Egg hatching, larval movement and larval survival of the malaria vector Anopheles gambiae in desiccating habitats

Koenraadt, Constantianus J. M.; Paaijmans, Krijn P.; Githeko, Andrew K.; Knols, Bart G. J.; Takken, Willem

doi:10.1186/1475-2875-2-20

Cited by 59 publications

(24 citation statements)

References 23 publications

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“…Until recently, aestivation in African anophelines has been discounted by most entomologists, although winter diapause in temperate malaria vectors has been well-documented (Jetten and Takken, 1994), and a few studies provided evidence consistent with it in Sudan (Omer and Cloudsley-Thompson, 1968, 1970). In part, this stemmed from studies conducted in areas that experience a “mild dry season,” during which some larval sites remain available within 5-10 km radius (Charlwood et al, 2000; Jawara et al, 2008; Koenraadt et al, 2003; Minakawa et al, 2001; Ramsdale and Fontaine, 1970a, b; Sogoba et al, 2007). Although less abundant, constantly available larval sites during the dry season probably act as a strong selection force against aestivation.…”

Section: Discussionmentioning

confidence: 99%

Ecophysiology of Anopheles gambiae s.l.: Persistence in the Sahel

Huestis

Lehmann

2014

Infection, Genetics and Evolution

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The dry-season biology of malaria vectors is poorly understood, especially in arid environments when no surface waters are available for several months, such as during the dry season in the Sahel. Here we reappraise results on the dry-season physiology of members of the Anopheles gambiae s.l. complex in the broad context of dormancy in insects and especially in mosquitoes. We examine evidence on seasonal changes in reproduction, metabolism, stress tolerance, nutrition, molecular regulation, and environmental conditions and determine if the current results are compatible with dry-season diapause (aestivation) as the primary strategy for persistence throughout the dry season in the Sahel. In the process, we point out critical gaps in our knowledge that future studies can fill. We find compelling evidence that members of the An. gambiae s.l. complex undergo a form of aestivation during the Sahelian dry season by shifting energetic resources away from reproduction and towards increased longevity. Considering the differences between winter at temperate latitudes, which entails immobility of the insect and hence reliance on physiological solutions, as opposed to the Sahelian dry season, which restricts reproduction exclusively, we propose that behavioral changes play an important role in complementing physiological changes in this strategy.

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Section: Discussionmentioning

confidence: 99%

Ecophysiology of Anopheles gambiae s.l.: Persistence in the Sahel

Huestis

Lehmann

2014

Infection, Genetics and Evolution

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“…The daily mortality rate for eggs assumes that approximately half (~51%) of eggs hatch after 3 days, below the estimated hatch rate in controlled laboratory conditions [47] to account for predation. While the daily mortality rate for eggs is fixed (d e = 0.2) and age-dependent for adults (see below), we incorporate density dependence in larval mortality as a sigmoidal increase with the larval population size (S3D Fig): where d l min = 0.035 [57] is the baseline daily larval mortality rate, d l max = 0.4 is the maximum daily larval morality [57], n l is the total number of larvae, K = 10 4 is the equilibrium larval population size under no intervention, and the shape of the function is determined by the constants: c 1 = 0.05 to begin at the baseline daily mortality rate; c 2 = 3.4 to control steepness of the curve, and c 3 = 2 to control position of the curve, were chosen so the mortality rate at a population size of K results in exact replacement.…”

