Caffeine and used coffee grounds completely blocked the development of Aedes aegypti in the early stages, in treatments with the concentrations 1.0 mg/mL and 50 mg/mL, respectively. More advanced stages and even adults were obtained in lower concentrations of both substances, enabling observations to be made of mortality rate, longevity and esterase patterns. The experiments involved treatments using either eggs or 3 rd instar larvae (L3), with or without the addition of fish food. Mortality rates prior to the adult stage and adult longevity were significantly different in the comparisons among treatments, in every kind of experiment, but in those using L3 larvae, their percentages were smaller. Observations of the time of larva and adult onset suggested that developmental time was also delayed in treatments with both substances. The addition of fish food increased significantly the number of adults produced in caffeine 0.2 and in the control, but in used coffee grounds, the opposite effect occurred. Longevity was apparently not affected by the addition of food, except again in coffee grounds, in which it decreased. In an attempt to detect a mechanism involved in the action of caffeine and coffee grounds, esterases (enzymes involved in the detoxification of xenobiotics) were analyzed in polyacrylamide gels of treated 4 th instar larvae (L4). In treatments with both substances, the expression of some carboxylesterases was affected, suggesting that they may be involved in the observed impairment.
OBJECTIVE:Previous experiments showed that caffeine blocks the development of Aedes aegypti (Diptera, Culicidae) in the larval stage, consequently inhibiting the production of adults. This study aimed at obtaining data suggestive of caffeine resistance by these mosquitoes. METHODS:Experiments were carried out in successive generations to assess adult production from eggs laid in previous generation and oviposition rate in every generation using 200 and 500 µg/mL caffeine. Tap water was used as control. Experiments were conducted in the city of São José do Rio Preto, Southeastern Brazil between 2002 and 2005. Statistical tests consisted of exploratory data analysis and smoothing algorithms. RESULTS:Increasing reduction in productivity of adults occurred among generations at both caffeine concentrations but the differences were only significant at 200µg/mL caffeine. As for the oviposition rate, there was a decrease in the mean number of eggs per female over generations at both caffeine concentrations. CONCLUSIONS:There was no evidence of caffeine resistance over generations. The study results corroborate caffeine as an alternative as an important Ae. Aegypti control agent to avoid resistance. KEYWORDS: Aedes RESUMOOBJETIVO: Experimentos anteriores mostraram que a cafeína bloqueia o desenvolvimento de Aedes aegypti (Diptera, Culicidae) na fase larval, inibindo conseqüentemente a produção de adultos. O objetivo do estudo foi obter dados que pudessem sugerir desenvolvimento de resistência dos mosquitos à cafeína. MÉTODOS:Foi avaliada a produção de adultos em gerações sucessivas, a partir de ovos produzidos na geração anterior e a taxa de oviposição em cada geração, utilizando meios contendo cafeína a 200 e 500 µg/ml e água de torneira proveniente de poço artesiano como controle.
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