Chironomidae (Insecta, Diptera) associated with stones in a first-order Atlantic Forest stream

Abstract

Stones are stable substrates in streams, usually sheltering high richness and abundance of invertebrates. To investigate the structure of the Chironomidae assemblages associated with stones in a fi rst-order stream located in an Atlantic Forest reserve in two periods of the year, stones with diameters from 10 cm to 25 cm were collected along a stretch of 100 m in riffl e areas, during three months in the dry season and three months in the rainy season. The structure of the community was analyzed for each period through calculation of observed richness, Shannon's diversity (H'), and Pielou's evenness. The ordination of the samples from the dry and rainy seasons was evaluated by detrended correspondence analysis (DCA) and the presence of indicator species in the seasons was tested by IndVal analysis. The similarity in the faunistic composition between the periods was checked by ANOSIM. The results showed that, in general, the water velocity and rainfall were the abiotic variables that most strongly explained the abundance of larvae in the two periods studied, but the increase in these two parameters did not produce any signifi cant effect on the richness and abundance of the fauna, suggesting stability of the stones for the Chironomidae community. There was a signifi cant change in the faunistic composition (ANOSIM) and some samples had a stronger relationship with one of the seasons analyzed (DCA). The IndVal analysis indicated the characteristic taxa of each period, suggesting different responses to rainfall regimes. Besides this, Orthocladiinae were more abundant during the rainy season, while Chironomini was more abundant in the dry season. This study de monstrated the importance of the stones present in the stream channel as habitats for Chironomidae fauna, mainly in periods of high rainfall and water fl ow.Key words: aquatic insects, lotic systems, rainfall variation, substrates. RESUMENLas piedras forman un sustrato estable en los arroyos, albergan usualmente alta riqueza y abundancia de invertebrados. Se evaluó la estructura de la fauna de Chironomidae asociada a las piedras de un arroyo de primer orden ubicado en una reserva de Mata Atlántica. Para ello se recolectaron 180 piedras de 10 cm a 25 cm de diámetro a lo largo de un trecho de 100 m en área de corredera, durante tres meses del periodo seco y tres meses del periodo lluvioso. La estructura de la comunidad fue analizada para cada periodo a través del cálculo de riqueza taxonómica observada, diversidad de Shannon (H') y la equidad de Pielou (E), al respecto. La ordenación de las muestras de las estaciones seca y lluviosa fue evaluada por análisis de correspondencias sin tendencia (DCA) y la presencia de especies indicadoras de los períodos se ensayó por análisis IndVal. La similitud en la composición de la fauna entre los períodos se comprobó mediante el análisis de ANOSIM. Los resultados muestran que en general la disminución del fl ujo y la precipitación fueron las variables abióticas que más explicaron la abundancia de larvas en los dos pe...

First record of Lopescladius Oliveira, 1967 (Chironomidae: Orthocladiinae) in the Piranhas-Açu River basin, Brazil, with ecological notes on its habitat use

“…This is aggravated by the fact that aquatic larvae of this taxon are small and can be overlooked during sorting or not collected by standard methods (Farias et al in press). Therefore, the presence of this genus in highly variable Janeiro, São Paulo, Paraná, Santa Catarina and Rio Grande do Sul) Henriques-Oliveira et al 2003;Roque 2005;Anselmini 2007;Resende and Taketa 2007;Corbi and Trivinho-Strixino 2008;Sanseverino and Nessimian 2008;Lara 2011;Lisboa et al 2011;Rosa et al 2011;Sensolo et al 2012;Rosa et al 2013;Salvarrey et al 2014;Saulino et al 2014) and a few of the central and northern states (such as Mato Grosso do Sul, Amazonas and Pará) (Hagenlund et al 2010;Rosin et al 2010;Mendes and Pinho 2014). In the northeastern Brazil, this genus has been reported in the states of Alagoas and Piaui (Freitas 2004;Soares et al 2013).…”