Embryonic desiccation resistance in Aedes aegypti: presumptive role of the chitinized Serosal Cuticle

<p>Abstract</p> <p>Background</p> <p>One of the major problems concerning dengue transmission is that embryos of its main vector, the mosquito <it>Aedes aegypti</it>, resist desiccation, surviving several months under dry conditions. The serosal cuticle (SC) contributes to mosquito egg desiccation resistance, but the kinetics of SC secretion during embryogenesis is unknown. It has been argued that mosquito SC contains chitin as one of its components, however conclusive evidence is still missing.</p> <p>Results</p> <p>We observed an abrupt acquisition of desiccation resistance during <it>Ae. aegypti </it>embryogenesis associated with serosal cuticle secretion, occurring at complete germ band extension, between 11 and 13 hours after egglaying. After SC formation embryos are viable on dry for at least several days. The presence of chitin as one of the SC constituents was confirmed through Calcofluor and WGA labeling and chitin quantitation. The <it>Ae. aegypti </it>Chitin Synthase A gene (<it>AaCHS1</it>) possesses two alternatively spliced variants, <it>AaCHS1a </it>and <it>AaCHS1b</it>, differentially expressed during <it>Ae. aegypti </it>embryonic development. It was verified that at the moment of serosal cuticle formation, <it>AaCHS1a </it>is the sole variant specifically expressed.</p> <p>Conclusion</p> <p>In addition to the peritrophic matrix and exoskeleton, these findings confirm chitin is also present in the mosquito serosal cuticle. They also point to the role of the chitinized SC in the desiccation resistance of <it>Ae. aegypti </it>eggs. <it>AaCHS1a </it>expression would be responsible for SC chitin synthesis. With this embryological approach we expect to shed new light regarding this important physiological process related to the <it>Ae. aegypti </it>life cycle.</p

New molecular markers for phlebotomine sand flies

Using degenerate-primers PCR we isolated and sequenced fragments from the sand fly Lutzomyia longipalpis homologous to two behavioural genes in Drosophila, cacophony and period. In addition we identified a number of other gene fragments that show homology to genes previously cloned in Drosophila. A codon usage table for L. longipalpis based on these and other genes was calculated. These new molecular markers will be useful in population genetics and evolutionary studies in phlebotomine sand flies and in establishing a preliminary genetic map in these important leishmaniasis vectors.info:eu-repo/semantics/submittedVersio

Evaluation of methoprene effect on Aedes aegypti (Diptera: Culicidae) development in laboratory conditions

Several Brazilian Aedes aegypti   populations are resistant to the larvicidae temephos. Methoprene, that inhibits adult emergence, is one of the alternatives envisaged by the Brazilian Dengue Control Program (PNCD). However, at Brazil vector infestation rates are measured through larvae indexes and it has been claimed that methoprene use in the field could face operational problems. In order to define a standardized protocol, methoprene effect was evaluated in laboratory conditions after continuous exposure of larvae (Rockefeller strain) to a methoprene formulation available to the PNCD. Methoprene-derived mortality occurs mainly at the pupa stage and pupa development is inversely proportional to methoprene concentration. Number and viability of eggs laid by treated and control females are equivalent. A methoprene dose-dependent delay in the development was noted; however, strong correlations were found for total mortality or adult emergence inhibition if data obtained when all control mosquitoes have emerged are compared to data obtained when methoprene-treated groups finish development. The cumulative record of total methoprene-induced mortality at the time control adults emerge is proposed for routine evaluation of field populations. Mortality of all specimens, but not of larva, could account for adult emergence inhibition, confirming the inadequacy of larvae indexes to evaluate methoprene effect

Circadian clock of Aedes aegypti: effects of blood-feeding, insemination and RNA interference

Made available in DSpace on 2015-08-19T13:49:33Z (GMT). No. of bitstreams: 2 license.txt: 1914 bytes, checksum: 7d48279ffeed55da8dfe2f8e81f3b81f (MD5) samira_ehlers_etal_IOC_2013.pdf: 287581 bytes, checksum: 8e5f11fa5eb89fad2b4b95b764ca65fa (MD5) Previous issue date: 2013Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular. Rio de Janeiro, RJ, Brasil.Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, Brasil / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. 3Laboratório de Fisiologia e Controle de Artrópodes Vetores. Rio de Janeiro, RJ, Brasil / Instituto de Biologia do Exército. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular. Rio de Janeiro, RJ, Brasil / Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, BraFundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular. Rio de Janeiro, RJ, Brasil / Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, BraMosquitoes are the culprits of some of the most important vector borne diseases. A species’ potential as a vector is directly dependent on their pattern of behaviour, which is known to change according to the female’s physiological status such as whether the female is virgin/mated and unfed/blood-fed. However, the molecular mechanism triggered by and/or responsible for such modulations in behaviour is poorly understood. Clock genes are known to be responsible for the control of circadian behaviour in several species. Here we investigate the impact mating and blood-feeding have upon the expression of these genes in the mosquito Aedes aegypti. We show that blood intake, but not insemination, is responsible for the down-regulation of clock genes. Using RNA interference, we observe a slight reduction in the evening activity peak in the fourth day after dstim injection. These data suggest that, as in Drosophila, clock gene expression, circadian behaviour and environmental light regimens are interconnected in Ae. aegypti

