Patrick M Guerin

Université de Neuchâtel, Neuenburg, Neuchâtel, Switzerland

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Publications (72)163.63 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A membrane feeding assay in which the effects of the antimalarial drugs quinine and artesunate are tested on Anopheles gambiae Giles sensu stricto is described. In the present study, 87% of female A. gambiae are shown to feed on whole defibrinated bovine blood alone, whereas only 47% and 43.5% feed on saline and on saline + bovine serum albumin (BSA) solutions, respectively, suggesting that additional components in the blood stimulate mosquito feeding. The addition of 1 mm quinine or artesunate to the BSA solution results in a significant reduction in percentage engorgement to 16.2% and 14.1%, respectively. However, the feeding rate is higher when 1 mm artesunate and quinine are mixed in the blood because 67.8% and 78.4% of females engorge on these solutions respectively. Artesunate (10 mm) in the blood reduces percentage engorgement to 20%. Because circulating doses of quinine and artesunate affecting Plasmodium in humans are much lower than those affecting feeding by A. gambiae in the in vitro assay, these two antimalarial drugs should have no effect, or only a minor effect, on the infection rate of mosquitoes feeding on treated patients. Because only the stylets penetrate the membrane and not the labellar lobes, the results of the present study suggest that both blood phagostimulants and feeding deterrents are detected by internal gustatory organs in A. gambiae, namely sensory cells in the apical and subapical labral pegs, in sensilla on the inner face of the labellar lobes, or by cibarial receptor cells. The neuroanatomy of gustatory sensilla on the apical and subapical labral pegs and on the inner face of the labellar lobes of female A. gambiae is described in the present study.
    Physiological Entomology 03/2014; · 1.42 Impact Factor
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    ABSTRACT: Glossina palpalis palpalis (G. p. palpalis) is one of the principal vectors of sleeping sickness and nagana in Africa with a geographical range stretching from Liberia in West Africa to Angola in Central Africa. It inhabits tropical rain forest but has also adapted to urban settlements. We set out to standardize a long-lasting, practical and cost-effective visually attractive device that would induce the strongest landing response by G. p. palpalis for future use as an insecticide-impregnated tool in area-wide population suppression of this fly across its range. Trials were conducted in wet and dry seasons in the Ivory Coast, Cameroon, the Democratic Republic of Congo and Angola to measure the performance of traps (biconical, monoconical and pyramidal) and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a practical enumerator at these remote locations to compare landing efficiencies of devices. Independent of season and country, both phthalogen blue-black and blue-black-blue 1 m(2) targets covered with adhesive film proved to be as good as traps in phthalogen blue or turquoise blue for capturing G. p. palpalis. Trap efficiency varied (8-51%). There was no difference between the performance of blue-black and blue-black-blue 1 m(2) targets. Baiting with chemicals augmented the overall performance of targets relative to traps. Landings on smaller phthalogen blue-black 0.25 m(2) square targets were not significantly different from either 1 m(2) blue-black-blue or blue-black square targets. Three times more flies were captured per unit area on the smaller device. Blue-black 0.25 m(2) cloth targets show promise as simple cost effective devices for management of G. p. palpalis as they can be used for both control when impregnated with insecticide and for population sampling when covered with adhesive film.
