Effects of Flooding and Temperature on Aedes albifasciatus Development Time and Larval Density in Two Rain Pools at Buenos Aires University City

Aedes albifasciatus is a floodwater mosquito that breeds in temporary waters. This semi-domestic species, widely distributed in Argentina, is a competent vector of the western equine encephalitis. The present study was carried out in two rain pools of the city of Buenos Aires, from April 1998 through March 1999. Samples were taken twice a week during the cold season and daily during the warmer months, starting from October. Immature mosquitoes were collected with a dipper, being the number of dippers proportional to the flooded area. The estimated rainfall thresholds to initiate cohorts of Ae. albifasciatus were: 16-17 mm in the fall-winter period, 25 mm in the spring, and 30 mm in the summer. The development time of the different cohorts and the mean air temperature of their respective periods were estimated in all seasons, ranging from six days (at 24C) to 32 days (at 13C). The equation that best expresses the relationship between development time and mean air temperature is dt =166,27.e-0,1435.T (R2=0,92). Significantly shorter development times were recorded for larvae of the first three stages as compared to the fourth larval stage and pupae

Colonization and Succession of Zooplankton After a Drought: Influence of Hydrology and Free-Floating Plant Dynamics in a Floodplain Lake

We analyzed zooplankton colonization and succession following a temporary drought in a vegetated lake from a floodplain wetland of the Lower Paraná River (Argentina). We took samples of zooplankton and phytoplankton at four habitats of the lake characterized by the presence-absence of emergent or free-floating macrophytes along a 18-month period after the drought. Microzooplankton dominated along the study and macrozooplankton showed seasonal increments in cold seasons. Temporal patterns of broad taxonomic zooplankton groups were associated to hydrology-driven factors, like changes in water depth, conductivity and edible phytoplankton and seasonal changes and not related with free-floating plants. Nevertheless, spatial and temporal patterns of species composition were closely linked to the dynamics of free-floating plants. A clear shift from pelagic to littoral zooplankton taxa was registered when free-floating plants colonized. This study expands the knowledge on the composition and dynamics of zooplankton from floodplain lakes after the disturbance caused by a severe drought. Our results highlight the influence of water level fluctuations as drivers of zooplankton abundance and the joint effect of seasonal changes and free-floating plant dynamics on zooplankton species composition and richness.Fil: Chaparro, Griselda Noemí. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Fontanarrosa, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: O'farrell, Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin