Reproduction of parasitic mites Varroa destructor in original and new honeybee hosts

Abstract

The ectoparasitic mite, Varroa destructor, shifted host from the eastern honeybee, Apis cerana, to the western honeybee, Apis mellifera. Whereas the original host survives infestations by this parasite, they are lethal to colonies of its new host. Here, we investigated a population of A. cerana naturally infested by the V. destructor Korea haplotype that gave rise to the globally invasive mite lineage. Our aim was to better characterize traits that allow for the survival of the original host to infestations by this particular mite haplotype. A known major trait of resistance is the lack of mite reproduction on worker brood in A. cerana. We show that this trait is neither due to a lack of host attractiveness nor of reproduction initiation by the parasite. However, successful mite reproduction was prevented by abnormal host development. Adult A. cerana workers recognized this state and removed hosts and parasites, which greatly affected the fitness of the parasite. These results confirm and complete previous observations of brood susceptibility to infestation in other honeybee host populations, provide new insights into the coevolution between hosts and parasites in this system, and may contribute to mitigating the large‐scale colony losses of A. mellifera due to V. destructor.

Divergent evolutionary trajectories following speciation in two ectoparasitic honey bee mites

“…In contrast to the population collapses of A. mellifera , the host-parasite interaction with A. cerana is a balanced relationship in which a tolerance equilibrium is maintained by a range of parasite adaptations and host counter-adaptations 32–37 . Specifically, the eastern honey bee has impressive host defense traits, including (i) self and collective grooming behaviors 38 , (ii) hygienic behavior where mites are removed from infested cell 39 , (iii) worker brood death that stops parasite reproduction 34,35 , (iv) entombing of mites in drone brood, and (v) shorter worker development cycle limiting the mites’ offspring number 33 . By contrast, most western honey bee populations lack these defensive mechanisms, and hives collapse quickly after Varroa infestation.…”

Natural selection, selective breeding, and the evolution of resistance of honeybees (Apis mellifera) against Varroa

“…This often results in the removal of phoretic adult mites and inflicts significant mortality among them. The uncapping of worker cells with reproducing Varroa and the subsequent removal of the parasitized pupae result in the removal of mite offspring before they have been able to reproduce [5]. This is an important factor in preventing the mite population to grow to harmful densities.…”

“…While it does not cause colony mortality in its original host A. cerana [3,4], it became and remains devastating to apiculture and to natural populations of A. mellifera in Europe and feral populations in North America. One reason why Varroa is so virulent on A. mellifera is that it can breed in worker brood and so achieve a long reproductive season, while in A. cerana, pupae from worker cells with reproducing mites are always removed [5] and breeding is restricted to the short season during which drones are produced.…”

Genome-Wide Identification of Long Non-coding RNAs in the Gravid Ectoparasite Varroa destructor

“…Considering these timing, we collected the mites 48 h later after the mite was introduced into the freshly capped cells. The artificial infestation has been established to be a suitable method for V. destructor research (Dietemann et al, 2013;Lin et al, 2018;Häußermann et al, 2019), and mites parasitized in the capped brood cells are less variable in physiology and fitness than on the adult bee bodies (Milani, 1995). The mites collected were further confirmed gravid with dilated post-abdomen, from which we can even see the eggs inside under microscope (Supplementary Figure 1B).…”

“…destructor mites were collected from experimental A. mellifera colonies untreated for half a year, which were located in Yangzhou University of China. We employed the mites to mimic phoretic phase before experimental infestation to obtain similar physiological status (see details in Lin et al, 2018). Each freshly capped worker cell was introduced with a mite, and gravid adult mites were collected from sealed worker brood with the tweezers and the paint brushes 2 days later after infestation ( Supplementary Figure 1).…”