Olfactory and behavioral response thresholds to odors of diseased brood differ between hygienic and non-hygienic honey bees ( Apis mellifera L.)

Abstract

Through the use of proboscis-extension reflex conditioning, we demonstrate that honey bees (Apis mellifera L.) bred for hygienic behavior (a behavioral mechanism of disease resistance) are able to discriminate between odors of healthy and diseased brood at a lower stimulus level than bees from a non-hygienic line. Electroantennogram recordings confirmed that hygienic bees exhibit increased olfactory sensitivity to low concentrations of the odor of chalkbrood infected pupae (a fungal disease caused by Ascosphaera apis). Three-week-old hygienic bees were able to discriminate between the brood odors significantly better than three-week old non-hygienic bees. However, the differential performance in brood odor discrimination was primarily genetically based, not a direct result of age, experience, or the temporary behavioral state of the bee. Lower stimulus thresholds for both the olfactory and behavioral responses of hygienic bees may facilitate their ability to detect, uncap and remove diseased brood rapidly from the nest. In contrast, non-hygienic bees, possessing higher response thresholds, may not be able to detect diseased brood as easily. Our results provide an example of how physiological and behavioral differences between the hygienic and non-hygienic honey bee lines, operating at the level of the individual, could produce colony-specific behavioral phenotypes.

Behavioural, physiological and molecular changes in alloparental caregivers may be responsible for selection response for female reproductive investment in honey bees

“…However, the complex phenotype of RJBs seems to involve changes in the sensitivity of the antennae that appear to lower the nurse bees' response threshold to larval pheromones without affecting any larval signalling. Breeding efforts for hygienic honey bees have also increased olfactory sensitivity of the antennae to discriminate diseased from healthy brood (Guarna et al, 2015), lowering their response thresholds (Masterman et al, 2001). Together, studies in honey bees support the central role of the insect antenna for behavioural tuning and rapid evolutionary change (Leal, 2013;Schott et al, 2013) but we cannot rule out additional differences in the central nervous system.…”

Phenotypic and Genetic Analyses of the Varroa Sensitive Hygienic Trait in Russian Honey Bee (Hymenoptera: Apidae) Colonies

“…It has been found that the “cost” of hygienic removal of Varroa -infested cells is similar for resistant and susceptible stocks so that the difference in actual removal is probably due to differences in detection ability [ 44 ]. Indeed, through proboscis extension reflex conditioning, [ 45 ] showed that, in comparison to susceptible bees, hygienic bees resistant to Chalkbrood disease needed a lower stimulus to detect diseased brood. Alternatively, two stocks may differ in the level of mites tolerated by the colony; resistant stocks such as VSH and RHB having a lower behavioural threshold to mite density [ 15 ].…”

Resisting majesty: Apis cerana, has lower antennal sensitivity and decreased attraction to queen mandibular pheromone than Apis mellifera

“…To measure antennal sensitivities, we used electroantennograms (EAG), which are commonly used to measure olfactory stimulus sensitivity in honey bees18 and have been employed to measure worker responses to Am QMP1. In both species, the slope and shape of EAG antennal responses to different compounds were similar, and exhibited a fast recovery to baseline (Fig.…”