    PLoS Neglected Tropical Diseases 01/2014; 8(1):e2601. · 4.57 Impact Factor
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    ABSTRACT: Tsetse flies are obligatory blood feeders, accessing capillaries by piercing the skin of their hosts with the haustellum to suck blood. However, this behaviour presents a considerable risk as landing flies are exposed to predators as well as the host's own defense reactions such as tail flicking. Achieving a successful blood meal within the shortest time span is therefore at a premium in tsetse, so feeding until replete normally lasts less than a minute. Biting in blood sucking insects is a multi-sensory response involving a range of physical and chemical stimuli. Here we investigated the role of heat and humidity emitted from host skin on the biting responses of Glossina pallidipes, which to our knowledge has not been fully studied in tsetse before. The onset and duration of the biting response of G. pallidipes was recorded by filming movements of its haustellum in response to rapid increases in temperature and/or relative humidity (RH) following exposure of the fly to two airflows. The electrophysiological responses of hygroreceptor cells in wall-pore sensilla on the palps of G. pallidipes to drops in RH were recorded using tungsten electrodes and the ultra-structure of these sensory cells was studied by scanning and transmission electron microscopy. Both latency and proportion of tsetse biting are closely correlated to relative humidity (RH) when accompanied by an increase of 13.1[degree sign]C above ambient temperature but not for an increase of just 0.2[degree sign]C. Biting persistence, as measured by the number of bites and the time spent biting, also increases with increasing RH accompanied by a 13.1[degree sign]C increase in air temperature. Neurones in wall-pore sensilla on the palps respond to shifts in RH. Our results show that temperature acts synergistically with humidity to increase the rapidity and frequency of the biting response in tsetse above the levels induced by increasing temperature or humidity separately. Palp sensilla housing hygroreceptor cells, described here for the first time in tsetse, are involved in the perception of differences in RH.
    Parasites & Vectors 08/2013; 6(1):240. · 3.25 Impact Factor
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    ABSTRACT: Here we set out to standardize long-lasting, visually-attractive devices for , a vector of both human and animal trypanosomiasis in open savannah in Tanzania and Kenya, and in neighbouring conservation areas used by pastoralists. The goal was to determine the most practical device/material that would induce the strongest landing response in for use in area-wide population suppression of this fly with insecticide-impregnated devices. Trials were conducted in wet and dry seasons in the Serengeti and Maasai Mara to measure the performance of traps and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a simple enumerator at these remote locations to compare trapping efficiencies of devices. Independent of season or presence of chemical baits, targets in phthalogen blue or turquoise blue cloth with adhesive film were the best devices for capturing G. in all situations, catching up to 19 times more flies than pyramidal traps. Baiting with chemicals did not affect the relative performance of devices. Fly landings were two times higher on 1 m blue-black targets as on pyramidal traps when equivalent areas of both were covered with adhesive film. Landings on 1 m blue-black targets were compared to those on smaller phthalogen blue 0.5 m all-blue or blue-black-blue cloth targets, and to landings on all-blue plastic 0.32-0.47 m leg panels painted in phthalogen blue. These smaller targets and leg panels captured equivalent numbers of per unit area as bigger targets. Leg panels and 0.5 m cloth targets show promise as cost effective devices for management of as they can be used for both control (insecticide-impregnated cloth) and for sampling (rigid plastic with insect glue or adhesive film) of populations.
    PLoS Neglected Tropical Diseases 02/2013; 7(2):e2063. · 4.57 Impact Factor
  • T. Kröber, M. Bourquin, P.M. Guerin
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    ABSTRACT: The threat of transmission of Lyme borelliosis and tick-borne encephalitis by ixodid ticks has resulted in an increasing number of tick repellents coming onto the market. To allow proper evaluation of the efficacy of different types of compounds and their formulations, there is a need for standardised methods for testing ticks repellents. Ticks show a marked negative geotactic response following contact with a potential host, i.e., they climb up in order to locate attachment and feeding sites, whereas exposing ticks to repellents induces positive geotaxis, i.e., ticks walk downwards or drop off the treated host or substrate. We describe here complementary tests that employ these geotactic responses to evaluate repellents: one in vitro on a warm glass plate and the other on the lower human leg (shin). The compounds tested were DEET, EBAAP, icaridin, capric acid, lauric acid, geraniol, citriodiol, citronella essential oil and lavender essential oil, all non-proprietary ingredients of widely distributed tick repellent formulations.In controls on both the warm glass plate and the human leg, the majority of Ixodes ricinus nymphs walk upwards. By contrast, in both the in vitro and in vivo tests, effective doses of repellents cause ticks to either walk downwards or fall off the substrates, termed here “affected ticks”. The ED75 values for affected ticks on the human leg indicate that the test products can be divided into three groups: (1) icaridin, EBAAP, DEET and capric acid with values between 0.013 and 0.020 mg/cm2, (2) citriodiol and lauric acid with values between 0.035 and 0.058 mg/cm2, and (3) geraniol, citronella oil and lavender essential oil with values between 0.131 and 1.58 mg/cm2. The latter three products can be considered as less effective repellents. The tests on the warm glass plate resulted in very similar efficacy rankings for the products tested in vivo, and the ticks’ behavioural responses also corresponded closely to those observed on the treated human leg. The ED75 values on the glass plate ranged from half to one sixth needed on the leg. The warm glass plate test thus provides a reliable alternative to human subjects for an initial evaluation of new repellents, and is particularly appropriate for testing products with still to be determined human toxicity and dermatological effects.
