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1.
Genetics ; 227(1)2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38551457

RESUMO

Across diverse insect taxa, the behavior and physiology of females dramatically changes after mating-processes largely triggered by the transfer of seminal proteins from their mates. In the vinegar fly Drosophila melanogaster, the seminal protein sex peptide (SP) decreases the likelihood of female flies remating and causes additional behavioral and physiological changes that promote fertility including increasing egg production. Although SP is only found in the Drosophila genus, its receptor, sex peptide receptor (SPR), is the widely conserved myoinhibitory peptide (MIP) receptor. To test the functional role of SPR in mediating postmating responses in a non-Drosophila dipteran, we generated 2 independent Spr-knockout alleles in the yellow fever mosquito, Aedes aegypti. Although SPR is needed for postmating responses in Drosophila and the cotton bollworm Helicoverpa armigera, Spr mutant Ae. aegypti show completely normal postmating decreases in remating propensity and increases in egg laying. In addition, injection of synthetic SP or accessory gland homogenate from D. melanogaster into virgin female mosquitoes did not elicit these postmating responses. Our results demonstrate that Spr is not required for these canonical postmating responses in Ae. aegypti, indicating that other, as yet unknown, signaling pathways are likely responsible for these behavioral switches in this disease vector.


Assuntos
Aedes , Proteínas de Insetos , Oviposição , Receptores de Peptídeos de Invertebrados , Animais , Feminino , Masculino , Aedes/genética , Aedes/fisiologia , Drosophila melanogaster/fisiologia , Drosophila melanogaster/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Receptores de Peptídeos de Invertebrados/metabolismo , Receptores de Peptídeos de Invertebrados/genética , Comportamento Sexual Animal
3.
J Insect Physiol ; 108: 1-9, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29729859

RESUMO

Aedes aegypti is a vector of medically important viruses including those causing Zika, dengue, and chikungunya. During mating, males transfer a number of proteins and other molecules to the female and these components of the male ejaculate are essential in shifting female post-mating behaviors in a number of insect species. Because these molecules are highly variable by species, and female post-mating behavior by species is also varied, behavioral assays testing the function of the ejaculate are necessary before we can develop control strategies targeting the mating system to reduce mosquito populations. Because increased survival in mosquitoes strongly increases vectorial capacity and can influence population sizes and potential risk we tested the effect of mating on female survival. The ejaculate can either promote or reduce female survival, as both have been shown in multiple insect species, yet this effect has not been directly assessed in mosquitoes. We compared survival of females in four treatment groups: mated females, virgin females, and virgin females injected with either an extract from the male reproductive glands or a saline control. Survival, blood feeding frequency, fecundity and cumulative net reproductive rate (R0) were determined after multiple feedings from a human host. Our results confirm that male reproductive gland substances increase female fecundity and blood feeding frequency, resulting in dramatic increases in fitness (R0). We also demonstrate, for the first time, an effect of male reproductive gland extracts alone on female survival, regardless of whether or not the female ingested a vertebrate blood meal. Thus, the effects of MAG extract on survival are not secondary effects from altered blood feeding. Collectively, we demonstrate a direct role for Ae. aegypti male-derived molecules on increasing female fitness, reproductive success and, ultimately, transmission potential for vector borne pathogens.


Assuntos
Aedes/fisiologia , Genitália Masculina/fisiologia , Comportamento Sexual Animal , Aedes/metabolismo , Animais , Sangue , Ejaculação , Comportamento Alimentar , Feminino , Genitália Masculina/metabolismo , Masculino , Mosquitos Vetores/fisiologia , Reprodução , Açúcares
4.
Malar J ; 16(1): 156, 2017 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-28427415

