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1.
Abstract. The name Anopheles bwambae is proposed for the taxon previously called species D of the An.gambiae complex. This sibling species is known only from the vicinity of Buranga hot springs in Bwamba County, Toro District, Uganda, where it breeds in brackish water from geothermal springs together with other halophilic mosquitoes (Ae.albocephalus, Ae.natwnius, Cx.tenagius). An.bwambae adults inhabit the Semliki Forest, where the natural hosts are unknown, but they also enter houses in nearby villages and bite human beings avidly. Plasmodium sporozoites and developing larvae of Wuchereria bancrofti were found in An.bwambae females, so it is assumed that this species of vector contributes locally to transmission of human malaria and filariasis (together with An.funestus, An.gambiae and An.arabiensis). The specific diagnosis of An.bwambae depends upon (i) the presence of fixed inversion 3La and polymorphic inversions 2R1 and 3Rb of the karyotype, as interpreted from ovarian polytene chromosomes, (ii) a fast fixed allozyme of super-oxide dismutase (Sod-105), (iii) female palpi with broader pale apical band and narrower dark sub-apical band than for other sibling species. Cytotaxonomically An.bwambae has the same X-chromosome banding pattern as An.quadriannulatus and An.melas; the latter also has autosomal inversion 3La and therefore appears to be the sister-species of An.bwambae. An identification key is given to the six named sibling species of the An.gambiae complex.  相似文献   

2.
1. Anopheline larvae are surface feeders and allocate most of their time to search for food at the water surface. However, species of the Anopheles gambiae Giles complex may also show bottom feeding. The consequences of this foraging tactic for life history are unknown, yet may be relevant to understand inter‐specific competition patterns. 2. The diving ability and activity of larvae of the main African malaria vectors, An. coluzzii and An. gambiae, at two different water depths (14 and 30 cm) were assessed. We further explored the biological relevance of diving for food harvesting by monitoring key life history traits in two species treatments (single or mixed species) and two food treatments (surface or bottom feeding). 3. Overall, An. coluzzii larvae showed more diving activity than An. gambiae. When feeding at the bottom both species, and especially An. gambiae, showed a delayed emergence and a reduced emergence rate. Moreover, An. gambiae also suffered a reduced wing length. 4. Mixed‐species rearing had a detrimental effect on the life history traits of An. gambiae but not on An. coluzzii, suggesting a competitive advantage for the latter in our experimental conditions. 5. The present results confirm that anopheline larvae are able to forage for food at the bottom of their breeding site and that An. coluzzii shows a superior diving activity than An. gambiae and this at a lower cost. These behavioural differences probably reflect specific adaptations to different aquatic habitats, and may be important in shaping species distributions and the population biology of these important vector mosquitoes.  相似文献   

3.
In Madagascar, Anopheles gambiae has been found below altitudes of 1,000 m. We sampled An. gambiae sensu lato (sl) between 2008 and 2010 in the Central Highlands of Madagascar at altitudes over 1,200 m. The study site consists of rainforest, rainforest edge, and an open savanna biotope. Anopheles gambiae and An. arabiensis, as well as molecular forms of An. gambiae, were identified molecularly. An. gambiae accounted for 26.7% at the edge of the rainforest and 2.3% in the open savanna biotope. One specimen of this species was caught in the forest. An. arabiensis accounted for 66.3% at the edge of the rainforest and 97.7 % in the open savanna biotope. All An. gambiae adults tested belonged to the S molecular form. An. gambiae is present at high altitudes in Madagascar, with a high prevalence at the rainforest edge. Several factors, including the appearance of new favorable biotopes, recolonization after a reduction of indoor vector control, and climate change, may contribute to its distribution. The changing distribution of An. gambiae may have consequences for the distribution and incidence of malaria in the Malagasy Highlands.  相似文献   