    Pesticide Biochemistry and Physiology 01/2013; 107(2):160–168. · 2.11 Impact Factor
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    ABSTRACT: In this study, we show that female African malaria mosquitoes Anopheles gambiae (Giles) starved for 3-5 hours start to engorge on sucrose at concentrations between 50 to 75 mM. Half of the feeding response (ED50) is reached at 111 mM and the maximum response (0.4 mg) occurs from 146 mM (5% m/v). Two receptor cells in a trichoid sensillum of the labellum, called the 'sucrose' and the 'water' neurones, are activated by sucrose and water, respectively. The electrophysiological response of the sucrose receptor cell starts well below the level of sugar necessary to induce feeding. An. gambiae is most sensitive to small increments in sucrose concentration up to 10 mM with a response plateau at a maximum frequency of 53 spikes per 2 s from 50 mM, the concentration at which female An. gambiae start to engorge on sucrose. Fructose has a mild phagostimulatory effect on An. gambiae, whereas no significant differences in meal sizes between water and glucose were found. However, when 146 mM fructose plus glucose are mixed, the same engorgement as on 146 mM sucrose is observed. Likewise, even though the sucrose receptor cell is not activated by either fructose or glucose alone, equimolar solutions of fructose plus glucose activate the neurone. We conclude that there is a behavioural and a neurophysiological synergism between fructose and glucose, the two hexose sugars of sucrose. We show that bitter tasting products for humans have a deterrent effect on feeding in An. gambiae. When 1 mM quinidine, quinine or denatonium benzoate is added to 146 mM sucrose, feeding is almost totally inhibited. The effect of berberine is lower and no significant inhibition on engorgement occurs for caffeine. The deterrent effect depends on concentration for both quinine and quinidine. Capillary feeding experiments show that contact chemosensilla on the mouthparts are sufficient for the detection of sucrose and bitter products. The feeding assay findings with deterrents correlate with the neurophysiological responses of the sucrose and the water labellar neurones which are both inhibited by the bitter compounds denatonium benzoate, quinine and berberine between 0.01 and 1 mM, but not by the same concentrations of caffeine which has no effect on feeding. In conclusion, sucrose which stimulates feeding activates the labellar sucrose neurone whereas feeding deterrents inhibit both the sucrose and the water neurones. This study provides an initial understanding of the physiological mechanisms involved in sugar feeding in An. gambiae and shows how some bitter products interfere with it.
    Journal of Experimental Biology 12/2012; · 3.24 Impact Factor
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    ABSTRACT: Recording and analysing three dimensional (3D) motions of tsetse flies in flight are technically challenging due to their speed of flight. However, video recording of tsetse fly flight responses has already been made in both wind tunnels and the field. The aim of our research was to study the way tsetse flies exploit host odours and visual targets during host searching. Such knowledge can help in the development of better trapping devices. We built a wind tunnel where it is possible to control environmental parameters, e.g. temperature, relative humidity and light. The flight of the flies was filmed from above with two high speed Linux-embedded cameras equipped with fish-eye objectives viewing at 60o from one another. The synchronized stereo images were used to reconstruct the trajectory of flies in 3D and in real time. Software permitted adjustment for parameters such as luminosity and size of the tsetse species being tracked. Interpolation permitted us to calculate flight coordinates and to measure modifications of flight parameters such as acceleration, velocity, rectitude, angular velocity and curvature according to the experimental conditions. Using this system we filmed the responses of Glossina brevipalpis Newstead obtained from a colony at the IAEA Entomology Unit, Seibersdorf, Austria to human breath presented with and without a visual target. Flights lasting up to 150 s duration and covering up to 153 m were recorded. G. brevipalpis flights to human breath were characterized by wide undulations along the course. When a visual target was placed in the plume of breath, flights of G. brevipalpis were more tightly controlled, i.e. slower and more directed. This showed that after multiple generations in a laboratory colony G. brevipalpis was still capable of complex behaviours during bloodmeal searching.
