Honey bees, Apis mellifera L., bred for hygienic behavior uncap and remove diseased and mite-infested brood. We hypothesized that within a colony bred for hygienic behavior, there would be differences in olfactory sensitivity among bees of the same age. We predicted that bees that initiate the behavior by perforating and uncapping brood would have greater olfactory sensitivity to the odor of the diseased brood, and would be better able to discriminate between odors of healthy and diseased brood, compared to bees that complete the behavior by removing the uncapped brood from the cells. Electroantennogram recordings of 15- to 21-day-old bees from three colonies demonstrated that bees collected while uncapping dead brood had significantly greater olfactory sensitivity to all concentrations of diseased brood odor compared to bees collected while removing brood. Proboscis-extension reflex discrimination conditioning demonstrated that 15- to 21-day-old bees collected while uncapping discriminated significantly better and generalized significantly less between the odors of diseased and healthy brood compared to bees collected while removing, when the odor of diseased brood was rewarded, but not when the odor of healthy brood was rewarded. Bees collected while uncapping brood that had been pierced with a pin had significantly less olfactory sensitivity than bees collected while uncapping freeze-killed brood, most likely because the pierced brood had greater stimulus intensity. Initiation of hygienic behavior depends on the olfactory sensitivity of the bee and stimulus intensity of the abnormal brood. Differential olfactory sensitivity and responsiveness among hygienic bees could lead to the apparent partitioning of the behavior into uncapping and removing components.
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Acknowledgements We wish to acknowledge Rocco Ross, Jessica Fiedler, and Rebecca Masterman for their assistance with the EAG and PER experiments, Gary Reuter and Jenny Warner for assistance with bee colonies, and Karen Mesce, Arathi Seshadri, and particularly Ian Burns for helpful comments on the manuscript. Special thanks to Lionel S. Gonçalves for his support and advice. The research was supported by FAPESP (Fundaç¼o de Amparo a Pesquisa do Estado de S¼o Paulo) Brasil (to K. Gramacho) and by NSF IBN-9722416 (to M. Spivak). The experiments comply with the “Principles of animal care” publication No. 86–23, revised 1985, of the National Institute of Health.
Copyright 2008 Elsevier B.V., All rights reserved.
- Apis mellifera
- Hygienic behavior
- Proboscis-extension response conditioning
- Task partitioning