Survival and swimming behavior of insecticide-exposed larvae and pupae of the yellow fever mosquito Aedes aegypti

Abstract

BackgroundThe yellow fever mosquito Aedes aegypti is essentially a container-inhabiting species that is closely associated with urban areas. This species is a vector of human pathogens, including dengue and yellow fever viruses, and its control is of paramount importance for disease prevention. Insecticide use against mosquito juvenile stages (i.e. larvae and pupae) is growing in importance, particularly due to the ever-growing problems of resistance to adult-targeted insecticides and human safety concerns regarding such use in human dwellings. However, insecticide effects on insects in general and mosquitoes in particular primarily focus on their lethal effects. Thus, sublethal effects of such compounds in mosquito juveniles may have important effects on their environmental prevalence. In this study, we assessed the survival and swimming behavior of A. aegypti 4th instar larvae (L4) and pupae exposed to increasing concentrations of insecticides. We also assessed cell death in the neuromuscular system of juveniles.MethodsThird instar larvae of A. aegypti were exposed to different concentrations of azadirachtin, deltamethrin, imidacloprid and spinosad. Insect survival was assessed for 10 days. The distance swam, the resting time and the time spent in slow swimming were assessed in 4th instar larvae (L4) and pupae. Muscular and nervous cells of L4 and pupae exposed to insecticides were marked with the TUNEL reaction. The results from the survival bioassays were subjected to survival analysis while the swimming behavioral data were subjected to analyses of covariance, complemented with a regression analysis.ResultsAll insecticides exhibited concentration-dependent effects on survival of larvae and pupae of the yellow fever mosquito. The pyrethroid deltamethrin was the most toxic insecticide followed by spinosad, imidacloprid, and azadirachtin, which exhibited low potency against the juveniles. All insecticides except azadirachtin reduced L4 swimming speed and wriggling movements. A similar trend was also observed for swimming pupa, except for imidacloprid, which increased the swimming activity of pupa. Curiously, the insecticides did not affect cell damage in the neuromuscular system of larvae and pupae.ConclusionsDeltamethrin and spinosad were the main compounds to exhibit lethal effects, which allowed the control of A. aegypti larvae and pupae, and impair their swimming potentially compromising foraging and predation likelihood.

Deltamethrin toxicity and impaired swimming behavior of two backswimmer species

“…The susceptibility of aquatic insects to insecticides is related to physiological and behavioral constraints associated with aquatic ecosystems . In the present study we demonstrated that 2 phylogenetically related backswimmer species ( B. tarsalis and M. bentoi ) had different susceptibilities to deltamethrin, which also had effects on individual swimming activities.…”

“…A common deltamethrin‐mediated behavioral impairment in arthropods is a decrease in locomotor activity , with consequent severe reductions in feeding and antipredator activities that lead to changes in survival (avoiding predators) or reproductive success . In the present study, short‐term exposure to deltamethrin was sufficient to alter individual (but not group) swimming activities (e.g., natural pattern of occupancy in the water column and resting time) in B. tarsalis , but not in M. bentoi .…”

Imidacloprid impairs the post‐embryonic development of the midgut in the yellow fever mosquito Stegomyia aegypti (=Aedes aegypti)

“…However, little information is available about its effects on St. aegypti (Antonio-Arreola et al, 2011). Although imidacloprid has low activity against larvae and pupae compared with other insecticides, its sub-lethal effects may be important in reducing populations of St. aegypti (Tomé et al, 2014).…”

Neurotoxic Zanthoxylum chalybeum root constituents invoke mosquito larval growth retardation through ecdysteroidogenic CYP450s transcriptional perturbations

“…Perturbed acetylcholinesterase (AChE) activity linked to larval lethality Transient exposure of mosquito larvae to ZCE and its bioactive fraction for <5 h exhibited no obvious morphological aberrations but drastically reduced larval swimming behavior, induced muscle paralysis and immobilization leading to death. These observations are closely linked to neuromuscular toxicity effects reported by Tomé et al [45]. To ascertain whether the observed acute toxicity on mosquito larvae was as a result of suppressive effects of ZCE and its bioactive fraction on AChE, we performed the biochemical colorimetric Ellman's enzymatic assay and RT-qPCR gene expression analysis.…”