RESUMO

BACKGROUND: Resistance of malaria vectors to pyrethroid insecticides has been attributed to selection pressure from long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS), and the use of chemicals in agriculture. The use of different classes of insecticides in combination or by rotation has been recommended for resistance management. The aim of this study was to understand the role of IRS with a carbamate insecticide in management of pyrethroid resistance. METHODS: Anopheles mosquitoes were collected from multiple sites in nine districts of Uganda (up to five sites per district). Three districts had been sprayed with bendiocarb. Phenotypic resistance was determined using standard susceptibility tests. Molecular assays were used to determine the frequency of resistance mutations. The kdr L1014S homozygote frequency in Anopheles gambiae s.s. was used as the outcome measure to test the effects of various factors using a logistic regression model. Bendiocarb coverage, annual rainfall, altitude, mosquito collection method, LLIN use, LLINs distributed in the previous 5 years, household use of agricultural pesticides, and malaria prevalence in children 2-9 years old were entered as explanatory variables. RESULTS: Tests with pyrethroid insecticides showed resistance and suspected resistance levels in all districts except Apac (a sprayed district). Bendiocarb resistance was not detected in sprayed sites, but was confirmed in one unsprayed site (Soroti). Anopheles gambiae s.s. collected from areas sprayed with bendiocarb had significantly less kdr homozygosity than those collected from unsprayed areas. Mosquitoes collected indoors as adults had significantly higher frequency of kdr homozygotes than mosquitoes collected as larvae, possibly indicating selective sampling of resistant adults, presumably due to exposure to insecticides inside houses that would disproportionately affect susceptible mosquitoes. The effect of LLIN use on kdr homozygosity was significantly modified by annual rainfall. In areas receiving high rainfall, LLIN use was associated with increased kdr homozygosity and this association weakened as rainfall decreased, indicating more frequency of exposure to pyrethroids in relatively wet areas with high vector density. CONCLUSION: This study suggests that using a carbamate insecticide for IRS in areas with high levels of pyrethroid resistance may reduce kdr frequencies in An. gambiae s.s.


Assuntos
Anopheles/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Mutação de Sentido Incorreto , Fenilcarbamatos/farmacologia , Proteínas de Protozoários/genética , Seleção Genética , Animais , Anopheles/genética , Bioensaio , Feminino , Frequência do Gene , Técnicas de Genotipagem , Humanos , Masculino , Uganda
5.
Malar J ; 15: 44, 2016 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-26821799

RESUMO

BACKGROUND: The distribution of long-lasting insecticidal nets (LLINs) through universal coverage campaigns is a widely adopted approach for the prevention of malaria at scale. While post-distribution surveys play a valuable role in determining cross-sectional levels of LLIN retention and use, as well as frequently cited reasons for non-use, few studies have explored the consistency of LLIN use over time, within the expected lifespan of the net, and the factors which may drive this. METHODS: In this qualitative study, 74 in-depth interviews were conducted with (male) household heads and (female) caregivers of children in LLIN recipient households, as well as community health workers, in Buliisa, Hoima and Kiboga districts in Uganda, 25-29 months following a LLIN mass campaign distribution. A triangulation approach to data analysis was taken, incorporating thematic analysis, most significant change and positive deviance. RESULTS: The factors found to be most influential in encouraging long-term LLIN use were positive experience of net use prior to the distribution, and appreciation or awareness of a range of benefits arising from their use, including protection from malaria as well as importantly, other health, lifestyle, social and economic benefits. Social support from within the community was also identified as an important factor in determining continued use of LLINs. Net use appeared to be more consistent amongst settled urban and rural communities, compared with fishing, pastoralist, refugee and immigrant communities. CONCLUSIONS: A multitude of interplaying factors encouraged consistent LLIN use in this setting. Whilst the protection of malaria remains a powerful motivator, social and behaviour change (SBC) strategies should also capitalize on the non-malaria benefits of net use that provide a long-term rationale for consistent use. Where supplies are available, SBC campaigns should promote replacement options, emphasizing ongoing net care and replacement as a household responsibility, thus reducing dependence on free distributions. The triangulation approach to qualitative data analysis enabled increased confidence in the validity of findings and an enhanced contextual understanding of the factors promoting consistent net use in mid-western Uganda. The approach should be considered when designing future studies to explore factors driving net retention and use trends.