Effect of the chitin synthesis inhibitor triflumuron on the development, viability and reproduction of Aedes aegypti

The control of Aedes aegypti is impaired due to the development of resistance to chemical insecticides. Insect Growth Regulators (IGR) exhibit distinct mechanisms of action and are considered potential vector control alternatives. Studies regarding the effects of sublethal IGR doses on the viability of resulting adults will contribute to eval-uating their impact in the field. We analyzed several aspects of Ae. aegypti adults surviving exposure to a partially lethal dose of triflumuron, a chitin synthesis inhibitor. A highly significant difference in the proportion of males and females was noted in the triflumuron-exposed group (65.0% males) compared to the controls (50.2% males). Triflumuron affected adult longevity, particularly for females; after 16 days, only 29.2% of males and 13.8% of females were alive, in contrast with 94% survival of the control mosquitoes. The locomotor activity was reduced and the blood-feeding ability of the treated females was also affected (90.4% and 48.4% of the control and triflumuron-exposed females, respectively, successfully ingested blood). Triflumuron-surviving females ingested roughly 30% less blood and laid 25% fewer eggs than the control females. The treated males and females exhibited a diminished ability to copulate, resulting in less viable eggs

Potential impact of a presumed increase in the biting activity of dengue-virus-infected Aedes aegypti (Diptera: Culicidae) females on virus transmission dynamic

Submitted by Sandra Infurna ([email protected]) on 2016-10-11T17:12:52Z No. of bitstreams: 1 tamara_camara_etal_IOC_2011.pdf: 1096351 bytes, checksum: c4842b4973dba5ae0fa933b65b8ce3c0 (MD5)Approved for entry into archive by Sandra Infurna ([email protected]) on 2016-10-11T17:22:48Z (GMT) No. of bitstreams: 1 tamara_camara_etal_IOC_2011.pdf: 1096351 bytes, checksum: c4842b4973dba5ae0fa933b65b8ce3c0 (MD5)Made available in DSpace on 2016-10-11T17:22:48Z (GMT). No. of bitstreams: 1 tamara_camara_etal_IOC_2011.pdf: 1096351 bytes, checksum: c4842b4973dba5ae0fa933b65b8ce3c0 (MD5) Previous issue date: 2011Fundação Oswaldo Cruz. Instituto de Pesquisa Clínica Evandro Chagas. Laboratório de Pesquisa Clínica em DST & AIDS. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Transmissores de Hematozoários. Rio de Janeiro, RJ, Brasil.Universidade Federal do Rio de Janeiro (UFRJ). Instituto de Bioquímica Médica. Programa de Biologia Molecular e Biotecnologia. Rio de Janeiro, RJ, Brasil / Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Transmissores de Hematozoários. Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular de Insetos. Rio de Janeiro, RJ, Brasil. / Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Rio de Janeiro, RJ, Brasil.Recently, we showed that infection with dengue virus increases the locomotor activity of Aedes aegypti females. We speculate that the observed increased locomotor activity could potentially increase the chances of finding a suitable host and, as a consequence, the relative biting rate of infected mosquitoes. We used a mathematical model to investigate the impact of the increased locomotor activity by assuming that this activity translated into an increased biting rate for infected mosquitoes. The results show that the increased biting rate resulted in dengue outbreaks with greater numbers of primary and secondary infections and with more severe biennial epidemics

Molecular evolution of the period gene in sandflies

The molecular evolution of the clock gene period was studied in Phlebotomine sandflies (Diptera: Psychodidae). Comparison of the synonymous and nonsynonymous substitution rates between sandflies and Drosophila revealed a significantly higher evolutionary rate in the latter in three of the four regions analyzed. The differences in rate were higher in the sequences flanking the Thr-Gly repetitive domain, a region that has expanded in Drosophila but remained stable and short in sandflies, a result consistent with the coevolutionary scenario proposed for this region of the gene. An initial phylogenetic analysis including eight neotropical sandfly species and one from the Old World was also carried out. The results showed that only the subgenus Nyssomyia is well supported by distance (neighbor-joining) and maximum parsimony analysis. The grouping of the other species from the subgenus Lutzomyia and Migonei group shows very low boot-strap values and is not entirely consistent with classical morphological systematics of the genus Lutzomyia