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Thu, 29 May 2008 12:19:35 -0400
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Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
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I have spent the last month intensively studying the life span of the
honey bee. I hope to put it all together into an article someday soon.
Howevert:

> Commonly held views assume that ageing, or senescence, represents an inevitable, passive, and random decline in function that is strongly linked to chronological age. In recent years, genetic intervention of life span regulating pathways have provided compelling evidence to challenge these views.

> The honey bee has two alternative female castes (queens and workers) and a single male phenotype (the drone). Queen and worker fates are not genetically determined, and full sisters can belong to both castes. Yet, the highly reproductive queens are long-lived and can survive 2 years (Seeley 1978) or, in extreme cases up to 4 years (Botzina 1961; Page & Peng 2001). I

> n contrast, the essentially sterile workers vary in life span from a few weeks to about 1 year, whereas the drone life span is only 4–5 weeks (Winston 1987). Thus, although queens and workers can be closely related genetically, distinct longevity phenotypes emerge between them. Within the worker caste, furthermore, variation in life span develops as a function of social environmental alterations. Throughout ontogeny, worker bees change between tasks in an orderly and usually age dependent manner.

> Young workers typically perform within-nest activities like nursing larvae and after 2–3 weeks they make a transition to foraging duties collecting pollen (a protein source) and nectar (a carbohydrate source) for the colony (Winston 1987).  During favourable conditions with brood rearing, life spans of workers vary between 2 and 8 weeks. When workers switch from nest to foraging tasks, the behavioural transition is accompanied by a demographic shift due to a rapid increase in mortality as well as by manifold physiological changes (Robinson et al.1992).

> Since the age at foraging onset is usually far more variable than the duration of the forager phase, the timing of this behavioural switch is the major determinant of a bee's overall life span. Moreover, during unfavourable periods when brood rearing and foraging ceases, a third worker sub-caste develops (diutinus or 'winter' bees).

> This sub-caste is characterized by an extreme life span potential of up to 1 year (Maurizio 1950). Thereby, sister worker bees can show a vast but naturally occurring variation in longevity, albeit sharing a highly similar genetic background. Worker bees, furthermore, facilitate studies that contrast the robustness of ageing processes to their plasticity, because they display a unique feature: behavioural reversion (Robinson et al. 1992).

-- 

Ageing in a eusocial insect: molecular and physiological
characteristics of life span plasticity in the honey bee

D. Münch, G. V. Amdam, F. Wolschin
Functional Ecology 2008, 22 , 407–421
doi: 10.1111/j.1365-2435.2008.01419.x

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