Detection of insemination status in live Aedes aegypti females.
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ABSTRACT:
SUBMITTER: Carrasquilla MC
PROVIDER: S-EPMC4385415 | biostudies-literature | 2015 Apr
REPOSITORIES: biostudies-literature
Publications
Detection of insemination status in live Aedes aegypti females.
Carrasquilla María C MC Lounibos L Philip LP
Journal of insect physiology 20150224
Using the technique described in this report, the presence or absence of sperm in spermathecae of female Aedes aegypti is detectable without dissection. Spermathecae of a lightly anesthetized female can be visualized by phase contrast microscopy through the distended abdomen, after the intersegmental membranes are stretched by ventral placement of a glass cover slip. Most females recovered after the procedure were capable of subsequent reproductive activities. Albeit tedious, this technique pres ...[more]
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Project description:With Aedes aegypti mosquitoes now being released in field programmes aimed at disease suppression, there is interest in identifying factors influencing the mating and invasion success of released mosquitoes. One factor that can increase release success is size: released males may benefit competitively from being larger than their field counterparts. However, there could be a risk in releasing only large males if small field females avoid these males and instead prefer small males. Here we investigate this risk by evaluating mating success for mosquitoes differing in size.We measured mating success indirectly by coupling size with Wolbachia-infected or uninfected mosquitoes and scoring cytoplasmic incompatibility. Large females showed no evidence of a mating preference, whereas small males were relatively more successful than large males when mating with small females, exhibiting an advantage of around 20-25%.Because field females typically encompass a wide range of sizes while laboratory reared (and released) males typically fall into a narrow size range of large mosquitoes, these patterns can influence the success of release programmes which rely on cytoplasmic incompatibility to suppress populations and initiate replacement invasions. Releases could include some small males generated under low food or crowded conditions to counter this issue, although this would need to be weighed against issues associated with costs of producing males of various size classes.
| S-EPMC6090812 | biostudies-other
Project description:Aedes aegypti is the most synanthropic and anthropophilic mosquito of Culicidae. This species always cohabits with humans and is extremely opportunistic. Vector dispersal is directly related to the ability of the females on successfully finding a mate in a generally patchy urban scenario. In the present work, we investigate transcriptional changes in Ae. aegypti females during the courtship process and after mating. We observe a substantial alteration in gene expression triggered just upon contact with Ae. aegypti males, which in turn was not fully correlated to the changes triggered by the contact. After analysing shared significant differentially regulated genes between conspecific contact and insemination, the major part of the observed transcriptomic change triggered by contact is reversed after mating, indicating an intermediary situation between naive and mating conditions that we hypothesize to be crucial for mating success. Upon contact, several chemosensory related genes are repressed, especially odorant binding proteins. Most of these genes return to higher expression rates after mating. None of these genes are significantly regulated by the encounter of a different species, Aedes albopictus. The results presented here might be applied to an innovative control approach focusing on the semiochemical systems of mosquitoes in an effort to disrupt undesirable host-insect interaction to reduce the risk of pathogen transmission to humans.
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Project description:BackgroundAedes aegypti, the main vector of dengue, yellow fever, and other arboviruses thrives in tropical and subtropical areas around the globe putting half of the world's population at risk. Despite aggressive efforts to control the transmission of those viruses, an unacceptable number of cases occur every year, emphasizing the need to develop new control strategies. Proposals for vector control focused on population suppression could offer a feasible alternative method to reduce disease transmission. The induction of extreme male-biased sex ratios has been hypothesized to be able to suppress or collapse a population, with previous experiments showing that stable expression of the male determining factor Nix in A. aegypti is sufficient to convert females into fertile males.Methodology/principal findingsHere, we report on the conditional expression of Nix in transgenic A. aegypti under the control of the tetracycline-dependent (Tet-off) system, with the goal of establishing repressible sex distortion. A masculinization phenotype was observed in three of the seven transgenic lines with females exhibiting male-like long maxillary palps and most importantly, the masculinized females were unable to blood feed. Doxycycline treatment of the transgenic lines only partially restored the normal phenotype from the masculinized transgenic lines, while RT-qPCR analysis of early embryos or adults showed no correlation between the level of masculinization and ectopic Nix expression.Conclusions/significanceWhile the conditional expression of Nix produced intersex phenotypes, the level of expression was insufficient to program full conversion. Modifications that increase both the level of activation (no tet) and the level of repression (with tet) will be necessary, as such this study represents one step forward in the development of genetic strategies to control vector-borne diseases via sex ratio distortion.
