Evidence for Passive Chemical Camouflage in the Parasitic Mite Varroa destructor

Abstract

-Social insect colonies provide a stable and safe environment for their 34 members. Despite colonies been heavily guarded, parasites have evolved numerous 35 strategies to invade and inhabit these hostile places. Two common strategies are chemical 36 mimicry via biosynthesis of the hosts' odour or chemical camouflage were compounds 37 are acquired straight from the host. The ectoparasitic mite Varroa destructor feeds on the 38 heamolymph of its honeybee host Apis mellifera and uses chemical mimicry to remain 39 undetected as it lives on the adult host during its phoretic phase or while reproducing on 40 the honeybee brood.. During the mite life cycle it switches between host adults and 41 brood, which requires it to adjust its profile to mimic the very different odours of 42 honeybee brood and adults. In a series of transfer experiments using adult bees and 43 pupae, we tested whether V. destructor does this by synthesising compounds or using 44 chemical camouflage. We show that V. destructor required direct access to the host 45 cuticle to mimic its odour and was unable to synthesise host-specific compounds itself. destructor was adjusted within three to nine hours after switching hosts, demonstrating 49 that passive camouflage is a highly efficient, fast and flexible way for the mite's to adapt 50 to a new host's profile when moving between different host life stages, or host colonies.

Varroa destructor changes its cuticular hydrocarbons to mimic new hosts

“…This agrees with the previous findings that mites were more similar to their immediate host's developmental stage [6,7,11], but our study used different host species to challenge the mite's ability to modify its HC. Because mites clustered according to their new hosts, but not according to their original hosts, we assumed that these mites changed their HC profiles after being transferred to the new host.…”

“…A recent study [7] showed that mites are not actively mimicking their hosts, instead by passively using host materials via contact. Our data here suggest that, at least for mites from Ac, some active processes might be involved because they mimicked their hosts better.…”

Varroa destructor Mites Can Nimbly Climb from Flowers onto Foraging Honey Bees

“…However, the fact that our focal mites and foraging bees were both from the same colony does mean that this study neglects possible effects of chemical adaptation between the mites and bees. Varroa mites have been shown to passively absorb the cuticular hydrocarbon profile of their host hive [25,26]. Therefore, a forager might have had an easier time detecting and removing a mite if the mite had the hydrocarbon profile of a foreign colony, (though mite grooming-avoidance behavior suggests increased detectability may not be sufficient to stop infestation.)…”

“…Since mites prefer to use nurse bees as hosts over foragers [30,31,32], perhaps movement to these non-feeding refugia provides a safe place for a mite to wait until the forager it has infested brushes past a nurse bee in the hive. Kather and colleagues have shown that mites entering a new colony require a period of at least three hours to chemically adapt to the odors of their new hosts, [26] which offers another explanation for why mites on flowers would initially move to non-feeding sites which offer refuge from host grooming.…”

Myrmecophily and Myrmecophagy of Attacobius lavape (Araneae: Corinnidae) on Solenopsis saevissima (Hymenoptera: Myrmicinae)

“…This behavior suggests that the renewal or the restoration of the cuticle chemical profile by the spider is not regulated via biosynthesis, but by continuous exogenous transfer, indicating the use of chemical camouflage to remain in the hosting colony (Dettner & Liepert, 1994). When the Varroa destructor Anderson and Trueman, 2000 mite was experimentally introduced in one colony of a different host bee species (Apis cerana Fabricius, 1793), it acquired a chemical profile similar to the new hosting species demonstrating chemical camouflage of the parasite mite (Kather et al, 2015). In fact, no case of chemical mimicry by biosynthesis has been attributed to the myrmecophilous spiders, and the integration with the ant colonies occurs by the contact with the nest material, contact with the workers or by the predation of larvae and pupae (Cushing, 2012), yet some cuticular hydrocarbon studies are necessary to confirm this hypothesis.…”