Abstract Studies of the relationships between the temporal variation of biological phenomena and environmental factors are essential to understanding the dynamics of communities. Phenology is a structuring element and, together with voltinism, is related to timing of reproductive activities. The aim of this study is to ascertain the structure and composition of the Chironomid assemblage and its emergence patterns in relation to the environmental variables through the use of the Chironomid pupal exuviae technique using the Neotropical streams as a model. The streams presented similar species compositions. The highest density of pupal exuviae was recorded during spring and the greatest richness in late summer and early autumn. Chironominae presented greater prevalence throughout the year with oscillations for Orthocladiinae and Tanypodinae. Chironominae and Tanypodinae presented emergence peaks in spring-summer and Orthocladiinae in autumn-winter. Rainfall, photoperiod and water and air temperatures structured the Chironomid assemblage, influencing emergence. Univoltine, bivoltine and multivoltine species were recorded. The species presented interspecific synchronization in emergence peaks at different times of the year.

The first records from Argentina of larvae of Goeldichironomus petiolicola Trivinho-Strixino & Strixino mining in Eichhornia crassipes (Martius) Solms petioles in wetlands of the Paraná River floodplain were analyzed. G petiolicola larvae and pupae were collected seasonally during 2005 from stands of E. crassipes and bottom sediment samples in floodplain habitats. Larvae inside E. crassipes petioles were reared with the purpose of obtaining their complete life cycle. G. petiolicola was the most abundant chironomid species living inside E. crassipes petioles; the III and IV instar larvae and pupae were found during all the seasons while the I and II instar larvae were not found. The highest average densities of G. petiolicola larvae inside the E. crassipes petioles were recorded in Autumn-Winter (588.5 ind.kg-1 dw - 778.7 ind.kg-1 dw). This suggests that they have better conditions for survival, allowing the individuals to develop more slowly until the next flooded period with higher temperatures. The r (Dyar) value obtained was 1.66. We conclude that G. petiolicola mines into E. crassipes petioles mainly when the plants begin their senescence process and does not cause important damage to them.

Se presenta el primer registro para Argentina de Goeldichironomus petiolicola Trivinho-Strixino & Strixino, especie cuyos estadios inmaduros minan dentro de los pecíolos de Eichhornia crassipes (Martius) Solms, en humedales del río Paraná Medio. Las larvas y pupas de G petiolicola fueron recolectadas estacionalmente durante 2005, de los stands de E. crassipes y en muestras de sedimento en diferentes ambientes de la llanura. Ejemplares de la especie fueron criados en laboratorio a fin de completar su ciclo de vida. G petiolicola fue el quironómido más abundante que habita en el interior de los pecíolos de E. crassipes, se registraron los estadios de larva III y IV y pupa durante todas las estaciones. No fueron registrados los estadios larvales I y II. Las mayores densidades medias de G petiolicola fueron obtenidas en otoño-invierno (588,5 ind.kg¹ dw - 778,7 ind.kg¹ dw), esto sugiere que presentan mejores condiciones para la supervivencia, lo que permite a los individuos obtener un desarrollo más lento hasta el próximo período de inundación, con mayores temperaturas. El valor calculado de r (Dyar) fue 1,66. G petiolicola mina dentro de los pecíolos de E. crassipes, principalmente, durante el inicio del proceso de senescencia del vegetal, por lo que no provoca daños importantes.

Las larvas de quironómidos son componentes importantes de la biota acuática por su participación en las tramas tróficas y por ser bioindicadores de condiciones ambientales. Muchos estudios de laboratorio han analizado los efectos de diferentes contaminantes sobre quironómidos, especialmente sobre Chironomus calligraphus Goeldi, 1905. Sin embargo, poco se conoce sobre los atributos de su ciclo de vida. El objetivo de este estudio fue analizar el ciclo de vida de C. calligraphus en condiciones de laboratorio. La razón de crecimiento entre estadios larvales fue aproximadamente constante (r= 1,60 ±0,02), el tiempo de desarrollo (D) fue 15 días y el tiempo mínimo de generación (G) fue 18 días. De acuerdo a estos resultados y a observaciones realizadas en campo, C. calligraphus es una especie con ciclo de vida temperatura-dependiente con generaciones superpuestas de corta duración en primavera-verano y con una o dos generaciones de mayor duración en invierno.

Chironomid larvae are important components of aquatic biota, due to their abundance and participation in food webs, and because they are considered environmental bioindicators. Many laboratory studies have analyzed the effects of pollutants on chironomids, especially on Chironomus calligraphus Goeldi, 1905. However, little is known about the life cycle attributes of Chironomidae (Diptera). The main pourpose of this study was to analyze C. calligraphus life cycle under laboratory conditions. The growth rate was almost constant between larval instars (r= 1.60 ±0.02), the immature development time (D) was 15 days and the minimum generation time (G) was 18 days. According to these results and field observations C. calligraphus has a temperature-dependent life cycle, with several overlapped short duration cohorts in spring-summer followed by one or two generations of longer duration in winter.

As larvas de quironomídeos são componentes importantes da biota aquática por sua participação nas tramas tróficas e por serem bioindicadores de condições ambientais. Muitos estudos de laboratório têm analisado os efeitos de diferentes contaminantes sobre quironomídeos, especialmente sobre Chironomus calligraphus Goeldi, 1905. No entanto, pouco se conhece sobre os atributos de seu ciclo de vida. O objetivo deste estudo foi analisar o ciclo de vida de C. calligraphus em condições de laboratório. A razão de crescimento entre estágios larvais foi aproximadamente constante (r= 1,60 ±0,02), o tempo de desenvolvimento (D) foi de 15 dias e o tempo mínimo de geração (G) foi de 18 dias. De acordo a estes resultados e a observações realizadas em campo, C. calligraphus é uma espécie com ciclo de vida temperatura-dependente com gerações superpostas de curta duração em primavera-verão e com uma ou duas gerações de maior duração no inverno.