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Guerin, Patrick
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Guerin, Patrick
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patrick.guerin@unine.ch
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- PublicationAccĆØs libreUltrastructure and receptor cell responses of the antennal grooved peg sensilla of Triatoma infestans (Hemiptera : Reduviidae)(2003)
; ; - PublicationAccĆØs libreDarkness induces mobility, and saturation deficit limits questing duration, in the tick Ixodes ricinus(2003)
; ; ; The behaviour of Ixodes ricinus nymphs was recorded in 10-day experiments using computer-assisted video-tracking, in the absence of any host stimuli. These ticks switch spontaneously from questing in a desiccating atmosphere to quiescence in a water-saturated atmosphere after dark. Quantification of both questing and quiescence duration demonstrates that questing duration is inversely related to saturation deficit whereas quiescence duration is not. Distance walked after quiescence increased with desiccating conditions, while the distance walked after questing remained unchanged. Almost all locomotor activities of I. ricinus occurred during darkness under either a 14 h:10 h L:D or a 8 h:4 h L:D cycle. We established that all life stages of I. ricinus are equipped to sense shifts in light intensity with bilaterally placed strings of photoreceptors. This permits I. ricinus to use onset of darkness to trigger mobility when desiccation risk is reduced in nature. - PublicationAccĆØs libreUltrastructure and receptor cell responses of the antennal grooved peg sensilla of Triatoma infestans (Hemiptera: Reduviidae)(2003)
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Electrophysiological recordings from the GP sensilla indicate that they house NH3, short-chain carboxylic acid and short-chain aliphatic amine receptor cells and can be divided into three functional sub-types (GP 1ā3). All GP sensilla carry a receptor cell excited by aliphatic amines, such as isobutylamine, a compound associated with vertebrate odour. GP type 1 and 2 sensilla house, in addition, an NH3-excited cell whereas the type 2 sensilla also contains a short-chain carboxylic acid receptor. No cell particularly sensitive to either NH3 or carboxylic acids was found in the grooved-peg type 3 sensilla. GP types 1, 2 and 3 represent ca. 36, 10 and 43% of the GP sensilla, respectively, whereas the remaining 11% contain receptor cells that manifest normal spontaneous activity but do not respond to any of the afore mentioned stimuli. - PublicationAccĆØs libreChemosensory and behavioural adaptations of ectoparasitic arthropods(2000)
; ; ; ; - PublicationAccĆØs libreChemsensory and Behavioural Adaptations of Ectoparasitic Arthropods(2000)
; ; ; - PublicationAccĆØs libreAliphatic alcohols and aldehydes of the honey bee cocoon induce arrestment behavior in Varroa jacobsoni (Acari: Mesostigmata), an ectoparasite of Apis mellifera(Wiley, 1998)
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Extracts of the European honey bee cocoons induce a strong arrestment response in the mite, as indicated by prolonged periods of walking on the extracts applied on a semipermeable membrane and by systematically returning to the stimulus after encountering the treatment borders. Two thin-layer chromatography fractions of the cocoon extract eliciting arrestment were found to contain saturated C17 to C22 primary aliphatic alcohols and C19 to C22 aldehydes.
We analyzed extracts of the cocoon and different larvae, pupae, and adults of both worker and drone A. mellifera to determine the relative amounts of these chemostimuli in the different substrates employed by Varroa. Both aldehydes and alcohols were more abundant in the cocoon than in the cuticle of adult or developing bees.
