Behavioural response of the malaria vector Anopheles gambiae to host plant volatiles and synthetic blends

Abstract

BackgroundSugar feeding is critical for survival of malaria vectors and, although discriminative plant feeding previously has been shown to occur in Anopheles gambiae s.s., little is known about the cues mediating attraction to these plants. In this study, we investigated the role of olfaction in An. gambiae discriminative feeding behaviour.MethodsDual choice olfactometer assays were used to study odour discrimination by An. gambiae to three suspected host plants: Parthenium hysterophorus (Asteraceae), Bidens pilosa (Asteraceae) and Ricinus communis (Euphorbiaceae). Sugar content of the three plant species was determined by analysis of their trimethylsilyl derivatives by coupled gas chromatography–mass spectrometry (GC-MS) and confirmed with authentic standards. Volatiles from intact plants of the three species were collected on Super Q and analyzed by coupled GC-electroantennographic detection (GC-EAD) and GC-MS to identify electrophysiologically-active components whose identities were also confirmed with authentic standards. Active compounds and blends were formulated using dose–response olfactory bioassays. Responses of females were converted into preference indices and analyzed by chi-square tests. The amounts of common behaviourally-active components released by the three host plants were compared with one-way ANOVA.ResultsOverall, the sugar contents were similar in the two Asteraceae plants, P. hysterophorus and B. pilosa, but richer in R. communis. Odours released by P. hysterophorus were the most attractive, with those from B. pilosa being the least attractive to females in the olfactometer assays. Six EAD-active components identified were consistently detected by the antennae of adult females. The amounts of common antennally-active components released varied with the host plant, with the highest amounts released by P. hysterophorus. In dose–response assays, single compounds and blends of these components were attractive to females but to varying levels, with one of the blends recording a significantly attractive response from females when compared to volatiles released by either the most preferred plant, P. hysterophorus (χ2 = 5.23, df = 1, P < 0.05) or as a synthetic blend mimicking that released by P. hysterophorus.ConclusionsOur results demonstrate that (a) a specific group of plant odours attract female An. gambiae (b) females use both qualitative and quantitative differences in volatile composition to associate and discriminate between different host plants, and (c) altering concentrations of individual EAD-active components in a blend provides a practical direction for developing effective plant-based lures for malaria vector management.

Sugar-sensitive neurone responses and sugar feeding preferences influence lifespan and biting behaviours of the Afrotropical malaria mosquito, Anopheles gambiae

“…By comparison, glucose and fructose alone and the other sugars tested represent weak stimuli. Our data indicate that labellar sugar-sensitive neurones are tuned to detect constituents of floral nectar-sucrose and mixtures of fructose and glucose-of plant species growing in the habitat of A. gambiae (Manda et al 2007a, b;Nyasembe et al 2012). Although melezitose is scarce in floral and extrafloral nectars, it is a constituent of homopteran honeydews (Heimpel and Jervis 2005) and provides an alternative potential source of energy for A. gambiae (Gary and Foster 2004).…”

“…5 sensilla were compared to stimulation with ecologically relevant sugars at 100 mM in 10 mM KCl. The sugars tested were sucrose, fructose, glucose, gulose and maltose which are found in nectars of Kenyan plant species preferred by A. gambiae (Manda et al 2007a;Nyasembe et al 2012) and melezitose, trehalose and turanose which are components of homopteran honeydew (Heimpel and Jervis 2005). For comparison, sorbose, a non-nutritive phagostimulant for the black salt marsh mosquito Aedes taeniorhynchus (Nayar and Sauerman 1971), and sorbitol, which is tasteless but nutritionally valuable for Drosophila (Burke and Waddell 2011;Fujita and Tanimura 2011), were also included.…”

“…Sugar is generally preferred over a blood meal by female A. gambiae 2-4 days following emergence, possibly to increase their lifespan (Stone et al 2011). Most plant nectars found in A. gambiae habitats contain sucrose and/or its hexose hydrolysis products glucose and fructose (Foster 1995;Manda et al 2007a, b;Nyasembe et al 2012) and typical sugar concentrations in floral nectar are between 20 and 1 3 50 % (Foster 1995). Nectar constituents known to influence both mosquito sugar-meal choices and longevity include carbohydrates Sauerman 1971, 1975;Andersson 1992;Ignell et al 2010;Kessler et al 2013), amino acids (Ignell et al 2010;Vrzal et al 2010) or potentially toxic secondary metabolites such as alkaloids (Ignell et al 2010;Kessler et al 2013).…”

Polyamidoamine Nanoparticles as Nanocarriers for the Drug Delivery to Malaria Parasite Stages in the Mosquito Vector

“…Suspected preferred host plants for Anopheles gambiae include Asteracaeae spp. and Ricinus communis [94]. Analysis of purified odorants from these plants has revealed enrichment of volatile compounds known as terpenes, including 10-carbon monoterpenes such as pinene and limonene, which at low concentrations have been shown to mediate attraction of Anopheles spp.…”

“…Analysis of purified odorants from these plants has revealed enrichment of volatile compounds known as terpenes, including 10-carbon monoterpenes such as pinene and limonene, which at low concentrations have been shown to mediate attraction of Anopheles spp. [94,95]. Several approaches are currently available for oral delivery to mosquitoes by droplet or liquid feeding, through dry diets [96], or via nylon strips continuously dispensing synthetic mosquito attractants for several weeks [97,98].…”