Novel use of stir bar sorptive extraction (SBSE) as a tool for isolation of oviposition site attractants for gravid Culex quinquefasciatus

Abstract

Mosquitoes such as Culex quinquefasciatus Say (Diptera: Culicidae) are important vectors of organisms that cause disease in humans. Research into the development of effective standardized odour baits for blood-fed females (oviposition attractants), to enable entomological monitoring of vector populations, is hampered by complex protocols for extraction of physiologically active volatile chemicals from natural breeding site water samples, which have produced inconsistent results. Air entrainment and solvent extraction are technically demanding methods and are impractical for use in resource poor environments where mosquito-borne disease is most prevalent. This study reports the first use of a simple, robust extraction technique, stir bar sorptive extraction (SBSE), to extract behaviourally active small lipophilic molecules (SLMs) present in water samples collected from Cx. quinquefasciatus breeding sites in Tanzania. Extracts from a pit latrine and from a cess pool breeding site attracted more gravid Cx. quinquefasciatus in pair choice bioassays than control extracts, and coupled gas chromatography-electroantennography (GC-EAG) allowed tentative identification of 15 electrophysiologically active chemicals, including the known oviposition attractant, skatole (3-methylindole). Here, we have demonstrated, using simple pair choice bioassays in controlled laboratory conditions, that SBSE is effective for the extraction of behaviourally and electrophysiologically active semiochemicals from mosquito breeding site waters. Further research is required to confirm that SBSE is an appropriate technique for use in field surveys in the search for oviposition cues for Cx. quinquefasciatus.

Effect of small lipophilic molecules in tomato and rice root exudates on the behaviour of Meloidogyne incognita and M. graminicola

“…Thus, we speculate that SLMs present in both tomato and rice root exudates might have allellopathic effects on these nematodes, that they might act as repellents when perceived from a certain distance, and that they have a nematostatic effect when in contact with the J2. Roles for SLMs as semiochemicals (behaviour-modifying chemicals) that influence the behaviour of invertebrate arthropods in other aqueous systems have also been discovered in our laboratory, e.g., mosquito oviposition cues (Carson et al, 2010), and host/non-hosts cues for Lepeophtheirus salmonis, an ectoparasite affecting salmonid fish (Mordue & Birkett, 2009). Furthermore, strigolactone and other lipophilic low molecular weight compounds exuded from plant roots act as host signals for beneficial fungal symbionts and parasitic weeds (Giovannetti et al, 1996;Nagahashi & Douds, 1999;Akiyama & Hayashi, 2006).…”

Olfactory basis of floral preference of the malaria vector Anopheles gambiae (Diptera: Culicidae) among common African plants

“…By this method the analytes are adsorbed on a thick film of polydimethylsiloxane (PDMS) (0.5 mm film thickness, 24‐µl volume) that coats a glass‐jacketed preconditioned Gerstel Twister® magnetic stir bar (Gerstel, Inc., Linthicum, MD, U.S.A.). SBSE is efficient at collecting trace amounts of compounds in static headspace and liquids (Baltussen et al ; Pfannkoch et al ; Scascighini et al ; David and Sandra ; Carson et al ). Each stir bar was suspended in the matrix headspace of cuttings consisting only of leaves and stems or only of floral tissue of P. hysterophorus, S. didymobotrya, L. camara , and S. occidentalis enclosed in nylon oven bags (26.7×20.3×14 cm) for 2 h during daytime.…”

An Invasive Whitefly Feeding on a Virus-Infected Plant Increased Its Egg Production and Realized Fecundity

“…Recent phylogenetic analysis combined with a pattern of reproductive isolation among genetic groups within B . tabaci indicates that the complex contains at least 24 cryptic species, some of which have been referred to as ‘biotypes’ in the last 20 years [14], [15]. As the separation at the species level within the B .…”

“…tabaci species complex [14], [15]. The notorious invasive B entered China in the late 1990s and now is the predominant or only biotype in many regions of the country [2], [26], [27].…”