Chironomus columbiensis (Diptera: Chironomidae) as test organism for aquatic bioassays: Mass rearing and biological traits.

Chironomidae are aquatic insects that have become a model in laboratory tests to evaluate toxic effect of different pollutants. The use of chironomids as test organisms depends on standard protocols for the rearing under laboratory conditions and expanding knowledge on its biology. We standardize a culture of C. columbiensis and analyze its life cycle under laboratory conditions. The experiments were carried out with different treatments for water, temperature, and food. As a result, a protocol was proposed for the rearing of C. columbiensis under the following conditions: semi-soft and reconstituted water, shredded paper towels as a substrate, soft aeration, temperature of 22 ± 2°C, fed with 0.3 g TetraMin® twice a week and weekly renewal of 50% of the water. Under these conditions, the duration of the life cycle was 17-31 days, with a continuous growth of 1.16 to 14.05 mm in the larval stage and an average of 530 eggs per oviposition. In comparison with other species in the family, this study indicated that C. columbiensis is a species with a short life cycle, sensible to changing conditions (e.g., temperature and food), wide distribution, so is a good organism for being used in aquatic bioassays.

Diversidad de insectos acuáticos en quebradas impactadas por agricultura y minería, Caldas, Colombia / Insect diversity in streams impacted by agriculture and mining, Caldas, Colombia

Resumen Los ecosistemas dulceacuícolas están sometidos a fuertes presiones de tipo antrópico (e.g. agricultura y minería), las cuales ocasionan efectos adversos sobre la diversidad de insectos acuáticos. Se evaluó la comunidad de insectos en quebradas impactadas por agricultura y minería, y se determinó cómo estas actividades afectan a la comunidad. Se estudiaron seis quebradas en Caldas (Colombia), dos impactadas por minería, dos por agricultura y dos quebradas usadas como zonas de referencia. Los insectos fueron recolectados usando una red Surber con tres réplicas por tipo de sustrato (sedimento fino, roca y hojarasca). En total se recolectaron 12 502 insectos acuáticos. Los géneros más representativos fueron: Baetodes, Simulium y Cricotopus (57.7 %). Las quebradas impactadas por agricultura tienen baja diversidad de insectos acuáticos, comparado con las impactadas por minería (F2,309 = 21.82, p = 0.001). La zona agrícola presenta una estructura dominada por Simulium y Cricotopus (Diptera, morfoespecies tolerantes a la contaminación). Baetodes dominó en el sustrato roca, Cricotopus en el sedimento y Simulium y Cricotopus en la hojarasca (F2,309 = 2.84, p = 0.001). Por lo tanto, ambos factores (tipo de impacto y sustrato) son importantes para determinar la diversidad de insectos acuáticos. Nuestros resultados sugieren que la actividad agrícola tiene un mayor impacto sobre la diversidad de insectos acuáticos, los cuales pueden estar asociados con la pérdida de la vegetación ribereña.

Abstract Freshwater ecosystems are under severe anthropic pressure (e.g. agriculture and mining), which generates adverse effects on the diversity of aquatic insects. We evaluated the insect community in streams impacted by agriculture and mining, and determined how these activities affected the community. We studied six streams in Caldas (Colombia), two with mining and two with agriculture impact. We collected the insects using a Surber net with three replicates per substrate (fine sediment, stones, and litter). In total, 12 502 aquatic insects were collected. The most representative genera were Baetodes, Simulium, and Cricotopus (57.7 %). Streams with agricultural activity had lower aquatic insects diversity than mining impact (F2,309 = 21.82, p = 0.001). The agriculture areas presented a structure dominated by Simulium and Cricotopus (Diptera, pollution-tolerant morphospecies). Baetodes dominated in stones substrate, Cricotopus in sediment, and Simulium and Cricotopus dominated in litter (F2,309 = 2.84, p = 0.001). Therefore, both factors (impact and substrate type) are being important in determining the diversity of aquatic insects. Our results suggested that agricultural activity has a higher impact on the diversity of aquatic insects, which may be associated with the loss of riparian vegetation.