| S-EPMC9307153 | biostudies-literature
Project description:BackgroundArboviral diseases, including dengue and chikungunya, are major public health concerns in Bangladesh where there have been unprecedented levels of transmission reported in recent years. The primary approach to control these diseases is to control the vector Aedes aegypti using pyrethroid insecticides. Although chemical control has long been practiced, no comprehensive analysis of Ae. aegypti susceptibility to insecticides has been conducted to date. The aim of this study was to determine the insecticide resistance status of Ae. aegypti in Bangladesh and investigate the role of detoxification enzymes and altered target site sensitivity as resistance mechanisms.MethodsEggs of Aedes mosquitoes were collected using ovitraps from five districts across Bangladesh and in eight neighborhoods of the capital city Dhaka, from August to November 2017. CDC bottle bioassays were conducted for permethrin, deltamethrin, malathion, and bendiocarb using 3- to 5-day-old F0-F2 non-blood-fed female mosquitoes. Biochemical assays were conducted to detect metabolic resistance mechanisms, and real-time PCR was performed to determine the frequencies of the knockdown resistance (kdr) mutations Gly1016, Cys1534, and Leu410.ResultsHigh levels of resistance to permethrin were detected in all Ae. aegypti populations, with mortality ranging from 0 to 14.8% at the diagnostic dose. Substantial resistance continued to be detected against higher (2×) doses of permethrin (5.1-44.4% mortality). Susceptibility to deltamethrin and malathion varied between populations while complete susceptibility to bendiocarb was observed in all populations. Significantly higher levels of esterase and oxidase activity were detected in most of the test populations as compared to the susceptible reference Rockefeller strain. A significant association was detected between permethrin resistance and the presence of Gly1016 and Cys1534 homozygotes. The frequency of kdr (knockdown resistance) alleles varied across the Dhaka Aedes populations. Leu410 was not detected in any of the tested populations.ConclusionsThe detection of widespread pyrethroid resistance and multiple resistance mechanisms highlights the urgency for implementing alternate Ae. aegypti control strategies. In addition, implementing routine monitoring of insecticide resistance in Ae. aegypti in Bangladesh will lead to a greater understanding of susceptibility trends over space and time, thereby enabling the development of improved control strategies.
| S-EPMC7734861 | biostudies-literature
Project description:RNA-Seq was used for transcriptome sequencing of 0-12 hour embryos.
2011-12-16 | GSE34480 | GEO
Project description:BackgroundAedes aegypti and Ae. albopictus are important vectors of infectious diseases, especially those caused by arboviruses such as dengue, chikungunya and Zika. Aedes aegypti is very well adapted to urban environments, whereas Ae. albopictus inhabits more rural settings. Pyrethroid resistance is widespread in these vectors, but limited data exist from the Southwest Pacific Region, especially from Melanesia. While Aedes vector ecology is well documented in Australia, where incursion of Ae. albopictus and pyrethroid resistance have so far been prevented, almost nothing is known about Aedes populations in neighbouring Papua New Guinea (PNG). With pyrethroid resistance documented in parts of Indonesia but not in Australia, it is important to determine the distribution of susceptible and resistant Aedes populations in this region.MethodsThe present study was aimed at assessing Aedes populations for insecticide resistance in Madang and Port Moresby, located on the north and south coasts of PNG, respectively. Mosquitoes were collected using ovitraps and reared in an insectary. Standard WHO bioassays using insecticide-treated filter papers were conducted on a total of 253 Ae. aegypti and 768 Ae. albopictus adult mosquitoes. Subsets of samples from both species (55 Ae. aegypti and 48 Ae. albopictus) were screened for knockdown resistance mutations in the voltage-sensitive sodium channel (Vssc) gene, the target site of pyrethroid insecticides.ResultsHigh levels of resistance against pyrethroids were identified in Ae. aegypti from Madang and Port Moresby. Aedes albopictus exhibited susceptibility to pyrethroids, but moderate levels of resistance to DDT. Mutations associated with pyrethroid resistance were detected in all Ae. aegypti samples screened. Some genotypes found in the present study had been observed previously in Indonesia. No Vssc mutations associated with pyrethroid resistance were found in the Ae. albopictus samples.ConclusionsTo our knowledge, this is the first report of pyrethroid resistance in Ae. aegypti mosquitoes in PNG. Interestingly, usage of insecticides in PNG is low, apart from long-lasting insecticidal nets distributed for malaria control. Further investigations on how these resistant Ae. aegypti mosquito populations arose in PNG and how they are being sustained are warranted.