Assuntos
Inseticidas/uso terapêutico , Malária/prevenção & controle , Controle de Mosquitos/estatística & dados numéricos , Mosquiteiros/estatística & dados numéricos , Estudos Transversais , Feminino , Humanos , Mosquiteiros Tratados com Inseticida , Masculino , Uganda
6.
Malar J ; 14: 337, 2015 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-26337671

RESUMO

BACKGROUND: Scale-up of malaria interventions seems to have contributed to a decline in the disease but other factors may also have had some role. Understanding changes in transmission and determinant factors will help to adapt control strategies accordingly. METHODS: Four sites in Ethiopia and Uganda were set up to monitor epidemiological changes and effectiveness of interventions over time. Here, results of a survey during the peak transmission season of 2012 are reported, which will be used as baseline for subsequent surveys and may support adaptation of control strategies. Data on malariometric and entomological variables, socio-economic status (SES) and control coverage were collected. RESULTS: Malaria prevalence varied from 1.4 % in Guba (Ethiopia) to 9.9 % in Butemba (Uganda). The most dominant species was Plasmodium vivax in Ethiopia and Plasmodium falciparum in Uganda. The majority of human-vector contact occurred indoors in Uganda, ranging from 83 % (Anopheles funestus sensu lato) to 93 % (Anopheles gambiae s.l.), which is an important factor for the effectiveness of insecticide-treated nets (ITNs) or indoor residual spraying (IRS). High kdr-L1014S (resistance genotype) frequency was observed in A. gambiae sensu stricto in Uganda. Too few mosquitoes were collected in Ethiopia, so it was not possible to assess vector habits and insecticide resistance levels. ITN ownership did not vary by SES and 56-98 % and 68-78 % of households owned at least one ITN in Ethiopia and Uganda, respectively. In Uganda, 7 % of nets were purchased by households, but the nets were untreated. In three of the four sites, 69-76 % of people with access to ITNs used them. IRS coverage ranged from 84 to 96 % in the three sprayed sites. Half of febrile children in Uganda and three-quarters in Ethiopia for whom treatment was sought received diagnostic tests. High levels of child undernutrition were detected in both countries carrying important implications on child development. In Uganda, 7-8 % of pregnant women took the recommended minimum three doses of intermittent preventive treatment. CONCLUSION: Malaria epidemiology seems to be changing compared to earlier published data, and it is essential to have more data to understand how much of the changes are attributable to interventions and other factors. Regular monitoring will help to better interpret changes, identify determinants, modify strategies and improve targeting to address transmission heterogeneity.


Assuntos
Malária , Adolescente , Adulto , Anemia , Animais , Anopheles , Criança , Pré-Escolar , Estudos Transversais , Etiópia/epidemiologia , Feminino , Febre , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Lactente , Recém-Nascido , Insetos Vetores , Inseticidas , Malária/epidemiologia , Malária/prevenção & controle , Malária/transmissão , Masculino , Desnutrição , Controle de Mosquitos , Plasmodium falciparum , Plasmodium vivax , Gravidez , Complicações na Gravidez , Prevalência , Uganda/epidemiologia , Adulto Jovem
7.
J Insect Physiol ; 58(10): 1307-13, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22796224

RESUMO

Male mosquitoes transfer seminal fluid proteins (hereafter 'SFPs') during mating. These proteins can have profound effects on female behavior in the yellow fever mosquito Aedes aegypti and the Asian tiger mosquito Aedes albopictus. SFPs are thought to be responsible for female refractoriness to mating in both species. However, only limited information is available about the duration of induced refractoriness or the quantity of SFPs required to be effective in Ae. albopictus. Here, we tested the duration of the effect of SFPs on female refractory behavior for both Aedes species. Additionally, we determined the lowest SFP dose required to induce female refractory behavior in Ae. aegypti. Virgin females were injected intra-thoracically with doses ranging from 0.25 to 0.008 equivalents of one male's SFP amount. Our results demonstrate high sensitivity of female Ae. aegypti and Ae. albopictus to SFPs of their own species, with the majority of females becoming refractory at doses ≥ 0.031 male-equivalents after injection into the hemocoel. This effect was long-lasting in both species; none of the injected females were inseminated when presented with males of their own species 30 to 34 days post-injection, whereas most saline-injected control females mated at this time point. These results will aid future work to characterize individual SFPs involved in post-mating refractoriness in these two species. Moreover, they show that as is the situation in the mosquito Anopheles gambiae, and unlike Drosophila melanogaster, sperm are not required for the maintenance of a sexual refractoriness response in Ae. aegypti and Ae. albopictus.