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    PLoS Neglected Tropical Diseases 02/2012; 6(2). · 4.57 Impact Factor
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    ABSTRACT: Plant volatiles play an important role in the lives of phytophagous insects, by guiding them to oviposition, feeding and mating sites. We tested the effects of different host-plant volatiles on attraction of Lobesia botrana males to the female-produced sex pheromone, in a wind tunnel. Addition of volatile emissions from grapevines or individual plant volatiles to pheromone increased the behavioral responses of L. botrana males over those to pheromone alone. At a low release rate (under-dosed) of pheromone, addition of (E)-β-caryophyllene, (Z)-3-hexenyl acetate, 1-hexanol, or 1-octen-3-ol increased all behavioral responses, from activation to pheromone source contact, while addition of (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-β-farnesene, (Z)-3-hexenol, or methyl salicylate affected only the initial behavioral responses. Dose-response experiments suggested an optimal release ratio of 1:1000 (sex pheromone: host plant volatile). Our results highlight the role of plant volatiles in the sensory ecology of L. botrana.
    Journal of Chemical Ecology 02/2012; 38(2):222-5. · 2.46 Impact Factor
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    ABSTRACT: Mating disruption by sex pheromones is a sustainable, effective and widely used pest management scheme. A drawback of this technique is its challenging assessment of effectiveness in the field (e.g., spatial scale, pest density). The aim of this work was to facilitate the evaluation of field-deployed pheromone dispensers. We tested the suitability of small insect field cages for a pre-evaluation of the impact of sex pheromones on mating using the grape moths Eupoecilia ambiguella and Lobesia botrana, two major pests in vineyards. Cages consisted of a cubic metal frame of 35 cm sides, which was covered with a mosquito net of 1500 μm mesh size. Cages were installed in the centre of pheromone-treated and untreated vineyards. In several trials, 1 to 20 couples of grape moths per cage were released for one to three nights. The proportion of mated females was between 15 to 70% lower in pheromone-treated compared to untreated vineyards. Overall, the exposure of eight couples for one night was adequate for comparing different control schemes. Small cages may therefore provide a fast and cheap method to compare the effectiveness of pheromone dispensers under standardised semi-field conditions and may help predict the value of setting-up large-scale field trials.
    The Scientific World Journal 01/2012; 2012:960468. · 1.73 Impact Factor
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    ABSTRACT: The European grapevine moth Lobesia botrana relies on a female produced sex pheromone for long-distance mate finding. Grapevine moth males compete heavily during limited time windows for females. The aim of this study was to investigate the perception of host plant volatiles by grapevine moth males and whether such compounds elicit upwind oriented flights. We compared five host plant headspace extracts by means of gas chromatography linked electroantennogram (EAG) recording. We identified 12 common host plant volatiles (aliphatic esters, aldehydes, and alcohols, aromatic compounds and terpenes) that elicit EAG responses from grapevine moth males and that occur in at least three of the host plant volatile headspace extracts tested. Subsequently the behavioural response of grapevine moth males to four these compounds presented singly and in mixtures (1-hexanol, 1-octen-3-ol, (Z)-3-hexenyl acetate and (E)-β-caryophyllene) was recorded in a wind tunnel. Grapevine moth males engaged in upwind flights to all of four compounds when released singly at 10,000 pg/min and to all, except 1-octen-3-ol, when released at 100 pg/min. A blend of the four host plant volatiles released at 10,000 pg/min and mixed at a ratio based on the analysis of Vitis vinifera cv. Solaris volatile emissions attracted significantly more males than any single compound. Grapevine moth males perceive and respond to host plant volatiles at biologically relevant levels indicating that host plant volatiles figure as olfactory cues and that L. botrana males can discern places where the likelihood of encountering females is higher.
