Reproduction of distinct genotypes of varroa destructor on honeybee worker brood of the European honey bee apis mellifera and the Asian honey bee apis cerana

Authors: LI, WENFENG - GUANGDONG UNIVERSITY; WANG, CHENG - GUANGDONG UNIVERSITY; HUANG, ZACHARY - MICHIGAN STATE UNIVERSITY; Chen, Yanping - Judy; HAN, RICHOU - GUANGDONG UNIVERSITY

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2019
Publication Date: 10/25/2019
Citation: Li, W., Wang, C., Huang, Z., Chen, Y., Han, R. 2019. Reproduction of distinct genotypes of varroa destructor on honeybee worker brood of the European honey bee apis mellifera and the Asian honey bee apis cerana. Insects. https://doi.org/10.3390/insects10110372.
DOI: https://doi.org/10.3390/insects10110372

Interpretive Summary: The external parasitic, Varroa mite, was originally a parasite of the Asian honey bee and has become the single most detrimental pest of the European honey bee following a jump from its original natural host to the new host over a half-century ago. Varroa mites are divided into genetically distinct subpopulations, known as haplotypes, based on their host geographical origins. We conducted a study to compare the reproduction of two Varroa subpopulations, Korea haplotype and China haplotype, in original and new hosts. Our results showed that Varroa mites of the Korea haplotype derived from European honey bees were able to reproduce in both European honey bees and Asian honey bees with a better reproductive performance in the new hosts. In contrast, Varroa mites of the China haplotype derived from Asian honey bees were entirely sterile in European honey bees. This study provides an important insight into host-parasite interactions and the reproductive success of the Varroa mites in honeybees and will have the potential to make contributions to the bee pest management programs.

Technical Abstract: Honey bees play important roles in pollination for many crops and wild plants, but have been facing great threats posed by various pathogens and parasites. Among them, Varroa destructor, an obligate ectoparasite of honey bees, is considered the most dangerous. Within last century, V. destructor shifted from the original host, the Asian honey bee Apis cerana to the new host, European honey bee A. mellifera However, the reproduction of Varroa mites, especially different haplotypes in the two hosts is still largely unknown. In this study we first investigated the existing Varroa haplotypes in local colonies in southern China, and then compared the reproduction of different haplotypes on the worker brood of both the original and new host by artificial inoculation. We confirmed that there are two haplotypes of V. destructor in southern China, one is Korea haplotype and the other is China haplotype, and the two types specifically parasitized different honey bee species. Moreover, Varroa females from A. mellifera (Korea haplotype) have the capability to reproduce in the worker cells of both the original and new hosts, however, better reproductive performance was achieved in the new host A. mellifera with significant higher fecundity (number of offspring per mother mite) and reproductive rate (number of adult daughters per mother mite), suggesting the parasite gains a higher level of fitness following the host shift. The data further show that a short stayof Varroa females on the A. cerana worker brood decreased their fecundity, and in particular the real reproductive rate in a time-dependent manner, indicating that the A. cerana worker cells may inhibit Varroa reproduction. In contrast, Varroa mites derived from A. cerana colonies (China haplotype) were entirely sterile in A. mellifera worker cells during two sequential inoculations, while the controls using A. mellifera derived Varroa (Korea haplotype) reproduced normally. In addition all of the infertile mites were found to defecate on the abdomen of the bee brood for an unknown reason. In summary, we have revealed that two haplotypes (Korea and China) of V. destructor have different reproduction rates in the original and new host worker cells, providing new insights into the diversity and complexity of the reproduction of V. destructor.