8 research outputs found
Ochlerotatus albifasciatus in rain pools of Buenos Aires: seasonal dynamics and relation to environmental variables
The immature stages of Ochlerotatus albifasciatus develop in temporary pools. The present study aims at evaluating the seasonal dynamics of the aquatic stages of this mosquito, also analyzing the relationship among their presence and breeding success to some relevant climatic and environmental variables in the ephemeral rain pools of an urban park. Nineteen cohorts of O. albifasciatus that developed synchronously after rain events were recorded in all seasons. The proportions of mosquito-positive pools were significantly higher during the fall-winter period than in the spring-summer months (p < 0.001). The presence of this mosquito species was positively related to the amount of rain (p < 0.001), whereas negatively correlated to air temperature (p < 0.05) within a 5.2 to 29.7ºC range. The distribution of the number of cohorts per pool throughout the year was grouped (variance/mean: 3.96), indicating that these habitats were not equally suitable as breeding sites. The immature stages of O. albifasciatus were detected in pools belonging to all of the categories of surface area, depth, duration, vegetation cover, and insolation. However, the proportion of pools where immature mosquitoes were detected was positively and significantly related to surface, depth, duration, and vegetation cover. On the other hand, the proportion of mosquito-positive pools was higher at an intermediate insolation degree. Our results suggest that although preimaginal stages were present in all seasons, high temperatures may be unfavorable to larval development, and substrate vegetation may regulate water temperature. The positive relationship between the proportion of mosquito-positive pools and pool size and duration might reflect a strategy of O. albifasciatus to accomplish immature development
Ochlerotatus albifasciatus in Rain Pools of Buenos Aires: Seasonal Dynamics and Relation to Environmental Variables
The immature stages of Ochlerotatus albifasciatus develop in
temporary pools. The present study aims at evaluating the seasonal
dynamics of the aquatic stages of this mosquito, also analyzing the
relationship among their presence and breeding success to some relevant
climatic and environmental variables in the ephemeral rain pools of an
urban park. Nineteen cohorts of O. albifasciatus that developed
synchronously after rain events were recorded in all seasons. The
proportions of mosquito-positive pools were significantly higher during
the fall-winter period than in the spring-summer months (p < 0.001).
The presence of this mosquito species was positively related to the
amount of rain (p < 0.001), whereas negatively correlated to air
temperature (p < 0.05) within a 5.2 to 29.7ºC range. The
distribution of the number of cohorts per pool throughout the year was
grouped (variance/mean: 3.96), indicating that these habitats were not
equally suitable as breeding sites. The immature stages of O.
albifasciatus were detected in pools belonging to all of the categories
of surface area, depth, duration, vegetation cover, and insolation.
However, the proportion of pools where immature mosquitoes were
detected was positively and significantly related to surface, depth,
duration, and vegetation cover. On the other hand, the proportion of
mosquito-positive pools was higher at an intermediate insolation
degree. Our results suggest that although preimaginal stages were
present in all seasons, high temperatures may be unfavorable to larval
development, and substrate vegetation may regulate water temperature.
The positive relationship between the proportion of mosquito-positive
pools and pool size and duration might reflect a strategy of O.
albifasciatus to accomplish immature development
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