Location: Chemistry ResearchTitle: Hygienic and grooming behaviors in African and European honeybees-New damage categories in Varroa destructor
|NGANSO, BEATRICE - African Insect Science For Food And Health (ICIPE)|
|FOMBONG, AYUKA - African Insect Science For Food And Health (ICIPE)|
|YUSUF, ABDULLAHI - African Insect Science For Food And Health (ICIPE)|
|PIRK, CHRISTIAN - African Insect Science For Food And Health (ICIPE)|
|TORTO, BALDWYN - African Insect Science For Food And Health (ICIPE)|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2017
Publication Date: 6/16/2017
Citation: Nganso, B.T., Fombong, A., Yusuf, A.A., Pirk, C.W., Stuhl, C.J., Torto, B. 2017. Hygienic and grooming behaviors in African and European honeybees-New damage categories in Varroa destructor. PLoS One. 12(6):1-14. doi:10.1371/journal.pone.0179329.
Interpretive Summary: The European honey bee is crucial in their role as pollinators for agricultural crops in the United States. Approximately one third of our foods rely on honey bees for pollination. Pollinators are critical to our Nation’s economy, food security, and environmental health. Honey bee pollination adds more than $15 billion in value to agricultural crops each year, and provides a foundation to ensure our diets are plentiful with fruits, nuts, and vegetables. The honey bee population has been in decline over the past decade. A major pest of the honey bee, Varroa destructor has had a major impact on pollinator health in North America and Europe. Varroa destructor is an external parasitic mite that transmits many honey bee viruses. However, the African subspecies Savannah honeybee in Kenya appear tolerant to the Varroa mite. This subspecies have been reported to be resilient to the mite infestation even when there is viral presence that causes colony reduction in Europe and North America. This research was performed by scientists in the Chemistry Research Unit at the Center for Medical, Veterinary and Agricultural Entomology in collaboration with International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya. An investigation into adult grooming rate, brood removal rate, mite infestation levels on adult worker bees and daily Varroa mite fall per colony were investigated in Kenya and compared to those of European honeybees in the United Sates. Three additional types of damages to the mite were found in the USA colonies and contributed significantly to the overall mite damage recorded. Adult grooming rate, brood removal rate and daily Varroa mite fall per colony were similar in the Savannah and European honeybee. Varroa mite infestation levels in the Savannah honeybee were three times lower than those of the European honeybees. Our research suggests that the ability of the Savannah honeybee to survive mite infestation is dependent on host factors rather than parasite virulence. The reason for the reduced Varroa mite infestation level in the Savannah honeybee was not identified in this study. Although, the information collected is a significant step towards understanding the adaptive processes of mite resistance in honeybees worldwide.
Technical Abstract: Varroa destructor is an ectoparasitic pest of honeybees, and a threat to the survival of the apiculture industry. Several studies have shown that unlike European honeybees, African honeybee populations appear to be minimally affected when attacked by this mite. However, little is known about the underlying drivers contributing to survival of African honeybee populations against the mite. We hypothesized that resistant behavioral defenses are responsible for the survival of African honeybees against the ectoparasite. We tested this hypothesis by comparing grooming and hygienic behaviors in the African savannah honeybee Apis mellifera scutellata and the European honeybee A. m. carnica against the mite. Grooming behavior was assessed by determining adult mite infestation levels, daily mite fall per colony and percentage mite damage (as an indicator of adult grooming rate), while hygienic behavior was assessed by determining the brood removal rate after freeze killing a section of the brood. Our results identified two additional undescribed damaged mite categories along with the six previously known damage categories associated with the grooming behavior of both honeybee subspecies. Interestingly, whereas adult mite infestation level was approximately three-fold higher in A. m. carnica than in A. m. scutellata, however, brood removal rate, adult grooming rate and daily mite fall were similar in both honeybee subspecies. Unlike A. m. carnica, adult grooming rate and brood removal rate did not correlate with brood removal rate in A. m. scutellata. Our results provide valuable insights into the tolerance mechanisms that contribute to the survival of A. m. scutellata against the mite.