Mixtures of the aliphatic alcohols and aldehydes at the proportions found in the cocoons acted synergistically on the arrestment response, but this activity disappeared when mixed in equal amounts. When these oxygenated chemostimuli were mixed with C19 to C25 alkanes at the proportions found in the cocoon extract, we observed a significantly lower threshold for the chemostimulant mixture. These results indicate how Varroa may use mixtures of rarer products to differentiate between substrates and host stages during its developmental cycle within honey bee brood cells. - PublicationAccĆØs libreThe life-cycle of the bont tick Amblyomma hebraeum in vitro(1995)
; The life-cycle of the hard tick Amblyomma hebraeum was completed in vitro by feeding all life-stages of the tick through silicone membranes on bovine blood from an abattoir. Ticks were placed in a simple feeder consisting of a honey jar containing the blood with a glass tube insert (o.d. 42 mm) across the end of which the membrane was stretched. This feeding unit was held in a water bath (38Ā°C). Larvae and nymphs fed on a membrane (<90 Ī¼m thick) made of silicone reinforced with KodakĀ® lens cleaning paper, and adults on a silicone membrane (0.5 mm thick) reinforced with TeryleneĀ® netting. To control microbial growth, gentamicin (5 Ī¼g/ml) and nystatin (100 i.u./ml) were added to the weekly open-collected blood, which was manually defibrinated. The blood was changed twice daily for nymphs and three times for adults and larvae. Attachment of ticks was induced with combinations of host hair, tick faeces, a bovine pelage extract and a synthetic aggregation-attachment pheromone mixture. The in vitro life-cycle started with unengorged ānaturalā adults, which had moulted from nymphs fed on steer. The life-cycle closed with unengorged, first in vitro generation adults which had moulted from nymphs fed in vitro. Although the feeding and development of larvae and nymphs were similar to in vivo controls, females fed and developed poorly in vitro. The toxicity of the systemic acaricide IvermectinĀ® for nymphs of A. hebraeum was confirmed using the in vitro feeding method. - PublicationAccĆØs libreCuticle alkanes of honeybee larvae mediate arrestment of bee parasite Varroa jacobsoni(1994)
; The ectoparasitic mite Varroa jacobsoni invades worker brood cells of the honeybee Apis mellifera during the last 20 hr before the cells are sealed with a wax cap. Cuticle extracts of 8-day-old worker honeybee larvae occupying such brood cells have an arrestment effect on the mite. The mites run for prolonged periods on the extract, systematically returning onto the stimulus after touching the borders of the treated area. Mites increase walking speed and path straightness in response to increasing doses of a nonpolar fraction of the cuticle extract. Saturated straight-chain odd-numbered C19āC29 hydrocarbons were identified by thin-layer argentation chromatography and gas chromatography-mass spectrometry as the most active constituents, with branched alkanes also contributing to the arrestment effect of this active fraction. Analysis of the behavior responses to synthetic n-alkanes indicate that the response is probably based on a synergism between the different alkane components of the fraction rather than to an individual compound. - PublicationAccĆØs libreContrasting effects of sera from rabbit and cattle infested with ticks on the in vitro feeding performance of the tick Rhipicephalus appendiculatus(1993)
; The in vitro feeding activity of partially engorged Rhipicephalus appendiculatus (Neumann) (Acari: Ixodidae) females fed on sera from uninfested hosts was compared to that of ticks fed serum of hosts which had previously been infested with ticks. Although ticks fed best on sera from bovid hosts which had no prior exposure to this ectoparasite, two infestations of a bovid had no significant effect on the acceptability of its serum. In contrast, ticks fed sera from rabbits which had twice been infested with ticks gained significantly less weight than those fed serum obtained from the same animals before the infestation. Clearly there is a difference between natural host resistance and that of laboratory animals. - PublicationAccĆØs libreFeeding electrogram studies on the African cattle brown ear tick Rhipicephalus appendiculatus: evidence for an antifeeding effect of tick resistant serum(1992)
; Feeding behaviour of partially engorged Rhipicephalus appendiculatus (Neumann) (Acari: Ixodidae) on rabbit serum held in capillary tubes and placed over the tick mouthparts was studied using the feeding electrogram technique with simultaneous macro video photography. Correlation of electrical events with fluid movement in the vicinity of the tick's mouthparts and the capillary meniscus, permitted the characterization of an orderly sequence of signals, termed the āFeeding Complexā, associated with highest weight gains. This complex consisted of a 3ā8 Hz fast-sucking waveform typically lasting 4ā5 min, a sharp drop in potential at salivation, and rest lasting 1 or 2 min where no waveform or fluid movements occur. Very high impedence recordings from within the tick capitulum indicate that the fast-sucking waveform coincides with bursts of potentials corresponding to contraction of the pharyngeal dilator muscles, whereas during rest a tonic series of spikes signifies that the floor of the salivarium is actively lowered. Feeding electrograms of ticks fed on serum from tick-resistant rabbits showed significantly fewer feeding complexes. The weight gains achieved by these ticks were reduced correspondingly. This suggests that some of the humoral effectors of immunity have an antifeedant effect on this unusual parasite of rabbits.