Assuntos
Aedes/fisiologia , Proteínas de Insetos/fisiologia , Proteínas de Plasma Seminal/fisiologia , Comportamento Sexual Animal , Animais , Feminino , Masculino
8.
Am J Trop Med Hyg ; 86(4): 635-41, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22492148

RESUMO

Female Aedes aegypti are assumed to be primarily monandrous (i.e., mate only once in their lifetime), but true estimates of mating frequency have not been determined outside the laboratory. To assess polyandry in Ae. aegypti with first-generation progeny from wild mosquitoes, stable isotope semen-labeled males ((15)N or (13)C) were allowed to mate with unlabeled females in semifield enclosures (22.5 m(3)) in a dengue-endemic area in southern Mexico. On average, 14% of females were positive for both labels, indicating that they received semen from more than one male. Our results provide evidence of a small but potentially significant rate of multiple mating within a 48-hour period and provide an approach for future open-field studies of polyandry in this species. Polyandry has implications for understanding mosquito ecology, evolution, and reproductive behavior as well as genetic strategies for mosquito control.


Assuntos
Aedes/fisiologia , Reprodução/fisiologia , Animais , Dengue/transmissão , Feminino , Masculino , Espectrometria de Massas , México , Controle de Mosquitos , Sêmen
9.
Behav Ecol Sociobiol ; 66(8): 1131-1140, 2012 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-25544799

RESUMO

Sexual harassment studies in insects suggest that females can incur several kinds of costs from male harassment and mating. Here, we examined direct and indirect costs of male harassment on components of female fitness in the predominantly monandrous mosquito Aedes aegypti. To disentangle the costs of harassment versus the costs of mating, we held females at a low or high density with males whose claspers were modified to prevent insemination, and compared these to females held with normal males and to those held with females or alone. A reduced longevity was observed when females were held under high density conditions with males or females, regardless if male claspers had been modified. There was no consistent effect of harassment on female fecundity. Net reproductive rate (R0) was higher in females held at low density with normal males compared to females held with males in the other treatments, even though only a small number of females showed direct evidence of remating. Indirect costs and benefits that were not due to harassment alone were observed. Daughters of females held with normal males at high density had reduced longevity compared to daughters from females held without conspecifics. However, their fitness (R0) was higher compared to females in all other treatments. Overall, our results indicate that A. aegypti females do not suffer a fitness cost from harassment of males when kept at moderate densities, and they suggest the potential for benefits obtained from ejaculate components.

10.
J Med Entomol ; 48(2): 202-11, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21485355

RESUMO

Male reproductive success is dependent on insemination success and reproductive output. During mating, male mosquitoes transfer not just sperm, but also seminal fluid proteins that may have profound effects on mated female biology and behavior. In this study, we investigated the role of male body size and mating history on semen depletion, female longevity, and reproductive success in Aedes aegypti L. Small and large males were mated in rapid succession with up to five females. Our results indicate that large males had greater mating capacity than small males. A reduction in fecundity by >50% was observed in females that were fourth to mate with small males in comparison with females that mated earlier in sequence. For females mated to large males, this reduction became evident for females that mated fifth in sequence. No loss of fertility (measured as hatch rate) was observed in females that were third-fifth in mating sequence compared with females mated to virgin males. When females were maintained on a low-quality (5% sucrose) diet, those mated to virgin males had a greater longevity compared with females mated third in sequence. We conclude that small males experience more rapid seminal depletion than large males, and discuss the role of semen depletion in the mated female. Our results contribute toward a better understanding of the complexity of Ae. aegypti mating biology and provide refined estimates of mating capacity for genetic control efforts.


