Juvenile mortality of the female descendants in the ectoparasitic miteVarroa jacobsoniin worker brood ofApis mellifera

Abstract

During the autumn of 1996 and 1997 in Thessaloniki (Greece) juvenile mortality OM) of the mite Varroa jacobsoni was studied in worker brood cells of frozen combs from 21 Apis mellifera macedonica colonies. The infestation level of the colonies varied between 8% and 35%. Sealed brood cells (n = 8454) containing a healthy worker pupa older than the 'pale eyes' stage or a resting adult were examined. The cells examined were singly infested by a fertile V. jacobsoni with normal offspring in 92% of the cases. A total number of 3543 developing fertile V. jacobsoni female descendants (fd) was studied. During the mobile phases the losses of the parasite in the first, second and third fd were 2.8%, 13.8%, 30.4%, respectively. Under natural conditions no death factors act against the first fd until it reaches the second immobile phase, or deutochrysalis phase (DCHR) in the worker brood cell. For the subsequent fd, malnutrition possibly plays the most important role during the pre-DCHR mobile phases. During the immobile phases the main losses of the first fd occur in the DCHR phase. On average, the death rates for the first, second and third DCHR were 6.2%, 11.3% and 14.2%, respectively, in worker brood cells containing maturing pupae. Rates of losses for the DCHR of the three fd determined in cells containing the resting adult were 15.8%, 37.1% and 56.9%, respectively. The general losses concerning all developing phases of the mite, i.e. pre-DCHR and DCHR, for the first, second and third fd in worker brood cells were 18.6%, 50.9% and 87.3%, respectively. Death of the DCHR of V. jacobsoni in the worker brood cell of A mellifera is connected with aging of the host. This is based on the following: (a), practically no death of DCHR was observed as long as the host retained its white body colour; dead DCHR appeared first when the aging worker pupa acquired yellow body colour; and (b), the death rate of DCHR increases as the worker pupa becomes older. The possible influence of different natural or artificial factors causing death of female DCHR is discussed. Downloaded by [University of Sherbrooke] at 15:01 10 April 2015 26

Varroa destructor rearing in laboratory conditions: importance of foundress survival in doubly infested cells and reproduction of laboratory-born females

“…However, this hypothesis was not tested in our study and implies that the initiation of reproduction is more related to a series of signals independent from the female mite and much less related to the energy stocks of the parasite. Although surprising, this is concordant with other observations about the initiation of reproduction (Frey et al 2013) and with the fact that the fourth (and to a lesser extent the third) egg laid by the female in a worker cell are often observed even though they have no chance of developing into adults (Martin 1994;Donzé et al 1996;Ifantidis et al 1999). A second hypothesis would be that the loss of daughters is not related to the energy but to external factors.…”

“…In many studies of V. destructor reproduction, the frames were frozen so the difference between dead and living females might not have been made with certainty (Ifantidis 1984;Martin 1994;Ifantidis et al 1999). Our study shows that the mortality of foundresses in doubly and singly infested cells could be an important factor impacting the number of offspring.…”

Biology and control of Varroa destructor

“…For example, in 11-21% of the brood cells the male is lacking (Donzé et al, 1996;. The mortality of mite offspring seems to be a main factor for differences in the reproductive rate and varies according to climate, season and honey bee subspecies (Eguaras et al, 1995;Ifantidis et al, 1999;Mondragón et al, 2005Mondragón et al, , 2006. A strange case of mite mortality is reported from the pseudo clone A. mellifera capensis in South Africa: The mortality of Varroa offspring in the brood cells of the parasitic A. mellifera capensis is somewhat higher compared to that in A. mellifera scutellata, due to a ''trapping effect" in the upper part of the larger capensis brood cells (Martin and Kryger, 2002).…”

Investigating the influence of postcapping period on varroa mite infestation

“…Varroa mother mites start laying eggs 70 h (2.92 days) after cell capping (Ifantidis, Karamanidou, & Katikou, 1999;Steiner, Diehl, & Vlimant, 1995), while the first egg is unfertilized and the next eggs up to six eggs are laid in 30 h (1.25 days) intervals (Ifantidis, 1990;Martin & Kryger, 2002;Rehm & Ritter, 1989). It will take 5.8-6.6 days for the mite offsprings (female and male, respectively) to become adult (Donzé & Guerin, 1994;Ifantidis, 1990;Martin & Kryger, 2002;Rehm & Ritter, 1989).…”