    Journal of insect physiology 06/2011; 57(10):1323-31. · 2.24 Impact Factor
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    ABSTRACT: Olfaction is of major importance for survival and reproduction in moths. Males possess highly specific and sensitive olfactory receptor neurones to detect female sex pheromones. However, the capacity of male moths to respond to host-plant volatiles is relatively neglected and the role that such responses could play in the sensory ecology of moths is still not fully understood. The present study aims to identify host-plant stimuli for the European grape berry moth Eupoecilia ambiguella Hb. (Tortricidae, Lepidoptera), a major pest of vine in Europe. Headspace volatiles from Vitis vinifera L. cv. Pinot Noir, Vitis vinifera subsp. sylvestris and five other host-plant species comprising five different families are analyzed by gas chromatography linked to electroantennogram (EAG) recording from male E. ambiguella antennae and by gas chromatography-mass spectrometry. This procedure identifies 32 EAG-active compounds, among them the aliphatic compounds 1-hexanol, (Z)-3-hexenol, (Z)-3-hexenyl acetate and 1-octen-3-ol; the terpenes limonene, β-caryophyllene and (E)-4,8-dimethyl-1,3,7-nonatriene; and the aromatic compounds benzaldehyde and methyl salicylate. Male and female E. ambiguella show similar EAG response amplitudes to individual chemical stimuli and also to mixtures of plant volatiles, as represented by essential oils from ten other plant species. This possibly indicates a common role for plant compounds in the sensory ecology of the two sexes of E. ambiguella.
    Physiological Entomology 06/2011; 36(2):101-110. · 1.42 Impact Factor
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    ABSTRACT: Differences in floral traits, such as petal color, scent, morphology, or nectar quality and quantity, can lead to specific interactions with pollinators and may thereby cause reproductive isolation. Petunia provides an attractive model system to study the role of floral characters in reproductive isolation and speciation. The night-active hawkmoth pollinator Manduca sexta relies on olfactory cues provided by Petunia axillaris. In contrast, Petunia exserta, which displays a typical hummingbird pollination syndrome, is devoid of scent. The two species can easily be crossed in the laboratory, which makes it possible to study the genetic basis of the evolution of scent production and the importance of scent for pollinator behavior. In an F2 population derived from an interspecific cross between P. axillaris and P. exserta, we identified two quantitative trait loci (QTL) that define the difference between the two species' ability to produce benzenoid volatiles. One of these loci was identified as the MYB transcription factor ODORANT1. Reciprocal introgressions of scent QTL were used for choice experiments under controlled conditions. These experiments demonstrated that the hawkmoth M. sexta prefers scented plants and that scent determines choice at a short distance. When exposed to conflicting cues of color versus scent, the insects display no preference, indicating that color and scent are equivalent cues. Our results show that scent is an important flower trait that defines plant-pollinator interactions at the level of individual plants. The genetic basis underlying such a major phenotypic difference appears to be relatively simple and may enable rapid loss or gain of scent through hybridization.
    Current biology: CB 05/2011; 21(9):730-9. · 10.99 Impact Factor
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    ABSTRACT: One of the most fascinating examples of parasite-induced host manipulation is that of hairworms, first, because they induce a spectacular "suicide" water-seeking behavior in their terrestrial insect hosts and, second, because the emergence of the parasite is not lethal per se for the host that can live several months following parasite release. The mechanisms hairworms use to increase the encounter rate between their host and water remain, however, poorly understood. Considering the selective landscape in which nematomorph manipulation has evolved as well as previously obtained proteomics data, we predicted that crickets harboring mature hairworms would display a modified behavioral response to light. Since following parasite emergence in water, the cricket host and parasitic worm do not interact physiologically anymore, we also predicted that the host would recover from the modified behaviors. We examined the effect of hairworm infection on different behavioral responses of the host when stimulated by light to record responses from uninfected, infected, and ex-infected crickets. We showed that hairworm infection fundamentally modifies cricket behavior by inducing directed responses to light, a condition from which they mostly recover once the parasite is released. This study supports the idea that host manipulation by parasites is subtle, complex, and multidimensional.