Assuntos
Aedes/fisiologia , Dengue/transmissão , Insetos Vetores/fisiologia , Animais , Sangue/metabolismo , Tamanho Corporal , Carboidratos/fisiologia , Feminino , Humanos , Larva/fisiologia , Longevidade , Masculino , Reprodução/fisiologia , Sêmen
11.
PLoS Negl Trop Dis ; 5(3): e989, 2011 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-21423647

RESUMO

BACKGROUND: No commercially licensed vaccine or treatment is available for dengue fever, a potentially lethal infection that impacts millions of lives annually. New tools that target mosquito control may reduce vector populations and break the cycle of dengue transmission. Male mosquito seminal fluid proteins (Sfps) are one such target since these proteins, in aggregate, modulate the reproduction and feeding patterns of the dengue vector, Aedes aegypti. As an initial step in identifying new targets for dengue vector control, we sought to identify the suite of proteins that comprise the Ae. aegypti ejaculate and determine which are transferred to females during mating. METHODOLOGY AND PRINCIPAL FINDINGS: Using a stable-isotope labeling method coupled with proteomics to distinguish male- and female-derived proteins, we identified Sfps and sperm proteins transferred from males to females. Sfps were distinguished from sperm proteins by comparing the transferred proteins to sperm-enriched samples derived from testes and seminal vesicles. We identified 93 male-derived Sfps and 52 predicted sperm proteins that are transferred to females during mating. The Sfp protein classes we detected suggest roles in protein activation/inactivation, sperm utilization, and ecdysteroidogenesis. We also discovered that several predicted membrane-bound and intracellular proteins are transferred to females in the seminal fluids, supporting the hypothesis that Ae. aegypti Sfps are released from the accessory gland cells through apocrine secretion, as occurs in mammals. Many of the Ae. aegypti predicted sperm proteins were homologous to Drosophila melanogaster sperm proteins, suggesting conservation of their sperm-related function across Diptera. CONCLUSION AND SIGNIFICANCE: This is the first study to directly identify Sfps transferred from male Ae. aegypti to females. Our data lay the groundwork for future functional analyses to identify individual seminal proteins that may trigger female post-mating changes (e.g., in feeding patterns and egg production). Therefore, identification of these proteins may lead to new approaches for manipulating the reproductive output and vectorial capacity of Ae. aegypti.


Assuntos
Aedes/química , Proteínas de Insetos/análise , Proteoma/análise , Animais , Feminino , Insetos Vetores/química , Masculino , Sêmen/química
12.
Malar J ; 8 Suppl 2: S6, 2009 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-19917076

RESUMO

There is currently renewed interest in assessing the feasibility of the sterile insect technique (SIT) to control African malaria vectors in designated areas. The SIT relies on the sterilization of males before mass release, with sterilization currently being achieved through the use of ionizing radiation. This paper reviews previous work on radiation sterilization of Anopheles mosquitoes. In general, the pupal stage was irradiated due to ease of handling compared to the adult stage. The dose-response curve between the induced sterility and log (dose) was shown to be sigmoid, and there was a marked species difference in radiation sensitivity. Mating competitiveness studies have generally been performed under laboratory conditions. The competitiveness of males irradiated at high doses was relatively poor, but with increasing ratios of sterile males, egg hatch could be lowered effectively. Males irradiated as pupae had a lower competitiveness compared to males irradiated as adults, but the use of partially-sterilizing doses has not been studied extensively. Methods to reduce somatic damage during the irradiation process as well as the use of other agents or techniques to induce sterility are discussed. It is concluded that the optimal radiation dose chosen for insects that are to be released during an SIT programme should ensure a balance between induced sterility of males and their field competitiveness, with competitiveness being determined under (semi-) field conditions. Self-contained 60Co research irradiators remain the most practical irradiators but these are likely to be replaced in the future by a new generation of high output X ray irradiators.