| S-EPMC6609403 | biostudies-literature
Project description:BackgroundIt was previously demonstrated that alanine aminotransferase (ALAT, EC 2.6.1.2) participates in maintaining the alanine-proline cycle between flight muscles and fat body during Aedes aegypti flight. ALAT is also actively involved in the metabolism of ammonia in A. aegypti. Here, we investigated the survival and behavioral costs of ALAT inhibition in A. aegypti females to better understand the role of ALAT in blood-fed mosquitoes.MethodsWe analyzed how A. aegypti female mosquitoes respond to blood meals supplemented with 0, 2.5, 5 and 10 mM L-cycloserine, a well-known inhibitor of ALAT in animals. Mosquitoes were also exposed to blood meals supplemented with L-cycloserine and different concentrations of glucose (0, 10 and 100 mM). Additionally, the effects of ALAT inhibitor and glucose in mosquitoes starved for 24 or 48 h were investigated. Survival and behavioral phenotypes were analyzed during a time course (1, 2, 4, 6, 12, 24, 48 and 72 h after feeding).ResultsL-cycloserine at 10 mM resulted in high mortality relative to control, with an acute effect during the first 6 h after treatment. A significant decrease in the number of active mosquitoes coinciding with an increase in futile wing fanning during the first 24 h was observed at all inhibitor concentrations. A high occurrence of knockdown phenotype was also recorded at this time for both 5 and 10 mM L-cycloserine. The supplementation of glucose in the blood meal amplified the effects of the ALAT inhibitor. In particular, we observed a higher mortality rate concomitant with an increase in the knockdown phenotype. Starvation prior to blood feeding also increased the effects of L-cycloserine with a rapid increase in mortality.ConclusionsOur results provide evidence that exposure of high doses of L-cycloserine during A. aegypti blood feeding affects mosquito survival and motor activity, suggesting an interference with carbohydrate and ammonia metabolism in a time-dependent manner.
| S-EPMC4261769 | biostudies-literature
Project description:BackgroundAedes aegypti and Ae. albopictus are vectors of numerous arboviruses that adversely affect human health. In mosquito vectors of disease, the bacterial microbiota influence several physiological processes, including fertility and vector competence, making manipulation of the bacterial community a promising method to control mosquito vectors. In this study, we describe the reproductive tract tissue microbiota of lab-reared virgin Ae. aegypti and Ae. albopictus males, and virgin, mated, and mated + blood-fed females of each species, comparing the bacterial composition found there to the well-described gut microbiota.MethodsWe performed metabarcoding of the 16S rRNA isolated from the gut, upper reproductive tract (URT; testes or ovaries), and lower reproductive tract (LRT; males: seminal vesicles and accessory glands; females: oviduct, spermathecae, and bursa) for each species, and evaluated the influence of host species, tissue, nutritional status, and reproductive status on microbiota composition. Finally, based on the identified taxonomic profiles of the tissues assessed, bacterial metabolic pathway abundance was predicted.ResultsThe community structure of the reproductive tract is unique compared to the gut. Asaia is the most prevalent OTU in the LRTs of both Ae. aegypti and Ae. albopictus. In the URT, we observed differences between species, with Wolbachia OTUs being dominant in the Ae. albopictus URT, while Enterobacter and Serratia were dominant in Ae. aegypti URT. Host species and tissue were the best predictors of the community composition compared to reproductive status (i.e., virgin or mated) and nutritional status (i.e., sugar or blood-fed). The predicted functional profile shows changes in the abundance of specific microbial pathways that are associated with mating and blood-feeding, like energy production in mated tissues and siderophore synthesis in blood-fed female tissues.ConclusionsAedes aegypti and Ae. albopictus have distinct differences in the composition of microbiota found in the reproductive tract. The distribution of the bacterial taxonomic groups indicates that some bacteria have tissue-specific tropism for reproductive tract tissue, such as Asaia and Wolbachia. No significant differences in the taxonomic composition were observed in the reproductive tract between virgin, mated, and mated + blood-fed females, but changes in the abundance of specific metabolic pathways were found in the predicted microbial functional profiles in mated and blood-fed females.
