Changeling Varroa

Newly-Emerged Bee With Varroa Mites (The Brown Discs)
Newly-Emerged Bee With Varroa Mites (Brown Discs)

At the Leiston and District Beekeepers’ Association AGM, some exciting new research into varroa mites was disclosed. (The L&DBKA partly sponsors an Eastern Area Research Student (EARS) project and that student is associated with this research).

These new insights into the fiendish cunning of these deadly bee parasites showed that varroa mites employ chemical camouflage to move, undetected, from the bee, on which they feed, into the brood cells, where they reproduce. Since the odour of a bee is very distinct from the odour in the brood cell, this is quite a transition.

Essentially, a varroa mite can change its chemical profile in between 3 and 9 hours when switching between bee or brood cell hosts and thus remain undetected by the bees. Even a dead varroa mite is capable of mimicking its host’s odour.

Here is the Abstract from The Journal of Chemical Ecology: Social insect colonies provide a stable and safe environment for their members. Despite colonies being heavily guarded, parasites have evolved numerous strategies to invade and inhabit these hostile places. Two such strategies are (true) chemical mimicry via biosynthesis of host odor, and chemical camouflage, in which compounds are acquired from the host. The ectoparasitic mite Varroa destructor feeds on hemolymph of its honey bee host, Apis mellifera. The mite’s odor closely resembles that of its host, which allows V. destructor to remain undetected as it lives on the adult host during its phoretic phase and while reproducing on the honeybee brood. During the mite life cycle, it switches between host adults and brood, which requires it to adjust its profile to mimic the very different odors of honey bee brood and adults. In a series of transfer experiments, using bee adults and pupae, we tested whether V. destructor changes its profile by synthesizing compounds or by using chemical camouflage. We show that V. destructor required direct access to host cuticle to mimic its odor, and that it was unable to synthesize host-specific compounds itself. The mite was able to mimic host odor, even when dead, indicating a passive physico-chemical mechanism of the parasite cuticle. The chemical profile of V. destructor was adjusted within 3 to 9 h after switching hosts, demonstrating that passive camouflage is a highly efficient, fast and flexible way for the mite to adapt to a new host profile when moving between different host life stages or colonies.

That’s just not cricket !

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