Chironomidae and Oligochaeta for water quality evaluation in an urban river in southeastern Brazil.

Considering the importance of benthic macroinvertebrates for diagnosis of variations in the ecological conditions of aquatic habitats, the aim of this study was to investigate the structure of the Chironomidae and Oligochaeta assemblages along an organic pollution gradient. The fauna specimens were obtained with the use of artificial substrates, and the environmental variables were recorded at five sites of the São Lourenço River, during 12 months. Metrics of the assemblage and detrended correspondence analysis were used to verify the response of the fauna to the pollution gradient. Procrustes analysis was used to verify whether the data on the Chironomidae and Oligochaeta assemblages, as well as the taxonomic and numerical resolution of these groups, provide similar results in relation to the pollution gradient. The richness, evenness, and taxonomic composition of the Chironomidae and Oligochaeta assemblages varied significantly among the collection sites, with distinct conservation conditions. Genera of the subfamilies Orthocladiinae and Tanypodinae were associated with the sites upstream of the urban area, where the dissolved oxygen levels are higher. Species of Oligochaeta and the genus Chironomus were associated with more organically polluted sites. No concordance was observed in the response of the Chironomidae and Oligochaeta assemblages in relation to the environmental variables, indicating the need to use both groups in biomonitoring studies. On the other hand, both the data on composition (presence or absence) and those on the lowest taxonomic resolution (abundance of subfamilies) were effective to diagnose the pollution gradient in the river studied. Therefore, when the environmental conditions along a river's gradient are contrasting, we suggest the use of the lowest taxonomic resolution of Chironomidae and Oligochaeta in biomonitoring. That procedure considerably reduces the assessment time, besides being a method that can be used by people not specializing in the taxonomy of groups.

Aquatic oligochaetes associated with bryophytes in an Atlantic Forest stream

There are few reports in the literature about the colonization of benthic macroinvertebrates on bryophytes. The aim of the present study was to analyzed the oligochaetes established on bryophytes adhered to stones in a first-order stream. The collections were carried out in an Atlantic Forest fragment area during the dry and rainy seasons. We identified 15 taxa from a total of 422 oligochaetes specimens, of which the most abundant were Pristina sp.1, Enchytraeidae and Pristina jenkinae. Unlike other habitats, where the abundance of macroinvertebrates tends to be greater in the dry season, we did not find any significant differences in the abundance, richness, composition and diversity between the two periods. The results of this study indicate that bryophytes are possible areas of refuge for oligochaetes in periods of faster water flow.

Existem poucos registros na literatura sobre a colonização de macroinvertebrados bentônicos em briófitas. O presente estudo teve como objetivo analisar a fauna de oligoquetas em briófitas aderidas a pedras em um córrego de primeira ordem. As coletas foram realizadas em um fragmento de Mata Atlântica durante os períodos seco e chuvoso. Foram identificados 15 taxa de um total de 422 espécimes de oligoquetas, sendo os mais abundantes Pristina sp.1, Enchytraeidae e Pristina jenkinae. Ao contrário de outros habitats, onde a abundância de macroinvertebrados tende a ser maior no período de estiagem, diferenças significativas na abundância, riqueza, composição e diversidade não foram observadas em relação aos dois períodos. Os resultados do presente estudo indicam que as briófitas são possíveis áreas de refúgio para os oligoquetas em período de maior corrente.

Inventory and distribution of Oligochaeta (Annelida, Clitellata) in first-order streams in preserved areas of the state of Minas Gerais, Brazil / Inventário e distribuição de Oligochaeta (Annelida, Clitellata) em córregos de primeira ordem localizados em áreas preservadas do estado de Minas Gerais, Brasil

Data resulting from species inventories shed light on the richness and distribution of various groups. In Minas Gerais, work on inventory and distribution of the oligochaetes of lotic environments in preserved areas are non-existent. Therefore, this study aimed to inventory the limnic oligochaetes fauna of first-order streams located in four preserved areas, to expand knowledge of the ecology and distribution of this group. In total, 19 taxa were inventoried, belonging to the families Naididae and Enchytraeidae and the superorder Megadrili (earthworms), with the genus Pristina having the largest number of species. The number of species found in this investigation corresponds to 22% of oligochaetes species recorded in Brazilian aquatic environments. The results obtained add important knowledge of the distribution of some oligochaetes species in Brazil, represent the first records of species for the four preserved areas studied and confirm the first occurrence of various species in the state.

Os dados resultantes de um levantamento fornecem informações sobre a riqueza e distribuição de diversos grupos. Em Minas Gerais, trabalhos sobre inventário e distribuição de oligoquetas de ambientes lóticos em áreas preservadas são inexistentes. Dessa forma, este estudo objetivou inventariar a fauna de oligoquetas límnicos de córregos de primeira ordem localizados em quatro áreas preservadas, visando ampliar as informações sobre ecologia e distribuição deste grupo. Foram inventariados 19 taxa pertencentes às famílias Naididae, Enchytraeidae e à superordem Megadrili, sendo o gênero Pristina o de maior número de espécies. O número de espécies encontradas neste trabalho corresponde a 22% das espécies de oligoquetas registrados em ambientes aquáticos brasileiros. Os resultados obtidos ampliam o conhecimento sobre a distribuição de algumas espécies de oligoquetas no Brasil, representam os primeiros registros de espécies para as quatro áreas preservadas estudadas e confirmam a primeira ocorrência de várias espécies no Estado.