Assuntos
Anopheles/efeitos da radiação , Estágios do Ciclo de Vida/efeitos da radiação , Controle de Mosquitos/métodos , Comportamento Sexual Animal/efeitos da radiação , Animais , Anopheles/fisiologia , Comportamento Competitivo/efeitos da radiação , Relação Dose-Resposta à Radiação , Infertilidade Masculina , Longevidade/efeitos da radiação , Masculino , Radiobiologia , Comportamento Sexual Animal/fisiologia
13.
Acta Trop ; 109(1): 64-9, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18992210

RESUMO

Anopheles mosquitoes are important candidates for genetic control strategies. However, little is known about sperm quality and quantity as determinants of male reproductive success. In this study, sperm quantity and length variation were assessed in testes of un-irradiated and irradiated Anopheles arabiensis. Male reproductive organs were dissected for sperm and an estimate of the total number of spermatozoa was made. Sperm lengths were measured using imaging software. The effects of irradiation were evaluated for males exposed in the pupal or adult stage to a full (120 Gy) or partially sterilising dose (70 Gy). Sperm length variation in the laboratory strain was compared to the distribution observed in wild males. We also determined the size distribution of sperm lengths in spermathecae of inseminated females compared to those observed in male testes. Sperm quantity increased with age, and 12-day-old males had significantly more sperm in their testes (8214+/-467) than males aged 3 days (5022+/-375). Mosquitoes irradiated in the pupal stage had significantly fewer sperm (2982+/-125) than un-irradiated males (4950+/-848) although for adult stage irradiation similar amounts of sperm were observed compared to un-irradiated males. Sperm length variation was detected with sperm lengths ranging between <50 and 500 microm. There were no differences in sperm length distribution compared to wild males. Sperm length distributions were similar to those reported for the closely related sibling species An. gambiae s.s. There was no major effect of irradiation on the distribution of sperm lengths in the testes, with the exception that pupal irradiation resulted in a significant increase in sperm numbers in the category of 100-200 microm. Sperm length distributions in spermathecae were different to those measured directly from sperm in the testes and harboured less cells of the smaller (<100-200 microm), and more cells of the larger category (300-400 microm). The finding that testes of pupal irradiated males produce fewer and smaller sperm in comparison to un-irradiated and adult irradiated testes are discussed in the context of genetic control strategies, in particular the Sterile Insect Technique (SIT).


Assuntos
Anopheles/efeitos da radiação , Malária/parasitologia , Espermatozoides/efeitos da radiação , Animais , Anopheles/citologia , Humanos , Masculino , Contagem de Espermatozoides , Espermatozoides/citologia , Testículo/citologia , Testículo/efeitos da radiação
14.
Malar J ; 7: 65, 2008 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-18439238

RESUMO

BACKGROUND: The work described in this article forms part of a study to suppress a population of the malaria vector Anopheles arabiensis in Northern State, Sudan, with the Sterile Insect Technique. No data have previously been collected on the irradiation and transportation of anopheline mosquitoes in Africa, and the first series of attempts to do this in Sudan are reported here. In addition, experiments in a large field cage under near-natural conditions are described. METHODS: Mosquitoes were irradiated in Khartoum and transported as adults by air to the field site earmarked for future releases (400 km from the laboratory). The field cage was prepared for experiments by creating resting sites with favourable conditions. The mating and survival of (irradiated) laboratory males and field-collected males was studied in the field cage, and two small-scale competition experiments were performed. RESULTS: Minor problems were experienced with the irradiation of insects, mostly associated with the absence of a rearing facility in close proximity to the irradiation source. The small-scale transportation of adult mosquitoes to the release site resulted in minimal mortality (< 6%). Experiments in the field cage showed that mating occurred in high frequencies (i.e. an average of 60% insemination of females after one or two nights of mating), and laboratory reared males (i.e. sixty generations) were able to inseminate wild females at rates comparable to wild males. Based on wing length data, there was no size preference of males for mates. Survival of mosquitoes from the cage, based on recapture after mating, was satisfactory and approximately 60% of the insects were recaptured after one night. Only limited information on male competitiveness was obtained due to problems associated with individual egg laying of small numbers of wild females. CONCLUSION: It is concluded that although conditions are challenging, there are no major obstacles associated with the small-scale irradiation and transportation of insects in the current setting. The field cage is suitable for experiments and studies to test the competitiveness of irradiated males can be pursued. The scaling up of procedures to accommodate much larger numbers of insects needed for a release is the next challenge and recommendations to further implementation of this genetic control strategy are presented.


