Abstract
BackgroundBiological controls with predators of larval mosquito vectors have historically focused almost exclusively on insectivorous animals, with few studies examining predatory plants as potential larvacidal agents. In this study, we experimentally evaluate a generalist plant predator of North America, Utricularia macrorhiza, the common bladderwort, and evaluate its larvacidal efficiency for the mosquito vectors Aedes aegypti and Aedes albopictus in no-choice, laboratory experiments. We sought to determine first, whether U. macrorhiza is a competent predator of container-breeding mosquitoes, and secondly, its predation efficiency for early and late instar larvae of each mosquito species.MethodsNewly hatched, first-instar Ae. albopictus and Ae. aegypti larvae were separately exposed in cohorts of 10 to field-collected U. macrorhiza cuttings. Data on development time and larval survival were collected on a daily basis to ascertain the effectiveness of U. macrorhiza as a larval predator. Survival models were used to assess differences in larval survival between cohorts that were exposed to U. macrorhiza and those that were not. A permutation analysis was used to investigate whether storing U. macrorhiza in laboratory conditions for extended periods of time (1 month vs 6 months) affected its predation efficiency.ResultsOur results indicated a 100% and 95% reduction of survival of Ae. aegypti and Ae. albopictus larvae, respectively, in the presence of U. macrorhiza relative to controls within five days, with peak larvacidal efficiency in plant cuttings from ponds collected in August. Utricularia macrorhiza cuttings, which were prey-deprived, and maintained in laboratory conditions for 6 months were more effective larval predators than cuttings, which were maintained prey-free for 1 month.ConclusionsDue to the combination of high predation efficiency and the unique biological feature of facultative predation, we suggest that U. macrorhiza warrants further development as a method for larval mosquito control.
Highlights
Biological controls with predators of larval mosquito vectors have historically focused almost exclu‐ sively on insectivorous animals, with few studies examining predatory plants as potential larvacidal agents
A non-parametric test of survival hazards comparing predation in experimental cups versus treatments cups shows that predation by U. macrorhiza significantly reduced larval survival (χ2 = 209, df = 1, P < 1 × 10−16)
In this study we evaluated the predation efficiency of U. macrorhiza in two medically important species of Aedes mosquitoes, finding drastic and effective reduction of daily survival for Ae. aegypti and Ae. albopictus larvae in no-choice predation experiments
Summary
Biological controls with predators of larval mosquito vectors have historically focused almost exclu‐ sively on insectivorous animals, with few studies examining predatory plants as potential larvacidal agents. Larvivorous fish have successfully controlled larvae in the genus Anopheles in a variety of habitats worldwide [6,7,8,9,10,11], though they have been less successful in the control of Aedes species [12]. This success is largely attributed to the high predation rates of species such as the mosquito fish, Gambusia affinis and G. holbrooki [13]. Domestic containers are not sustainable habitat for these fish and they must be replenished, a limitation of the overall feasibility of larvivorous fish for sustained control [5]
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