    Behavioral Ecology 01/2011; 22(2):392-400. · 3.22 Impact Factor
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    ABSTRACT: We describe here an in vitro behavioral assay for testing mosquito repellents applied in a dose-based manner to a warm body (34 degrees C) in test cages. The system was used to assess the sensitivity of 4-6-day-old Anopheles gambiae to the insect repellent diethyl methyl benzamide (deet). These tests were made in the absence and presence of additional carbon dioxide (CO2) applied as a pulse to activate mosquitoes in the cages. In the absence of the CO2 pulse the mosquitoes hardly responded to the warm body. Increasing the CO2 level in the cage by 1,000 parts per million caused a 25-fold increase in the number of landings by mosquitoes on the warm body in 2-min tests. This mosquito activation allowed the measurement of a significant reduction in the number of landings to bite on the warm body with increasing doses of deet (0.4 to 3.8 microg/cm2). An asymptotic nonlinear model fitted to the repellency data in the presence of CO2 allowed estimation of the effective dose of deet that reduced landings to bite by 50% (ED50) at 0.95 microg/cm2 (5 nmol/cm2) and the corresponding ED95 at 4.12 microg/cm2 (21.5 nmol/cm2). This in vitro bioassay has the advantage of permitting a fast throughput of test products under standardized conditions and is suitable for screenings designed for the purpose of discovering lead products with as yet unknown human toxicological and dermatological profiles.
    Journal of the American Mosquito Control Association 12/2010; 26(4):381-6. · 0.76 Impact Factor
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    ABSTRACT: Haematophagous insects are frequently carriers of parasitic diseases, including malaria. The mosquito Anopheles gambiae is the major vector of malaria in sub-Saharan Africa and is thus responsible for thousands of deaths daily. Although the role of olfaction in A. gambiae host detection has been demonstrated, little is known about the combinations of ligands and odorant binding proteins (OBPs) that can produce specific odor-related responses in vivo. We identified a ligand, indole, for an A. gambiae odorant binding protein, AgamOBP1, modeled the interaction in silico and confirmed the interaction using biochemical assays. RNAi-mediated gene silencing coupled with electrophysiological analyses confirmed that AgamOBP1 binds indole in A. gambiae and that the antennal receptor cells do not respond to indole in the absence of AgamOBP1. This case represents the first documented instance of a specific A. gambiae OBP-ligand pairing combination, demonstrates the significance of OBPs in odor recognition, and can be expanded to the identification of other ligands for OBPs of Anopheles and other medically important insects.
    PLoS ONE 01/2010; 5(3):e9471. · 3.73 Impact Factor
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    Vincent Harraca, Z Syed, P M Guerin
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    ABSTRACT: Herbivores provide tsetse flies with a blood meal, and both wild and domesticated ruminants dominate as hosts. As volatile metabolites from the rumen are regularly eructed with rumen gas, these products could serve tsetse flies during host searching. To test this, we first established that the odour of rumen fluid is attractive to hungry Glossina pallidipes in a wind tunnel. We then made antennogram recordings from three tsetse species (G. pallidipes morsitans group, G. fuscipes palpalis group and G. brevipalpis fusca group) coupled to gas chromatographic analysis of rumen fluid odour and of its acidic, mildly acidic and neutral fractions. This shows tsetse flies can detect terpenes, ketones, carboxylic acids, aliphatic aldehydes, sulphides, phenols and indoles from this biological substrate. A mixture of carboxylic acids at a ratio similar to that present in rumen fluid induced behavioural responses from G. pallidipes in the wind tunnel that were moderately better than the solvent control. The similarities in the sensory responses of the tsetse fly species to metabolites from ruminants demonstrated in this study testify to a contribution of habitat exploitation by these vertebrates in the Africa-wide distribution of tsetse.
