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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
    Aliphatic alcohols and aldehydes of the honey bee cocoon induce arrestment behavior in Varroa jacobsoni (Acari: Mesostigmata), an ectoparasite of Apis mellifera
    (Wiley, 1998)
    Donzé, Gérard
    ;
    Silvia Schnyder
    ;
    Bogdanov, Stefan
    ;
    Diehl, Peter-Allan 
    ;
    Guerin, Patrick 
    ;
    Kilchenman, Verena
    ;
    Monachon, Florian
    The ectoparasitic mite Varroa jacobsoni reproduces in the capped brood of the honey bees Apis cerana and Apis mellifera. Observations on the reproductive behavior of the mite have shown a well-structured spatial allocation of its activity using the bee or cell wall for different behaviors. The resulting advantages for the parasite of this subdivision of the concealed brood environment suggests an important role for chemostimuli in these substrates.
    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.
  • 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.