Physiology of reproductive worker honey bees (Apis mellifera): insights for the development of the worker caste
Reproductive and behavioural specialisations characterise advanced social insect societies. Typically, the honey bee (Apis mellifera) shows a pronounced reproductive division of labour between worker and queen castes, and a clear division of colony roles among workers. In a queenless condition, however, both of these aspects of social organisation break down. Queenless workers reproduce, forage and maintain their colony operating in a manner similar to communal bees, rather than as an advanced eusocial group. This plasticity in social organisation provides a natural experiment for exploring physiological mechanisms of division of labour. We measured brain biogenic amine (BA) levels and abdominal fat body vitellogenin gene expression levels of workers in queenright and queenless colonies. Age, ovary activation and social environment influenced brain BA levels in honey bees. BA levels were most influenced by ovary activation state in queenless bees. Vitellogenin expression levels were higher in queenless workers than queenright workers, but in both colony environments vitellogenin expression was lower in foragers than non-foragers. We propose this plasticity in the interacting signalling systems that influence both reproductive and behavioural development allows queenless workers to deviate significantly from the typical worker bee reaction norm and develop as reproductively active behavioural generalists.
KeywordsBiogenic amines Vitellogenin Behavioural development Division of labour Temporal polyethism
We wish to thank Louise Crépeau and Branden Dunbar for sorting samples and two anonymous reviewers for their comments that significantly improved this manuscript. This research was supported by iMQRES scholarships awarded to M. Peso and N. Even, and an NIH Pioneer Award DP1 OD006416 (GER). All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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