Assuntos
Anopheles/fisiologia , Anopheles/efeitos da radiação , Raios gama , Insetos Vetores/fisiologia , Insetos Vetores/efeitos da radiação , Controle de Mosquitos/métodos , Animais , Tamanho Corporal , Relação Dose-Resposta à Radiação , Feminino , Fertilidade/efeitos da radiação , Larva , Masculino , Comportamento Sexual Animal , Sudão , Meios de Transporte
15.
J Exp Biol ; 210(Pt 7): 1266-74, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17371925

RESUMO

The potential use of stable isotopes to study mosquito mating was investigated by tracing the fate of labelled semen into spermathecae. [(13)C]glucose was incorporated in the diet of the malaria mosquito Anopheles arabiensis. Treatments included labelling of either the larval water or adult sugar water, or a combination of both. After mating, ;spiked' spermathecae were analysed for isotope ratios using mass spectrometry. Results demonstrated that spermathecae positive for semen could successfully be distinguished from empty ones or controls (i.e. filled with unlabelled semen) using the raw delta(13)C values. Labelling during larval development and combined labelling of larvae and adults resulted in detectable values. The label persisted in spermathecae for up to 7 days after mating, and unlabelled sugar feeding of males labelled in the larval stage did not result in a detectable turnover of the semen label. There were no detrimental effects of the addition of labelled glucose on larval development and survival, adult size, male longevity and mating performance. We have proved that it is possible to label male mosquitoes and detect the semen label in females after insemination. This method offers great potential to study mating in mosquitoes and other insects and could prove useful in genetic control studies of medical or agricultural pest insects, with male mating success in the field as a critical verifiable indicator for a positive outcome of the intervention.


Assuntos
Anopheles/fisiologia , Insetos Vetores/fisiologia , Transporte Espermático/fisiologia , Espermatozoides/metabolismo , Animais , Isótopos de Carbono/análise , Feminino , Genitália Feminina/química , Genitália Feminina/fisiologia , Glucose , Controle de Insetos/métodos , Marcação por Isótopo , Modelos Lineares , Masculino , Espectrometria de Massas , Óvulo/química , Sudão , Análise de Sobrevida
16.
Malar J ; 5: 41, 2006 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-16700906

RESUMO

BACKGROUND: In the context of the Sterile Insect Technique (SIT), radiation-induced sterility in the malaria mosquito Anopheles arabiensis Patton (Diptera: Culicidae) was studied. Male mosquitoes were exposed to gamma rays in the pupal or adult stage and dose-sterility curves were determined. METHODS: Pupae were irradiated shortly before emergence (at 22-26 hrs of age), and adults <24 hrs post emergence. Doses tested ranged between 0 and 100 Gy. The effects of irradiation on adult emergence, male survival, induced sterility and insemination capability were evaluated. Emergence and insemination data were analysed using independent t-tests against the control. Correlation analyses were performed for insemination rate and dose and insemination and fecundity. Male survival was analysed using Kaplan-Meier survival analyses. Finally, the calculated residual fertility values were inverse-normal transformed and linear regression analyses performed. RESULTS: Irradiation of pupae, for all doses tested, had no effect on adult emergence. Survival curves of males irradiated as pupae or adults were similar or even slightly higher than non-irradiated males. Overall, adults appeared to be slightly more susceptible to irradiation, although no significant differences for individual doses were observed. In the pupal stage, a significant negative correlation was found between insemination and dose, but the correlation-coefficient was associated with less than 25% of the total variation. A review of the literature indicated that An. arabiensis is more radiation resistant than other anopheline mosquitoes. CONCLUSION: The optimal dose for male insects to be released in an SIT programme depends on their level of sterility and competitiveness. The use of semi-sterilizing doses to produce more competitive insects is discussed. The most convenient developmental stage for mosquito irradiation on a mass-scale are pupae, but pupal irradiation resulted in a lower insemination rate at the highest dose compared to adult irradiation. On the basis of this study, a suitable dose range that includes semi-sterilizing doses is identified to initiate competitiveness experiments for males irradiated at both developmental stages.


