ABSTRACT
This study aimed to examine spatiotemporal variations in chironomid assemblages and to detect how environmental variables affect their structure. We sampled seven streams at low and high altitudes in Northwest Argentina under contrasting climate conditions (Puna and Chaco Serrano) during high- and low-water periods. The environmental variables that affected Chironomidae community structure were water temperature, conductivity, hardness, current velocity and type of substrate. Fine substrates, gravel and low water temperature favoured cold stenothermal fauna, composed of Orthocladiinae, Diamesinae and Podonominae specimens in the high-altitude streams, whereas warm waters with low conductivity and higher velocity favoured increased species diversity in lowland streams, where there was greater abundance of Chironominae (which corresponds to warm eurythermal fauna). The studied environments belong to a transition zone that should be preserved where cold stenothermic and warm eurythermal Chironomidae overlap.
Subject(s)
Chironomidae , Altitude , Animals , Argentina , Ecosystem , Rivers , TemperatureABSTRACT
Male imagos of Coelotanypus delpontei (Edwards) are redescribed and newly figured and the immature stages are described and figured for the first time. During this study, male imagos of C. mendax (Lynch Arribalzaga) are also redescribed. The specimens were collected from the Paraná and near Uruguay rivers in the Parano-Platense basin.
Subject(s)
Chironomidae , Animals , Argentina , Male , Rivers , South America , UruguayABSTRACT
Male imagos of Pseudochironomus viridis (Kieffer) are redescribed, the immature stages are described and figured for the first time. During this study, larva and pupal exuviae associated to P. richardsoni (Malloch) were recorded for the first time for South America. The specimens were collected from a stream and a river in the Pampasic Hills System in the Chaco Serrano ecoregion of Argentina.
Subject(s)
Chironomidae/classification , Animal Distribution , Animal Structures/anatomy & histology , Animal Structures/growth & development , Animals , Argentina , Body Size , Chironomidae/anatomy & histology , Chironomidae/growth & development , Female , Larva/anatomy & histology , Larva/classification , Larva/growth & development , Male , Organ Size , Pupa/anatomy & histology , Pupa/classification , Pupa/growth & developmentABSTRACT
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.
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.
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.