4.
The number of Anopheles gambiae and Anopheles arabiensis females that used each of the 33 sampled breeding sites in west Kenya was estimated by microsatellite markers and related statistics to test the hypothesis that conspecific females share aquatic sites. Totally, 166 An. gambiae and 168 An. arabiensis larvae were identified and were genotyped. The mean number of larvae per breeding site was 8.3 for An. gambiae and 8.4 for An. arabiensis. The likelihood method estimated that, for An. gambiae, the mean number of females that would have laid eggs per breeding site was 5.2 and ranged from 2 to 9, and for An. arabiensis, the mean was 5.0 with a range of 2–10. The clustering method estimated that the mean number of females laying eggs per breeding site was 6.8 for An. gambiae. The results provide molecular evidence that females of one or both species share breeding sites.  相似文献   

5.
Abstract. Identification of species within the Anopheles gambiae Giles species complex is essential for the correct evaluation of malaria vector ecology studies and control programmes. The development of DNA probes to distinguish species of the An.gambiae complex is described. Genomic libraries were prepared for four members of the An.gambiae complex. These were screened using radiolabeled DNA from different species of An. gambiae sensu lato and a number of clones selected on the basis of their species specificity. These clones could be divided into two groups, each containing homologous sequences. Sequences homologous to group 1 inserts are highly reiterated in the genomes of Anopheles arabiensis Patton and Anopheles merus Dönitz, present in low copy number in Anopheles melas Theobald, but were not detected in Anopheles gambiae sensu stricto. Studies on the organization of this sequence in the genome of An.arabiensis show that homologous sequences are male specific and interspersed within the chromatin. Sequences homologous to group 2 inserts are highly repeated in the genomes of An.merus and An.melas, but present in low copy number in An.gambiae s.s. and An.arabiensis. Group 2 homologous sequences are not sex-specific in the species tested and appear to be tandemly repeated. When used as hybridization probes, these sequences provide a sensitive means for the identification of species within the Anopheles gambiae complex.  相似文献   

6.

Background

Physical objects like vegetation can influence oviposition by mosquitoes on soil or water substrates. Anopheles gambiae s. l. is generally thought to utilize puddles over bare soil as its prime larval habitat and to avoid standing water populated with vegetation. In Kisian, Kenya near Kisumu, water often pools in grassy drainage areas both during and after periods of infrequent rains, when typical puddle habitats become scarce because of drying. This raised the question of whether An. gambiae has the behavioural flexibility to switch ovipositional sites when puddles over bare soil are unavailable.

Methods

To test whether presence and height of grasses influenced oviposition, wild-caught gravid An. gambiae s. l. were offered paired choices between wet, bare soil and wet soil populated with mixed grasses or grasses of differing height. No-choice tests were also conducted by giving females either grassy soil or bare soil.

Results

In choice tests, females laid four times more eggs on bare, wet soil than soil populated with grasses. However in no-choice tests, egg output was not significantly different whether grasses were present or not. Females laid significantly more eggs on soil populated with short grass than with medium, or tall grass.

Conclusion

This work shows An. gambiae s. l. has the capacity to oviposit into grassy aquatic habitats when typical puddles over bare soil are unavailable. This knowledge will need to be considered in the design and implementation of programmes aimed at reducing malaria transmission by suppression of An. gambiae s. l. immatures.
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7.
  1. Predation is a major evolutionary force driving speciation. Identifying the stimuli prompting anti‐predator responses is essential for unravelling the proximate mechanisms of anti‐predator adaptations and for understanding how predation impacts species diversification.
  2. Here, we explore for the first time the divergence in the use of cues of predation risk by different incipient species of mosquitoes within the Anopheles gambiae complex. We examined the anti‐predator responses to various predation cues by the aquatic larvae of Anopheles arabiensis and the two molecular forms, M and S, of Anopheles gambiae s.s. sampled from wild populations in Burkina Faso naturally exposed to different predator densities.
  3. The larvae altered their behaviour in response to various predation cues, shifting from the surface of the water to a less exposed location on the walls of the experimental arena. There were important differences in the use of predation cues between populations sharing the same larval development sites and, within the M form, related to predation pressure at their site of origin. Anopheles arabiensis larvae, which develop in small temporary waterbodies, relied only on physical cues signalling the presence of a predator to mount a vigilance response, whereas the sympatric larvae of the M and S forms of An. gambiae used both physical and chemical cues to fine‐tune their response. M‐form larvae, developing in permanent aquatic habitats with high densities of predators, responded chiefly to chemical stimuli ensuing from acute predation.
  4. Our results suggest that predation might play a role as a disruptive selective force promoting ecological divergence within the An. gambiae complex and, more recently, between the M and S molecular forms. Notably, beyond interspecific differences in the use of predation cues, our study also documented phenotypic differences within the M form based on predation pressure at their site of origin, suggesting that a process of ecological divergence is generating species ‘forerunners’ within the An. gambiae complex in the wild.
  相似文献   