    Journal of Comparative Physiology 08/2009; 195(9):815-24. · 1.86 Impact Factor
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    ABSTRACT: The European grape berry moth is an important pest in vineyards. Males respond to the female-produced sex pheromone released from a piezo nebulizer in a dose-dependent manner in a wind tunnel: <50% arrive at the source at 5-50 pg/min (underdosed), 80% arrive at 100 pg/min to 10 ng/min (optimal) and <20% arrive at 100 ng/min (overdosed). Males responding to overdosed pheromone show in flight arrestment at 80 cm from the source. Host plant chemostimuli for Eupoecilia ambiguella increase the responses of males to underdosed and overdosed pheromone. (Z)-3-hexen-1-ol, (+)-terpinen-4-ol, (E)-beta-caryophyllene and methyl salicylate released with the underdosed pheromone cause a significant increase in male E. ambiguella flying to the source. Time-event analysis indicates a positive correlation between faster activation and probability of source contact by the responding males. The four host plant compounds added to the overdosed pheromone permitted males to take off faster and with a higher probability of flying to the source. This suggests that perception of host plant products with the sex pheromone facilitates male E. ambiguella to locate females on host plants, lending credence to the hypothesis that plant products can signal rendezvous sites suitable for mating.
    Journal of Comparative Physiology 08/2009; 195(9):853-64. · 1.86 Impact Factor
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    Paul G Becher, Patrick M Guerin
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    ABSTRACT: Larvae of the grapevine moth Lobesia botrana (Lepidoptera: Tortricidae) are a major pest of vine, Vitis vinifera. As larvae have limited energy reserves and are in danger of desiccation and predation an efficient response to plant volatiles that would guide them to food and shelter could be expected. The responses of starved 2nd or 3rd instar larvae to volatile emissions from their artificial diet and to single host plant volatiles were recorded on a locomotion compensator. Test products were added to an air stream passing over the 30cm diameter servosphere. The larvae showed non-directed walks of low rectitude in the air stream alone but changed to goal-oriented upwind displacement characterised by relatively straight tracks when the odour of the artificial diet and vapours of methyl salicylate, 1-hexanol, (Z)-3-hexen-1-ol, terpinen-4-ol, 1-octen-3-ol, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenyl acetate were added to the air stream. This chemoanemotactic targeted displacement illustrates appetence for certain volatile cues from food by starved Lobesia larvae. Analysis of the larval behaviour indicates dose dependent responses to some of the host plant volatiles tested with a response to methyl salicylate already visible at 1ng, the lowest source dose tested. These behavioural responses show that Lobesia larvae can efficiently locate mixtures of volatile products released by food sources as well as single volatile constituents of their host plants. Such goal-oriented responses with shorter travel time and reduced energy loss are probably of importance for larval survival as it decreases the time they are exposed to biotic and abiotic hazards.
    Journal of insect physiology 02/2009; 55(4):384-93. · 2.24 Impact Factor
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    Dany Arsic, Patrick M Guerin
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    ABSTRACT: Regulation of female mosquito feeding and reproduction plays a central role in their disease-vector competence. In this study we show that Anopheles gambiae mosquitoes engorged on albumin, amino acid and saline meals the same way as on blood, whereas sucrose evoked a typical plant nectar feeding response. Among the artificial diets, only the albumin-containing ones allowed follicular development. The target of rapamycin (TOR)/p70 S6 kinase (S6K) pathway has been identified as an essential nutrient-sensing tool controlling egg development in mosquitoes under the control of regulating inputs from the insulin pathway. We assayed the early response of TOR, S6K, tuberous sclerosis (TSC2), insulin receptor (INR) and two insulin-like peptides (ILPs) by quantitative real-time PCR assessment of mRNA levels and immunoblotting of phosphorylated active TOR and S6K in An. gambiae ovary and brain 3 h after engorgement. We show that transcript levels of s6k and members of the insulin pathway are readily affected by nutrients (especially one ILP in the head) and that the TOR/S6K phosphorylation is able to react quickly to a meal to an extent which depends on the true nutritive value.
    Journal of Insect Physiology 08/2008; 54(8):1226-35. · 2.38 Impact Factor

Publication Stats

1k Citations
163.63 Total Impact Points

Institutions

  • 1992–2014
    • Université de Neuchâtel
      • • Faculté des sciences
      • • Laboratoire de physiologie végétale
      Neuenburg, Neuchâtel, Switzerland
  • 2012
    • Centre international de recherche-développement sur l'elevage en zone subhumide (CIRDES)
      Bobo-Diulasso, High-Basins Region, Burkina Faso