Abstract
BackgroundMaize cultivation contributes to the prevalence of malaria mosquitoes and exacerbates malaria transmission in sub-Saharan Africa. The pollen from maize serves as an important larval food source for Anopheles mosquitoes, and females that are able to detect breeding sites where maize pollen is abundant may provide their offspring with selective advantages. Anopheles mosquitoes are hypothesized to locate, discriminate among, and select such sites using olfactory cues, and that synthetic volatile blends can mimic these olfactory-guided behaviours.MethodsTwo-port olfactometer and two-choice oviposition assays were used to assess the attraction and oviposition preference of gravid Anopheles arabiensis to the headspace of the pollen from two maize cultivars (BH-660 and ZM-521). Bioactive compounds were identified using combined gas chromatography and electroantennographic detection from the headspace of the cultivar found to be most attractive (BH-660). Synthetic blends of the volatile compounds were then assessed for attraction and oviposition preference of gravid An. arabiensis, as above.ResultsHere the collected headspace volatiles from the pollen of two maize cultivars was shown to differentially attract and stimulate oviposition in gravid An. arabiensis. Furthermore, a five-component synthetic maize pollen odour blend was identified, which elicited the full oviposition behavioural repertoire of the gravid mosquitoes.ConclusionsThe cues identified from maize pollen provide important substrates for the development of novel control measures that modulate gravid female behaviour. Such measures are irrespective of indoor or outdoor feeding and resting patterns, thus providing a much-needed addition to the arsenal of tools that currently target indoor biting mosquitoes.
Highlights
Maize cultivation contributes to the prevalence of malaria mosquitoes and exacerbates malaria transmission in sub-Saharan Africa
Maize pollen volatiles attract gravid mosquitoes Gravid An. arabiensis were significantly attracted, over a range of release rates, to the headspace collections of pollen collected from the ZM-521 and Bako Hybrid (BH)-660 maize varieties in a two-port olfactometer, when compared to the hexane control (ZM-521: χ2 = 9.647, P = 0.0019; BH-660: χ2 = 8.976, P = 0.0027; Fig. 1a, c; Additional file 1) and the headspace of breeding water (ZM-521: χ2 = 10.66, P = 0.0011; BH-660: χ2 = 16.77, P < 0.0001; Fig. 1b, d; Additional file 1)
No significant difference was observed in the attraction to the hexane control and the headspace of breeding water when tested in the same assay (χ2 = 0.5968, P = 0.4398)
Summary
Maize cultivation contributes to the prevalence of malaria mosquitoes and exacerbates malaria transmission in sub-Saharan Africa. The pollen from maize serves as an important larval food source for Anopheles mosquitoes, and females that are able to detect breeding sites where maize pollen is abundant may provide their offspring with selective advantages. In particular, serves as an important source of larval nourishment for Anopheles mosquitoes [14], which are adapted to breed in transient turbid water that can often be found associated with agricultural activities [9, 13]. Female mosquitoes that are able to detect breeding sites where maize pollen is abundant may provide their offspring with selective advantages, including survival and developmental [9, 13, 14]. Identifying and manipulating sensory cues that mediate a female mosquito’s ability to choose superior oviposition sites could provide important insights essential to developing novel mosquito control tools
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