A singular selective capacity
But there is more and much more interesting in the origin, functionality and consequences in the detection and selective pressure of hygiene in bees and the correlation between signals from brood and characteristics of adult bees: selective hygienic behavior. From a publication by researchers from the University of Berlin (Schoning, Gisder, 2011), then supported by evidence and field tests, it emerges that the extent of the damage to the brood caused by more virulent mites capable of inducing viral infections potentially fatal to the pupae and the colony, rather than the mere presence of varroa in the brood, is the true origin of hygienic behavior. Bees express hygienic behavior as a function of the damage caused by varroa to pupae, reacting to the signals of the brood affected by pathologies, as well as for other pathologies of the brood. Varroa acts as a biological vector of a series of different viral strains with a high replicating and mutation capacity: the DWV deformed wing virus (in its variants A-B-C), the acute paralysis virus ABPV… which are among the worst enemies, subtle and lethal, for the health and survival of bees. The mechanisms of spread and contagion of the bees of these viruses are countless, however the most dangerous and epidemic spread is that through infected mites that parasitize the pupae. It is the mite that acts as an intermediate host in the transmission of increasingly virulent variants of DWV, which cause difficulty in movement (ataxia), brain infections, paralysis, abdominal impairments… and that can lead the colony to collapse. Hygienic bees recognize, uncap and remove more frequently parasitized brood by virulent mites, recognizing their peculiar and distinctive chemical signals, determining a negative selective pressure for the varroa genotypes most favorable to the replication of viral diseases. Unlike other characteristics responsible for resistance to varroa, hygienic behavior is really useful because it saves pupae infested by the mite, but which have not suffered damage and can become active members of the colony and avoids an unnecessary reduction in the breeding efficiency of the brood.
Hygienic behavior could be the main character and founded for a new selective model linked to the health of bees, which responds to today’s needs and criticalities of beekeeping, with a crucial role both in the population dynamics of varroa, and of the pathogens that it transmits.
In the next article we will begin to address the selective techniques and tools to identify hygienic bees in your breeding and we will see how the hereditary characteristics related to the health of the bees if balanced with others, as part of a selection program, can make the difference for production and performance of our hives.