| S-EPMC8638121 | biostudies-literature
Project description:BackgroundThe midgut microbiota of mosquitoes maintain basal immune activity and immune priming. In recent years, scientists have focused on the use of microbial communities for vector control interventions. In the present study, the midgut bacteria of larvae and adults of Aedes aegypti and Ae. albopictus were assessed using both field-collected and laboratory-reared mosquitoes from Sri Lanka.MethodsAdults and larvae of Ae. aegypti and Ae. albopictus were collected from three selected areas in Gampaha Medical Officer of Health area, Gampaha District, Western Province, Sri Lanka. Bacterial colonies isolated from mosquito midgut dissections were identified by PCR amplification and sequencing of partial 16S rRNA gene fragments.ResultsAdults and larvae of Ae. aegypti and Ae. albopictus harbored 25 bacterial species. Bacillus endophyticus and Pantoea dispersa were found more frequently in field-collected Ae. aegypti and Ae. albopictus adults, respectively. The midgut bacteria of Ae. aegypti and Ae. albopictus adults (X2 = 556.167, df = 72, P < 0.001) and larvae (X2 = 633.11, df = 66, P < 0.001) were significantly different. There was a significant difference among the bacterial communities between field-collected adults (X2 = 48.974, df = 10, P < 0.001) and larvae (X2 = 84.981, df = 10, P < 0.001). Lysinibacillus sphaericus was a common species in adults and larvae of laboratory-reared Ae. aegypti. Only P. dispersa occurred in the field-collected adults of Ae. aegypti and Ae. albopictus. Species belonging to genera Terribacillus, Lysinibacillus, Agromyces and Kocuria were recorded from Aedes mosquitoes, in accordance with previously reported results.ConclusionsThis study generated a comprehensive database on the culturable bacterial community found in the midgut of field-collected (Ae. aegypti and Ae. albopictus) and laboratory-reared (Ae. aegypti) mosquito larvae and adults from Sri Lanka. Data confirm that the midgut bacterial diversity in the studied mosquitoes varies according to species, developmental stage and strain (field vs laboratory).
| S-EPMC8400895 | biostudies-literature
Project description:BackgroundWhen the first systematic list of mosquitoes in Nepal was reported in 1990, there was no description of Aedes aegypti (L.), while Aedes albopictus (Skuse) has been included in the Stegomyia subgroup since the 1950s. The first record of Ae. aegypti in Nepal was reported in 2009, suggesting some coincidence between the invasion of this species and the first record of dengue fever in Nepal in 2006.ResultsWe performed a field survey of the distribution and insecticide susceptibility of Ae. aegypti and Ae. albopictus in Nepal in 2017 and 2018. Mosquito larvae were collected from used tires located along the streets of Kathmandu, Bharatpur and Pokhara, and a simplified bioassay was used to assess the susceptibility of the larvae to pyrethroid insecticides using d-allethrin. The presence or absence of point mutations in the voltage-gated sodium channel was also detected by direct sequencing. V1016G was detected at a high frequency and a strong correlation was observed between the frequencies of V1016G and susceptibility indices in Ae. aegypti populations. F1534C was also detected at a relatively low frequency. In Ae. albopictus populations, susceptibilities to d-allethrin were high and no point mutations were detected. Analysis of the cytochrome c oxidase subunit 1 (cox1) gene was performed for assessing genetic diversity and the existence of two strains were identified in Ae. aegypti populations. One consisted of 9 globally-distributed haplotypes while the other was derived from an African haplotype.ConclusionsThe high pyrethroid resistance, high V1016G frequency, and relatively low quantity of insecticides used to control dengue vectors in Nepal may have resulted in only weak selection pressure favoring insecticide resistance and could support the hypothesis that this species has recently been introduced from neighboring Asian countries where pyrethroid resistance is relatively widespread.
| S-EPMC7178601 | biostudies-literature