Efficient method for establishing F1 progeny from wild populations of Anopheles mosquitoes

Abstract

BackgroundThe changing malaria situation in Madagascar requires additional knowledge on the physiology and behaviour of local mosquito vectors. However, the absence of established colonies for several anopheline species present in Madagascar constitutes a limiting factor. To avoid labour intensive work and uncertainty for success of establishing Anopheles colonies from Malagasy species, field collections of blood-fed females and in-tube forced oviposition were combined to reliably produce large numbers of F1 progeny.MethodsBlood-fed females were captured in zebu stables or open zebu parks. Oviposition was induced by enclosing gravid females in eppendorf tubes as initially described for Anopheles funestus. The effect of cold anaesthesia on inducing in-tube forced oviposition and on egg yield was assessed for five Anopheles species, namely Anopheles coustani, An. funestus, Anopheles mascarensis, Anopheles arabiensis and Anopheles squamosus. The production of eggs from in-tube forced oviposition and standard egg laying in cages was compared.ResultsFor the five anopheline species studied, the in-tube forced oviposition method had different efficacy ranging from 35.6 to 71.1% females willing to lay eggs in tubes. Interestingly, prior anaesthesia increased significantly the proportion of ovipositing females for An. mascarensis. Prior anaesthesia has a marginal effect on the number of eggs produced. However, the overall yield in eggs collected using the in-tube forced oviposition method largely exceeds the number of eggs that can be produced by females free to oviposit in cages.ConclusionThe efficiency of the method allowed the production of F1 progeny in numbers sufficiently large for developing detailed analyses of the five species tested, including behavioural studies, insecticide resistance assessment and molecular characterization, as well as vector competence studies. It should be applicable to other anopheline species difficult to colonize.

Fitness Characteristics of the Malaria Vector, Anopheles Funestus, During an Attempted Laboratory Colonization

“…A previous study measuring the fecundity of F 1 An. funestus using Madagascan population reported that this species can lay and average of 56 to 108 eggs per mosquito in captivity [35], which corroborate with 65 and 76 eggs from wild-FUTAZ and FUMOZ respectively from the current study. The number of eggs here is consistent to that reported in resistant and susceptible An.…”

“…Therefore, poor hatching observed in the nascent strain (FUTAZ) here is likely due to the low mating success of An. funestus in captivity as has been previously documented in other Anopheles species [35].…”

“…Several attempts have been made to colonize new An. funestus strains [34] from wild populations, but methods used to establish FUMOZ and FANG have not been successful elsewhere [35], including when attempted in the same wild populations where FUMOZ was originally derived (Coetzee personal communication). This inability to repeatedly colonize and establish An.…”

JNK signaling regulates oviposition in the malaria vectorAnopheles gambiae

“…While, to our knowledge, this is the first demonstration that the stress-responsive JNK pathway is involved in an important reproductive behavior such as oviposition, egg laying has been previously linked to stress responses in mosquitoes. Stressful stimuli including heat, dessication, starvation and infection have all been shown to impact on the timing of oviposition (Canyon et al, 1999; Shaw et al, 2016; Sylvestre et al, 2013), whereas confinement stress has been hypothesized to increase the frequency of oviposition in various anophelines (Nepomichene et al, 2017). Links between steroid hormones and stress responses have also been documented (Hirashima et al, 2000; Ishimoto and Kitamoto, 2010; Zheng et al, 2018).…”

Evidence of Insecticide Resistance to Pyrethroids and Bendiocarb in Anopheles funestus from Tsararano, Marovoay District, Madagascar

“…After morphological identification [ 25 ], one hundred and eighty-six (186) blood fed An . funestus were individually transferred into a tube (Eppendorf®) for forced oviposition according to the method described by Nepomichene et al [ 26 ]. In brief, female mosquitoes were maintained at 28°C in 75-80% relative humidity with free access to 10% sucrose until they became fully gravid (about four days) and individually placed inside a tube with a filter paper placed at the bottom.…”