menderes River (the ancient Meander) running through south-western Turkey were studied. First, these activities were characterized using, as model substrates, acetylthiocholine (ATC), propionylthiocholine (PTC), and butyrylthiocholine (BTC). Then, the in vivo effects of insecticides and pollutants on these activities were investigated. L. profundicola were exposed to various doses of methyl-parathion, methomyl, and deltamethrin. Although significant inhibition of ChE was detected with each of the insecticides, the highest level of inhibition was observed with methyl-parathion. In addition to the inhibition of ChE, the activity of EROD was induced by exposure to oil-contaminated sediments. Thus, although L. profundicola has a reputation for being very resistant to pollution (although it is not insensitive to it), we demonstrated that it may potentially be used as a bioindicator species for contaminant exposure when ChE and EROD are used as biomarkers. © 2010 Wiley Periodicals, Inc.