Low fertility, fecundity and numbers of mated female offspring explain the lower reproductive success of the parasitic mite Varroa destructor in African honeybees

Authors: NGANSO, BEATRICE - International Centre Of Insect Physiology And Ecology; FOMBONG, AYUKA - International Centre Of Insect Physiology And Ecology; YUSUF, ABDULIAHI - University Of Pretoria; PIRK, CHRISTIAN - University Of Pretoria; Stuhl, Charles; TORTO, BALDWYN - International Centre Of Insect Physiology And Ecology

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2018
Publication Date: 4/17/2018
Citation: Nganso, B.T., Fombong, A.T., Yusuf, A.A., Pirk, C.W., Stuhl, C.J., Torto, B. 2018. Low fertility, fecundity and numbers of mated female offspring explain the lower reproductive success of the parasitic mite Varroa destructor in African honeybees. Parasitology. https://doi.org/10.1017/S0031182018000616.
DOI: https://doi.org/10.1017/S0031182018000616

Interpretive Summary: The varroa mite, Varroa destructor is the most serious parasite to the honeybee, Apis mellifera L. There are some honeybee populations in Africa, Apis mellifera scutellata, that can survive mite infestations without treating the hive. It has been reported that good grooming behavior in the African honey bee may be a reason why this subspecies of honey bee can tolerate mite infestation. Good hygiene and grooming behavior in the African honey bee alone cannot explain the lower mite infestations. An ARS scientists from Gainesville, FL in collaboration with researchers in Africa investigated other possible reasons to explain this phenomenon, such as the difference in mite reproduction in worker brood cells of African and European honey bees. This difference might explain the low mite numbers. Mite reproduction was similar in colonies of both honeybee subspecies. However, mite infertility and the percentage of fertile mites that reproduced successfully were higher in colonies of European honeybees than that of their African counterparts. The mortality of offspring in both sexes of mites, and the absence of male offspring may be key factors for the lower mite reproduction in the African honey bee colonies (39 - 58%) unlike those in the colonies the European honey bees (7%). The results suggested that reduced mite reproductive success may explain the slow mite population growth in African honey bee colonies. Knowledge of mite reproduction in the investigated African insect-pest system helps researchers understand domestic honey bee-parasite interactions, thus assisting with control of this important insect pest and protecting U.S. honey bees.

Technical Abstract: Although Varroa destructor is the most serious ecto-parasite to the honeybee, Apis mellifera L., some honeybee populations such as Apis mellifera scutellata in Kenya can survive mite infestations without treatment. Previously, we reported that grooming behavior could be a potential tolerant mechanism expressed by this honeybee subspecies towards mite infestation. However, both hygienic and grooming behaviors could not explain the lower mite-infestation levels recorded in these colonies. Here, we investigated the involvement of other potential resistant mechanisms including mite reproductive differences in worker brood cells of A. m. scutellata and A. mellifera hybrids of European origin to explain the low mite numbers in A. m. scutellata colonies. Mite reproductive success was similar in colonies of both honeybee subspecies. However, mite infertility and the percentage of fertile mites that reproduced successfully were higher in colonies of European honeybees than that of their African counterparts. We identified offspring mortality in both sexes and absence of male offspring as key factors accounting for the lower mite reproduction in A. m. scutellata colonies (39 - 58%) than in colonies of their European counterpart (7%). These results suggest that reduced mite reproductive success could explain the slow mite population growth in A. m. scutellata colonies.