Showing papers by "Gustavo Ferreira Martins published in 2014"

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

Abstract: The 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. Third 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. All 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. Deltamethrin 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.

Are mitochondrial lineages, mitochondrial lysis and respiration rate associated with phosphine susceptibility in the maize weevil Sitophilus zeamais?

Abstract: Phosphine is the most widely used fumigant with ever-growing problems of phosphine resistance among insect pests of stored products. One such insect is the maize weevil Sitophilus zeamais, a key pest of stored cereals. Despite its importance as a fumigant, the mechanisms of phosphine toxicity and resistance remain unclear, although the mitochondrion is broadly recognised as its site of action. Here we explored the phosphine susceptibility of maize weevil populations and its association with insect respiration rate, and we tested the association of phosphine susceptibility with the mitochondrial lineages from the field populations studied. We also assessed the action of phosphine in the degradation of mitochondria from muscle cells. Survival under phosphine treatment varied among weevil populations and was negatively correlated with the respiration rate and body mass of the insect. Phosphine produced little lysis of mitochondria and the more phosphine-resistant population exhibited a slightly higher mitochondria fluorescence intensity under confocal imaging. Therefore, reduced respiration rate is correlated with reduced phosphine activity, but its association with high mitochondria fluorescence intensity in muscle cells seems marginal. There was no association between mitochondrial lineages and phosphine susceptibility, which evolved independently, and the mitochondrial gene fragments of cytochrome oxidase I and II were not useful molecular markers of phosphine susceptibility.

The antennal sensilla of Melipona quadrifasciata (Hymenoptera: Apidae: Meliponini): a study of different sexes and castes

Abstract: The sensilla of insects are integumental units that play a role as sensory structures and are crucial for the perception of stimuli and for communication. In this study, we compared the antennal sensilla of females (workers and queens), males (haploid (n) and diploid (2n)), and queen-like males (QLMs, resulting from 2n males after juvenile hormone (JH) treatment) in the stingless bee Melipona quadrifasciata. Images of the dorsal antenna surfaces were acquired using a scanning electron microscope. As reported for other hymenopterans, this species exhibits a heterogeneous sensillar distribution along the antennae. Thirteen different types of sensilla were found in the antennae of M. quadrifasciata: trichodea (subtypes I to VI), chaetica (subtypes I and II), placodea, basiconica, ampullacea, coeloconica, and coelocapitula. Sensilla trichodea I were the most abundant, followed by sensilla placodea, which might function in olfactory perception. Sensilla basiconica, sensilla chaetica I, sensilla coeloconica, and sensilla ampullacea were found exclusively in females. In terms of the composition and size of the sensilla, the antennae of QLMs most closely resemble those of the 2n male, although QLMs exhibit a queen phenotype. This study represents the first comparative analysis of the antennal sensilla of M. quadrifasciata. The differences found in the type and amount of sensilla between the castes and sexes are discussed based on the presumed sensillary functions.

Age-mediated and environmentally mediated brain and behavior plasticity in the stingless bee Melipona quadrifasciata anthidioides

Abstract: Structural changes in the insect brain related to age and individual experience may underlie the behavioral plasticity that is particularly important in such social insects as bees. This study assessed the influence of age and rearing conditions (field vs laboratory) in mediating changes in the volume of mushroom bodies and antennal lobes in the brains of workers of the native stingless bee Melipona quadrifasciata anthidioides Lepeletier, a pollinator species with small colonies exhibiting high level of sociability and behavioral versatility. Although only age-dependent enlargement was observed in the antennal lobes, significant increase (21 %) in the neuropils of the mushroom bodies occurred before the foraging age, in contrast to honeybees, and environmental complexity led to a significant increase in both the mushroom body volume and the walking activity. Such differences in the stingless bee M. quadrifasciata anthidioides as compared with the honeybee may assist in relating brain evolution and plasticity with the behavior in these social insects.

Insights Into the Proteome of the Spermatheca of the Leaf-Cutting Ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Abstract: Summary Fifteen of the 22 differentially expressed proteins in the spermathecae of virgin and inseminated females of the leaf cutting ant Atta sexdens rubropilosa were tentatively identified. The profile of expressed proteins of the spermatheca differed significantly between virgin and fertilized females. Data from this study should contribute to the elucidation of the roles of these various proteins in prolonged storage and maintenance of viable spermatozoa within the female.