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Guerin, Patrick

Nom
Guerin, Patrick
Affiliation principale
Fonction
Ancien.ne collaborateur.trice
Identifiants
https://libra.unine.ch/handle/123456789/310
_
0000-0002-2257-5097

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  • Publication
    Accès libre
    Time-activity budgets and space structuring by the different life stages of Varroa jacobsoni in capped brood of the honey bee, Apis mellifera
    (1997)
    Donzé, Gérard
    ;
    Guerin, Patrick 
    Varroa jacobsoni reproduces in honey bee brood cells. Here the behavioral activity and use of space by infestingVarroa females and progeny were quantified in transparent artificial brood cells. The time-activity budget of both infesting and developing mites converged toward a stable pattern which was established during the bee prepupal stage of the infesting mites and the protonymphal stage of mite progeny. The pattern was such that infesting females and offspring eventually divided their activity between the fecal accumulation on the cell wall, which served as the rendezvous site for newly molted individuals, and the feeding site prepared on the pupa by the foundress. Other parts of the cell wall were used for oviposition and molting, away from the fecal accumulation on which activity of mobile stages was concentrated. Space structuring and the time-activity budget in Varroa probably evolved to enhance the number of fertilized females produced within the capped brood, where space and time are limiting factors. These behavioral adaptations parallel those of other mite species which show group behavior within cavities.
  • Publication
    Accès libre
    Effect of mating frequency and brood cell infestation rate on the reproductive success of the honeybee parasite Varroa jacobsoni
    (1996)
    Donzé, Gérard
    ;
    Herrmann, Miriam
    ;
    Bachofen, Boris
    ;
    Guerin, Patrick 
    1. The reproductve biology of Varroa jacobsoni, whose females infest honeybee brood, was studied in natural and transparent artificial brood cells. These investigations were made under the headings of maturation behaviour and fertilization, and the influence of infestation rate of brood cells on the number of mated females produced per infesting Varroa.
    2. Mating of Varroa daughters, observed in the transparent brood cells with time-lapse video, occurs just after ecdysis and as soon as they arrive on the faecal accumulation prepared by the mother. Such females are remated for as long as no other freshly moulted daughter arrives on the faecal accumulation.
    3. The number of spermatozoa stocked in the spermatheca increases with remating, a strong indication for sperm mixing in this species when brood cells contain more than one Varroa foundress.
    4. The number of daughters per infesting mother decreases at higher rates of infestation per cell, but the proportion of such daughters with a mate rises sharply due to the higher probability of finding a male within multi-infested cells. The number of mated daughters per mother is maximal in cells with two foundress Varroa females.
    5. The frequency distributions of infesting mites in drone cells are aggregated, and approximate to negative binomial distributions.
    6. We postulate from the above that the observed non-random infestation by Varroa in drone brood augments the mite's mean reproductive success through the production of a higher number of mated daughters than the corresponding Poisson distributions would.
  • Publication
    Accès libre
    Behavioral attributes and parental care of Varroa mites parasitizing honeybee brood
    (1994)
    Donzé, Gérard
    ;
    Guerin, Patrick 
    Varroa jacobsoni, an ectoparasite of the Asian honeybee Apis cerana, has been introduced world-wide, and is currently decimating colonies of the European honeybee Apis mellifera. Varroa's reproductive cycle is tuned to that of drone cells, those mainly parasitized in the original host. We describe here how a single fertilized female, infesting a brood cell, can produce two to four adult fertilized females within the limited time span of bee development (270 h in worker and 320 h in drone cells), despite the disturbance caused by cocoon spinning and subsequent morphological changes of the bee. From observations on transparent artificial cells we were able to show how the mite combats these problems with specialized behaviors that avoid destruction by the developing bee, prepares a feeding site for the nymphs on the bee pupa, and constructs a fecal accumulation on the cell wall which serves as a rendezvous site for matings between its offspring. The proximity of the fecal accumulation to the feeding site facilitates feeding by the maturing progeny. However, communal use of the feeding site leads to competition between individuals, and protonymphs are most disadvantaged. This competition is somewhat compensated by the timing of oviposition by the mites. Use of a common rendezvous and feeding site by two or more Varroa mothers in multiinfested cells may have developed from the parental care afforded to them as nymphs.
  • Publication
    Accès libre
    Cuticle alkanes of honeybee larvae mediate arrestment of bee parasite Varroa jacobsoni
    (1994)
    Rickli, M.
    ;
    Diehl, Peter-Allan 
    ;
    Guerin, Patrick 
    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 C19–C29 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.
  • Publication
    Accès libre
    Biosynthesis, production site, and emission rates of aggregation-attachment pheromone in males of two Amblyomma ticks
    (1991)
    Diehl, Peter-Allan 
    ;
    Guerin, Patrick 
    ;
    Vlimant, Michèle 
    ;
    Steullet, Pascal
    The aggregation-attachment pheromone componentso-nitrophenol (ONP) and methyl salicylate (MS) in male Amblyomma variegatum ticks appeared after three days of feeding on the host and reached high values after about six days. Variable quantities of 1.3–7.3 μg ONP and about 0.6 μg MS were present within ticks. ONP and MS were released at the high rates of 300–1800 ng/hr and 20–600 ng/hr per male tick, respectively. After a temporary decrease, males continued to emit at high rates after nearby attachment of females. In A. hebraeum, ONP showed a similar pattern, but with a delay of about a day. A male, which had fed during 14 days, contained about 2 μg and released 225–280 ng/hr. Emission in forcibly detached males of both species dropped rapidly to low levels of less than 10 ng/hr per tick. Host skin and tick feces in the vicinity of feeding males were pheromoneimpregnated. The very high emission rates are consistent with the observations that the pheromone is an important component of the host-location mechanism of conspecifics. ONP and MS are produced in the dermal glands type 2 associated with the ventrolateral cuticle.