La taxonomía de Chironomidae se apoya fuertemente en la integración de las características morfológicas de todas las fases del ciclo de vida, las cuales se pueden obtener mediante la cría en laboratorio. Este estudio desarrolló un método de cría en laboratorio de larvas de Chironomidae de ambientes lóticos. El método consta de una circulación constante de agua y distintos ítems alimenticios. Esta metodología ha permitido obtener asociaciones de los estados de larva, pupa y adulto para la identificación de especies presentes en una región de Argentina en la que el estado de conocimiento de la familia Chironomidae es incipiente.

The taxonomy of Chironomidae is strongly supported by the integration of morphological characteristics of all stages of the life cycle, which can be obtained through laboratory rearing. This study was developed in laboratory to test rearing method for lotic Chironomidae larvae. The method included constant water circulation and different food items. This methodology allowed obtaining associations of larva, pupa and adult stages for the identification of species from an Argentinean region in which the knowledge of Chironomidae family is incipient.

OBJETIVOS: Os objetivos deste estudo são avaliar os efeitos da variabilidade espacial e temporal sobre a fauna de macroinvertebrados em deriva e no substrato de um riacho de montanha. MÉTODOS: A área de estudo situa-se no riacho Achiras (região Central da Argentina). Este riacho é endorréico e suas fontes estão localizados no extremo sul das serras de Comechingones. Foram coletadas três amostras de bentos com a rede de Surber de 300 µm e 0.09 m². Em deriva, foram coletadas três amostras com redes de 1 m long, 300 µm e 0.0192 m². A identificação taxonômica dos organismos foi feita até o menor nível taxonômico possível. A fim de caracterizar a fauna em deriva e a fauna associada ao fundo foram estimadas a abundância total, a riqueza taxonômica e os índices de equitabilidade e Shannon e eles foram testados com uma forma de análise de variância (ANOVA). A fim de avaliar os padrões de distribuição de deriva e amostras de bentos, foi realizada análise de correspondência canônica (CCA). RESULTADOS: Um total de 61 táxons foram identificados na deriva e 82 nos bentos. Observamos semelhança taxonómica de 26.3% dentre os dois conjuntos, de acordo com o índice de Jaccard. Na deriva e bentos, os artrópodes apresentaram a maior abundância. Insecta contribuiu com o maior número de táxons. As ordens mais abundantes foram Ephemeroptera, Trichoptera e Diptera. Anacroneuria sp. (Perlidae) e Podonominae (Chironomidae) foram registrados pela primeira vez para a comunidade bentônica do riacho Achiras. CONCLUSÃO: Neste estudo, constatamos que a organização estrutural da deriva e da comunidade de macroinvertebrados bentônicos exibiu diferentes padrões de variação em escalas espaciais e temporais.

AIMS: The aims of this study are to evaluate the effects of spatial and temporal variability of the macroinvertebrate fauna in drift and in the substrate of a mountain stream. METHODS: The study site is located in Achiras stream (Central, Argentina). This is an endorheic fluvial course whose headwaters are located in the southern extreme of Los Comechingones Mountains. Three replicate Surber samples were collected from benthos with 300 µm, 0.09 m² nets. Three drifting fauna samples were collected using drift nets, 1 m long, 300 µm and 0.0192 m². The taxonomic identification of specimens was performed according to the lowest possible taxonomic level. In order to characterize the drifting and benthic fauna, total abundance, taxonomic richness, Shannon and evenness indices were estimated and they were tested with two-way analysis of variance (ANOVA). In order to assess the distribution patterns of drift and benthos samples, we performed Canonical Correspondence Analysis (CCA). RESULTS: A total of 61 taxa were identified in drift and 82 in benthos. A 26.3% taxonomic similarity between the two assemblages was observed, according to the Jaccard index. In drift and benthos, Arthropoda presented higher abundance and Insecta contributed with more taxa and it was also the most abundant. The most abundant orders were Ephemeroptera, Trichoptera and Diptera. In the present study, Anacroneuria sp. (Perlidae) and Podonominae (Chironomidae) were first recorded for benthic community of Achiras stream. CONCLUSION: In this study we found that the structural organization of the drifting and benthic macroinvertebrate community shows different patterns of variation at spatial and temporal scales.

Regulation of rivers and streams modifies parameters that directly influence on the biota. In Achiras-del Gato endorheic basin has completed the construction of a midsize dam that will alter the limnological characteristics of the system and the structure of benthic communities. This study provides the first taxonomic records of macrobenthos of this lotic system and analyzes the spatial and temporal variations of the community structure in the foothills stretches of Achiras stream. Zoobenthos samples were collected and abiotic variables were recorded in runs and riffles, during a year, in two sites located upstream and downstream of the dam area, prior to the dam was built. For each site, habitat and season we determined the abundance, frequency, taxonomic richness, Shannon and evenness, and the data were analyzed using one-way and three-way ANOVA. Attributes of the reference communities were complemented by the determination of ecological indicators and detectors, and exclusive taxa. In the first site 73 taxa were recorded, Simulium was the most abundant and Leptohyphes eximius Eaton, 1882, was the most frequent. In the second site we found 75 taxa, Caenis was the most abundant and Cricotopus sp. 3, was the most frequent. In this study composition and distribution of the biota and indicators taxa are discussed. We determined that the community attributes were affected by the hydrological periods in wich the samples were taken. Achiras stream has a phreatic-pluvial hydrological regime with low flows in winter and high flows in summer. Therefore, we expect changes in native biota and in system integrity in response to hydraulic variability reduction when Achiras dam start functioning and alters the natural flow.

La regulación de ríos y arroyos mediante diques modifica parámetros que influyen directamente sobre la biota. En la cuenca endorreica Achiras-del Gato ha finalizado recientemente la construcción de una presa de mediana envergadura que alterará las características limnológicas del sistema y la estructura de las comunidades bentónicas. Este estudio aporta los primeros registros del macrobentos de este sistema lótico y analiza la variación espacio-temporal de la estructura de la comunidad en tramos pedemontanos del arroyo Achiras. Durante un año, antes de la construcción de la presa, se colectaron muestras de zoobentos y se registraron variables abióticas en correderas y rabiones de dos sitios del arroyo, uno situado río arriba del área del dique y otro aguas abajo de la misma. Para cada sitio, hábitat y estación del año se determinó abundancia, frecuencia, riqueza taxonómica, Índice de Shannon y equidad, y se analizaron mediante ANOVA de una y tres vías. Los atributos de las comunidades de referencia se complementaron con la determinación de taxa exclusivos e indicadores y detectores ecológicos. En el primer sitio se registraron 73 taxa, Simulium fue más abundante y Leptohyphes eximius Eaton, 1882, más frecuente. En el segundo se hallaron 75 taxa, Caenis fue más abundante y Cricotopus sp. 3 más frecuente. La abundancia y la riqueza fueron significativamente mayores en primavera, y la diversidad en rabiones de invierno. Se determinó que los atributos de la comunidad estuvieron afectados por la época de muestreo. El arroyo Achiras posee un régimen hídrico freático-pluvial, con caudales bajos en invierno y altos en verano, por lo que se esperan cambios en la biota nativa y la integridad del sistema en respuesta a la reducción de la variabilidad hidráulica cuando el funcionamiento de la presa altere el caudal natural.