Honey bees (Apis mellifera) preselected for Varroa sensitive hygiene discriminate between live and dead Varroa destructor and inanimate objects

Abstract

Varroa destructor is one of the main causes of colony losses of the western honey bee (Apis mellifera). Many efforts exist to breed honey bees resistant to V. destructor. Varroa sensitive hygiene (VSH) is a commonly selected behavioural trait; VSH workers remove the pupae of mite infested brood cells with high efficiency, interrupting the reproduction of the mite. The cues and triggers for this behaviour are not yet fully understood. To determine what elicits this removal behaviour, we examined preselected VSH workers´ responses to four different groups of objects inserted into freshly capped cells: live mites, dead mites, odour reduced mites, and glass beads. These were also compared to control cells that were opened and closed without inserting any object. The pupae in cells containing inorganic objects (glass beads) were removed at similar rates to the control, demonstrating that an object alone does not trigger a removal response. Dead and odour reduced mites were removed at a higher frequency than control cells, but less frequently than live mites. Workers sometimes removed items resting near the top of the cell without removing the pupa. Our results demonstrate that although mite odour from dead mites triggers removal behaviour, the pupa of cells containing live mites were removed more frequently, suggesting that other cues (i.e. odour from feeding wound) or signals (i.e. pupal movement to signal distress) are important. Future research should focus on elucidating these other cues or signals from the brood and mites, as mite presence alone seems to be insufficient.

Reproduction of Varroa destructor depends on well-timed host cell recapping and seasonal patterns

“…This cell section, however, is especially exposed to disturbance by worker bees opening the cell lid (REC). Eggs laid near the cell lid are thus at risk to be removed by adult bees, as was recently shown for artificially inserted items 39 . Oviposition in the anterior part of the brood cell is also common for the second egg 31 , which develops into the female with the best chances to reach maturity 33 .…”

“…Termination rates in our dataset were correlated with bee and brood infestation as well as REC measurements at the colony level (Table 3 ), supporting these earlier findings 38 . Therefore in some cases, termination of initially uncapped cells may be a second step in a complex detection cascade leading to VSH as suggested before 17 , 39 . Nevertheless, cells being recapped instead of terminated after initial uncapping also showed significantly increased MNR values (Table 1 ).…”

“…Also, the previously supposed 24 mother mite emigration during uncapped brood periods seems to occur very rarely after natural infestation, since hardly any abandoned cells with mite faeces or orphan families were found. However, such emigration or removal events have been reported for cells artificially infested with mites deriving from the dispersal phase 39 .…”

Mite non‐reproduction is not a consequence of the brood removal behavior of varroa sensitive hygiene honey bee colonies (Apis mellifera)

“…The reproductive cycle of a varroa mite is thus interrupted by the removal of brood. While the pupae are removed by the workers, only a small percentage of mites are killed or damaged in the process (Bienefeld et al, 1999;Lodesani et al, 1996) (Ivanova & Bienefeld, 2023;Mondet et al, 2021;Nazzi et al, 2004;Schöning et al, 2012;Sprau et al, 2021Sprau et al, , 2023Wagoner et al, 2018).…”

Creation of a Biobank of the Sperm of the Honey Bee Drones of Different Subspecies of Apis mellifera L.

“…During the natural spread of the honey bee Apis mellifera L., it formed various subspecies and ecotypes adapted to specific climatic zones [18,19]. In addition to naturally occurring subspecies, work is being carried out to develop various breeding stocks and lines that differ in terms of their economically useful traits [20][21][22][23]. Due to human economic activity, the boundaries between subspecies began to blur, and some subspecies were absorbed by others [24,25].…”