8.
New genetic control methods for mosquitoes may reduce vector species without direct effects on other species or the physical environment common with insecticides or drainage. Effects on predators and competitors could, however, be a concern as Anopheles gambiae s.l. is preyed upon in all life stages. We overview the literature and assess the strength of the ecological interactions identified. Most predators identified consume many other insect species and there is no evidence that any species preys exclusively on any anopheline mosquito. There is one predatory species with a specialisation on blood‐fed mosquitoes including An. gambiae s.l.. Evarcha culicivora is a jumping spider, known as the vampire spider, found around Lake Victoria. There is no evidence that these salticids require Anopheles mosquitoes and will readily consume blood‐fed Culex. Interspecific competition studies focus on other mosquitoes of larval habitats. Many of these take place in artificial cosms and give contrasting results to semi‐field studies. This may limit their extrapolation regarding the potential impact of reduced An. gambiae numbers. Previous mosquito control interventions are informative and identify competitive release and niche opportunism; so while the identity and relative abundance of the species present may change, the biomass available to predators may not.  相似文献   

9.
Algae are important food resources of the larvae of the African malaria vectors, Anopheles gambiae Giles and Anopheles arabiensis Patton (Anopheles gambiae sensu lato), and other zooplankton, but empirical evidence remains meager about the agal flora in ephemeral water bodies. The animals present in natural aquatic habitats in western Kenya were sampled from July to November 2002 to study abiotic and biotic environmental factors determining A. gambiae sl larval abundance. The five highest concentrations of third and fourth instars and pupae (hereafter referred to as old-stage larvae) were sampled in conjunction with the unicellular epizoic green algae, Rhopalosolen species (Chlorophyta; Chlorophyceae). Canonical correspondence analysis revealed that the presence of Rhopalosolen species was the most important determinant of the animal assemblage. The density of old-stage A. gambiae sl larvae was positively correlated with the presence of Rhopalosolen species, but the density of first and second instars of A. gambiae sl was not. The water bodies with Rhopalosolen sp. yielded larger mosquitoes in spite of the higher density of larvae. We demonstrated that the productivity of water bodies in terms of the larvae of malaria vectors can differ in magnitude depending on the agal flora. We discuss phytoplankton as a regulator of mosquito larval populations.  相似文献   

10.
The flight behavior of Anopheles gambiae s.s. Giles and An. stephensi Patton exposed to different odor cues was studied in a wind tunnel. Odors consisted of CO2, CO2 + acetone (at two concentrations), and CO2 + 1-octen-3-ol. Mosquitoes were released singly and their behavior was recorded on video. Parameters studied included flight velocity, percentage of time spent flying, percentage of time spent in plume, and number of turns toward the plume. Large differences in behavior toward the odors tested were observed. An. gambiaedid not respond well to CO 2,whereas An. stephansiwas positively affected by this compound. In contrast, An. gambiaeresponded significantly to CO 2 + acetone (at a low concentration), but the behavior of An. stephensiwas completely suppressed by this combination of odor stimuli. CO 2 + a high concentration of acetone or CO 2 + 1-octen-3-ol did not cause significant effects in An. gambiaecompared to no odor, while these treatments elicited strong behavioral responses in An. stephensi.The latter species responded particularly well to CO 2 + 1-octen-3-ol. The results suggest that the observed differences may be inherent to the known differences in host preferences, where An. gambiaeis highly anthropophilic and An. stephensimore zoophilic. This would explain why the latter species responds well to CO 2 and even better to CO 2 + 1-octen-3-ol, a compound readily emitted by bovine ruminants.  相似文献   

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