Section: Methodsmentioning

confidence: 99%

Disrupting Mosquito Reproduction and Parasite Development for Malaria Control

et al. 2016

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The control of mosquito populations with insecticide treated bed nets and indoor residual sprays remains the cornerstone of malaria reduction and elimination programs. In light of widespread insecticide resistance in mosquitoes, however, alternative strategies for reducing transmission by the mosquito vector are urgently needed, including the identification of safe compounds that affect vectorial capacity via mechanisms that differ from fast-acting insecticides. Here, we show that compounds targeting steroid hormone signaling disrupt multiple biological processes that are key to the ability of mosquitoes to transmit malaria. When an agonist of the steroid hormone 20-hydroxyecdysone (20E) is applied to Anopheles gambiae females, which are the dominant malaria mosquito vector in Sub Saharan Africa, it substantially shortens lifespan, prevents insemination and egg production, and significantly blocks Plasmodium falciparum development, three components that are crucial to malaria transmission. Modeling the impact of these effects on Anopheles population dynamics and Plasmodium transmission predicts that disrupting steroid hormone signaling using 20E agonists would affect malaria transmission to a similar extent as insecticides. Manipulating 20E pathways therefore provides a powerful new approach to tackle malaria transmission by the mosquito vector, particularly in areas affected by the spread of insecticide resistance.

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“…Meanwhile, investigations of population genetics ruled out severe demographic bottlenecks in areas with strong seasonal fluctuations on the abundance of these mosquitoes. These results suggest that a significant number of adult specimens survive locally during the dry season (Simard et al, 2000;Taylor et al, 1993), as the pre-imaginal stages (eggs, larvae and pupae) are not able to survive without water (Koenraadt et al, 2003;Minakawa et al, 2001). Hence, it was generally proposed that mosquito populations can be maintained in large numbers during the dry season via aestivating females that do not reproduce (Holstein, 1954;Lehmann et al, 2010;Omer and Cloudsley-Thompson, 1970), and thus survive the challenging desiccating environmental conditions.…”

Section: Introductionmentioning

confidence: 90%

Novel insights into the metabolic and biochemical underpinnings assisting dry-season survival in female malaria mosquitoes of the Anopheles gambiae complex

Hidalgo¹,

Mouline²,

Mamaï³

et al. 2014

Journal of Insect Physiology

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The mechanisms by which Anopheles gambiae mosquitoes survive the desiccating conditions of the dry season in Africa and are able to readily transmit malaria soon after the rains start remain largely unknown. The desiccation tolerance and resistance of female An. gambiae M and S reared in contrasting environmental conditions reflecting the onset of dry season ("ods") and the rainy season ("rs") was determined by monitoring their survival and body water loss in response to low relative humidity. Furthermore, we investigated the degree to which the physiology of 1-h and 24-h-old females is altered at "ods" by examining and comparing their quantitative metabotypes and proteotypes with conspecifics exposed to "rs" conditions. Results showed that distinct biochemical rearrangements occurred soon after emergence in female mosquitoes that enhance survival and limit water loss under dry conditions. In particular, three amino acids (phenylalanine, tyrosine, and valine) playing a pivotal role in cuticle permeability decreased significantly from the 1-h to 24-h-old females, regardless of the experimental conditions. However, these amino acids were present in higher amounts in 1-h-old female An. gambiae M reared under "ods" whereas no such seasonal difference was reported in S ones. Together with the 1.28- to 2.84-fold increased expression of cuticular proteins 70 and 117, our data suggests that cuticle composition, rigidity and permeability were adjusted at "ods". Increased expression of enzymes involved in glycogenolytic and proteolytic processes were found in both forms at "ods". Moreover, 1-h-old S forms were characterised by elevated amounts of glycogen phosphorylase, isocitrate dehydrogenase, and citrate synthase, suggesting an increase of energetic demand in these females at "ods".

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Egg hatching, larval movement and larval survival of the malaria vector Anopheles gambiae in desiccating habitats

Abstract: Background: Although the effects of rainfall on the population dynamics of the malaria vector Anopheles gambiae have been studied in great detail, the effects of dry periods on its survival remain less clear.

Cited by 59 publications

References 23 publications

Ecophysiology of Anopheles gambiae s.l.: Persistence in the Sahel

Ecophysiology of Anopheles gambiae s.l.: Persistence in the Sahel

Disrupting Mosquito Reproduction and Parasite Development for Malaria Control

Novel insights into the metabolic and biochemical underpinnings assisting dry-season survival in female malaria mosquitoes of the Anopheles gambiae complex

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