CONICET | Buscador de Institutos y Recursos Humanos

The oviposition preference-offspring performance hypothesisproposes that females lay their eggs in habitats that maximize the fitness oftheir offspring. The aim of this study was to assess the oviposition siteselection by Aedes aegypti females and the success of their larvae in habitatswith different detritus accumulation times, under conditions representative ofthe natural spatial variability of detritus quality and quantity in theMetropolitan Area of Buenos Aires, Argentina. Two experiments were performed,one assessing oviposition site selection and the other analyzing developmentalsuccess. In both experiments, two levels of detritus accumulation time werecompared, one with short-time detritus accumulation (2 weeks), and the otherwith long-time detritus accumulation (8 weeks). Naturally fallen detritus wasused in both experiments, collected in ten sites across the Metropolitan Areaof Buenos Aires. In the oviposition experiment, two contiguous ovitrapscorresponding to each accumulation time were placed at each of the ten sites andthe number of eggs received for each treatment was compared. In the developmentexperiment, always 19 larvae were raised in containers of both accumulationtimes and overall performance was compared using an integrated index thatconsiders survival, development time and female size. A large variability inthe amount of detritus collected at the different sites was observed. Thenumber of eggs was significantly higher in the long-time than in the short-time detritusaccumulation containers, and approximately proportional to the amount ofdetritus in each ovitrap. The performance was not affected by the detritusaccumulation time, but a better performance was detected in containers thatreceived a higher amount of organic detritus regardless of the accumulationtime. Leaves were on average the most abundant type of detritus, with anaverage of 53% of the total detritus collected. The amount of leaves added 2weeks before hatching showed a positive effect on larval performance. Ourresults do not support the oviposition preference-offspring performancehypothesis, since Ae. aegypti females laid eggs in containers wherelarvae did not show a better performance. Moreover, at larval densities relatedto the number of eggs actually laid in each of the treatments, it is expectedthat the performance would be even worse in the most selected treatment, due tothe density-dependent effects of crowding. Since the results obtained reflect the natural heterogeneity of theenvironmental conditions in the region studied, they might be a fairly goodindicator of what occurs in natural larval habitats.

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