In the agricultural cultivation, the Pyrimethanil (4,6-dimethyl-N-phenyl-2-pyrimidinamine) fungicide is one of the most widely used compound in monocultures and has been detected in aquatic ecosystems. These genotoxic products increase the frequency of lesions in the DNA molecule, thereby increasing the risk of replication and transcription of altered DNA sequences. This study aimed to assess the loss of genetic diversity of Chironomus sancticaroli, a Brazilian native insect species, exposed to Pyrimethanil fungicide, using RAPD-PCR (random amplified polymorphic DNA) technique. The results showed that there was significant loss in the genetic diversity in the organisms exposed to high Pyrimethanil concentrations when compared with control site. Our findings reveal that RAPD-PCR is an effective method to access genetic loss derived to fungicide use and that the agriculture application may lead to a decrease in aquatic biota genetic diversity. This finding has important implications for conservation strategies and ecological management environments.

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.

, representing 28% of total dissolved neutral carbohydrates (TDnC) on average. Rhamnose concentration was linearly correlated with TDnC concentration and with the abundance of Microcystis aeruginosa, which releases a rhamnose-rich extracellular polysaccharide (EPS). This correlation was slightly stronger when the cell densities of Aulacoseira granulata, Cryptomonas tetrapyrenoidosa and Anabaena spiroides, also rhamnose-rich EPS producers, were included. The enzymatic activity on methylumbelliferyl (MUF)-α-L-rhamnopyranoside (EARh) ranged from 0 to 57.8 nmol MUF l −1 h −1. Glucose concentrations were found to vary from 0 to 4.15 µmol l −1 (27.5% of TDnC), and the enzymatic activity on MUF-β-D-glucopyranoside (EAGl) ranged from 7.4 to 116.9 nmol MUF l −1 h −1. Variation of EARh in time was directly correlated with the density of M. aeruginosa, and with rhamnose concentration in TDnC, while EAGl activity was correlated with density of M. aeruginosa only for variation with depth. Analysis of rhamnose, glucose, TDnC, EARh, EAGl, and bacterial density at each depth individually provided evidence that EPS released was employed as bacterial substrates, despite the permanent presence of TDnC from surface to bottom, owing to its constant production. These results also showed strong evidence that both enzymes were induced by EPS. Our results strongly suggest that the predominant phytoplankton species, known producers of rhamnose and glucose-rich EPS, α-Lrhamnosidase(s) activity and rhamnose concentration in the Barra Bonita Reservoir were coupled.

Dissolved carbohydrates and abundant algae of Barra Bonita Reservoir were studied monthly from June 2002 to January 2004 in six depths whose values vary depending on the seasons and the water level at a sampling site located 3 km upstream the Reservoir dam. Nearly 90% of the dissolved carbohydrates were constituted of polymeric hydrolysable carbohydrates (polysaccharides or oligosaccharides). Analysis of variance detected variability among concentrations of dissolved carbohydrates only in temporal scale (p < 0.05), whereas in vertical axis the concentrations of these sugars were uniform (p > 0.05). The monosaccharide composition of the sugars found in the reservoir was galactose, rhamnose, glucose e fucose. During the sampling period, higher concentrations of dissolved carbohydrates, mostly polymeric, occurred together with large phytoplanktonic blooms, predominantly cyanobacteria, which probably were the main source of extracellular polysaccharides in the system. O estudo dos carboidratos dissolvidos e sua relação com as algas abundantes no reservatório de Barra Bonita, foi realizado em coletas mensais (junho de 2002 a janeiro de 2004), em seis profundidades na coluna d'água, cujos valores variaram dependendo da estação do ano e do nível do reservatório, num ponto fixo, localizado 3 km a montante da barragem. Aproximadamente 90% dos carboidratos dissolvidos neste reservatório foram constituídos por carboidratos poliméricos hidrolisáveis (polissacarídeos ou oligossacarídeos). A análise de variância detectou variabilidade entre as concentrações dos carboidratos dissolvidos apenas em escala temporal (p < 0,05), sendo que no eixo vertical, as concentrações destes açúcares apresentaram-se homogêneas (p > 0,05). A composição monossacarídica dos açúcares encontrados no reservatório foi galactose, ramnose, glicose e fucose. Na maioria dos meses amostrados, as concentrações de carboidratos dissolvidos, a maioria deles poliméricos, ocorreram concomitantemente ao registro de florescimentos das espécies abundantes, principalmente cianofíceas, que provavelmente foram as principais fontes de polissacarídeos extracelulares para o sistema.Palavras-chave: fitoplâncton, reservatório eutrófico, polissacarídeos extracelulares.

The aquatic environment is a dynamic product of complex interactions among biotic and abiotic factors. Alterations in their chemical and physical characteristics may directly affect their biological activities, compromising ecosystem functioning and the provisioning of ecosystem services that depend on biodiversity. In the last five decades, agriculture expansion and agrochemical utilization have increased following food demand. The trend is anticipated to continue due to factors like population growth, the emergence of new pests, and the use of biofuels. The increasing application of agrochemicals is an emerging threat to aquatic ecosystems due to their constant entry into water bodies and their high toxicity. Here, we present a brief synthesis of the effects of agrochemicals in freshwater systems, mainly their impacts on an important biological component of aquatic biota, the macroinvertebrates. We also present some key points about the use of different endpoints, such as biologic interactions and genetic diversity loss, in ecotoxicological analyses and determination of new test organisms to be explored and standardized for tropical regions.