Assuntos
Anopheles/efeitos da radiação , Insetos Vetores/efeitos da radiação , Estágios do Ciclo de Vida/efeitos da radiação , Irradiação Corporal Total/veterinária , Animais , Anopheles/fisiologia , Relação Dose-Resposta à Radiação , Feminino , Fertilidade/efeitos da radiação , Raios gama , Insetos Vetores/fisiologia , Longevidade/efeitos da radiação , Masculino , Pupa/efeitos da radiação , Análise de Regressão , Análise de Sobrevida , Fatores de Tempo , Irradiação Corporal Total/instrumentação
17.
Am Nat ; 166(5): 531-42, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16224719

RESUMO

Within-host competition between coinfecting parasite strains shapes the evolution of parasite phenotypes such as virulence and drug resistance. Although this evolution has a strong theoretical basis, within-host competition has rarely been studied experimentally, particularly in medically relevant pathogens with hosts that have pronounced specific and nonspecific immune responses against coinfecting strains. We investigated multiple infection in malaria, using two pairs of genetically distinct clones of the rodent malaria Plasmodium chabaudi in mice. Clones were inoculated into mice simultaneously or 3 or 11 days apart, and population sizes were tracked using immunofluorescence or quantitative polymerase chain reaction. In all experiments, at least one of the two clones suffered strong competitive suppression, probably through both resource- and immune-mediated (apparent) competition. Clones differed in intrinsic competitive ability, but prior residency was also an important determinant of competitive outcome. When clones infected mice first, they did not suffer from competition, but they did when infecting mice at the same time or after their competitor, more so the later they infected their host. Consequently, clones that are competitively inferior in head-to-head competition can be competitively superior if they infect hosts first. These results are discussed in the light of strain-specific immunity, drug resistance, and virulence evolution theory.


Assuntos
Interações Hospedeiro-Parasita/fisiologia , Malária/fisiopatologia , Plasmodium chabaudi , Animais , Modelos Animais de Doenças , Malária/classificação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Plasmodium chabaudi/classificação , Plasmodium chabaudi/genética , Plasmodium chabaudi/crescimento & desenvolvimento
18.
Proc Natl Acad Sci U S A ; 102(21): 7624-8, 2005 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-15894623

RESUMO

Explaining parasite virulence is a great challenge for evolutionary biology. Intuitively, parasites that depend on their hosts for their survival should be benign to their hosts, yet many parasites cause harm. One explanation for this is that within-host competition favors virulence, with more virulent strains having a competitive advantage in genetically diverse infections. This idea, which is well supported in theory, remains untested empirically. Here we provide evidence that within-host competition does indeed select for high parasite virulence. We examine the rodent malaria Plasmodium chabaudi in laboratory mice, a parasite-host system in which virulence can be easily monitored and competing strains quantified by using strain-specific real-time PCR. As predicted, we found a strong relationship between parasite virulence and competitive ability, so that more virulent strains have a competitive advantage in mixed-strain infections. In transmission experiments, we found that the strain composition of the parasite populations in mosquitoes was directly correlated with the composition of the blood-stage parasite population. Thus, the outcome of within-host competition determined relative transmission success. Our results imply that within-host competition is a major factor driving the evolution of virulence and can explain why many parasites harm their hosts.


Assuntos
Anopheles/parasitologia , Malária/parasitologia , Camundongos/parasitologia , Plasmodium chabaudi/patogenicidade , Animais , Contagem de Eritrócitos , Interações Hospedeiro-Parasita/fisiologia , Malária/transmissão , Plasmodium chabaudi/fisiologia , Reação em Cadeia da Polimerase , Densidade Demográfica , Ratos/parasitologia , Reprodução/fisiologia , Especificidade da Espécie , Virulência
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