Host location by<i>Aedes aegypti</i>(Diptera: Culicidae): a wind tunnel study of chemical cues

Olfactory learning in blood-feeding insects, such as mosquitoes, could play an important role in host preference and disease transmission. However, standardised protocols allowing testing of their learning abilities are currently lacking, and how different olfactory stimuli are learned by these insects remains unknown. Using a Pavlovian conditioning paradigm, we trained individuals and groups of Aedes aegypti mosquitoes to associate an odorant conditioned stimulus (CS) with a blood-reinforced thermal stimulus (unconditioned stimulus; US). Results showed, first, that mosquitoes could learn the association between L-lactic acid and the US, and retained the association for at least 24 h. Second, the success of olfactory conditioning was dependent upon the CS -some odorants that elicited indifferent responses in naïve mosquitoes, such as L-lactic acid and 1-octen-3-ol, were readily learned, whereas others went from aversive to attractive after training (Z-3-hexen-1-ol) or were untrainable (β-myrcene and benzyl alcohol). Third, we examined whether mosquitoes' ability to learn could interfere with the action of the insect repellent DEET. Results demonstrated that pre-exposure and the presence of DEET in the CS reduced the aversive effects of DEET. Last, the nature of the formed memories was explored. Experiments using cold-shock treatments within the first 6 h posttraining (for testing anaesthesia-resistant memory) and a protein synthesis inhibitor (cycloheximide; to disrupt the formation of longterm memory) both affected mosquitoes' performances. Together, these results show that learning is a crucial component in odour responses in A. aegypti, and provide the first evidence for the functional role of different memory traces in these responses.

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“…This concentration is similar to that emitted by human skin (Eiras and Jepson, 1991;Cork and Park, 1996;Geier et al, 1996).…”

Section: Individual Trainingsupporting

confidence: 74%

Olfactory learning and memory in the disease vector mosquito,Aedes aegypti

Vinauger

Lutz

Riffell

2014

Journal of Experimental Biology

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“…This volatile is emitted by vertebrates and has been detected on human skin (Acree et al, 1968;Bernier et al, 2000). LA was demonstrated to be the major component of perspiration (Braks et al, 1999), excreted at concentrations between 0.5 and 5mgml -1 (Eiras and Jepson, 1991;Cork and Park, 1996;Geier et al, 1996). In triatomine bugs, it is behaviourally neutral when presented alone, but lowers the response threshold of the bugs to CO 2 and fatty acids when combined with them (Barrozo and Lazzari, 2004a;Barrozo and Lazzari, 2004b).…”

Section: Conditioning Proceduresmentioning

confidence: 99%

Learning the way to blood: first evidence of dual olfactory conditioning in a blood-sucking insect, Rhodnius prolixus. I. Appetitive learning

Vinauger

Buratti

Lazzari

2011

Journal of Experimental Biology

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a major role in host-seeking behaviour in haematophagous insects (Lazzari, 2009;Guerenstein and Lazzari, 2009 Accepted 28 June 2011 SUMMARY It has been largely assumed that the individual experience of insects that are disease vectors might not only contribute to animal fitness, but also have an important influence on parasite transmission. Nevertheless, despite the invested efforts in testing the capacity to learn and remember information in blood-sucking insects, only little conclusive information has been obtained to date. Adapting a classical conditioning approach to our haematophagous model, we trained larvae of Rhodnius prolixus to associate Llactic-acid, an odour perceived by these bugs but behaviourally neutral when presented alone, with food (i.e. positive reinforcement). Naive bugs -those exposed either to a conditioned stimulus (CS, L-lactic acid), unconditioned stimulus (US, heat) and reward (blood) alone or CS, US and reward in the absence of contingency -remained indifferent to the presence of an air stream loaded with L-lactic acid when tested in an olfactometer (random orientation), whereas the groups previously exposed to the contingency CS-US-reward (blood) were significantly attracted by L-lactic-acid. In a companion paper, the opposite, i.e. repellence, was induced in bugs exposed to the contingency of the same odour with a negative reinforcement. This constitutes the first evidence of olfactory conditioning in triatomine bugs, vectors of Chagas disease, and one of the few substantiations available to date of olfactory conditioning in haematophagous insects.

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“…Carbon dioxide (CO 2 ) is a known attractant for mosquitoes and fluctuations in the atmospheric concentration of the gas can indicate the presence of a host (Reeves 1990, Dekker et al 2005. CO 2 also activates the host-seeking behaviour of mosquitoes, including Aedes aegypti (L.) (Eiras & Jepson 1991). CO 2 -baited traps have been widely used to increase catch rates of mosquitoes, including for monitoring of Ae.…”

mentioning

confidence: 99%