winter bees

[chris]

Could somebody explain to me how a winter bee becomes a winter bee? Is there some basic difference , or is it simply that a *summer* worker uses up less fat by not spending much time wearing itself out as a nurse bee?

[Jon]

There is a load about worker longevity in this report.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2398712/

edit
and this one

http://www.uncg.edu/mat/bio-math/downloads/Amdam2002.pdf

[chris]

Thanks for those links Jon- they contain what I wanted to know.
So, perhaps you could comment on the following. September has been exceptionally dry this year and the nectar/pollen sources have been very limited.When I checked my hives last week, in all but 2 the queen had already stopped laying, and in those 2 the brood was reduced to half a frame. Stores were about the same as at the end of August. I decided not to feed because I didn't want the queen to start laying again (there is no late flow here). According to those links:
1) lack of forage diminishes the number of bees foraging
2) lack of foraging diminishes aging
3) lack of nursing brood keeps the protein levels high in house bees and also diminishes aging.
I assume the bees are already entering winter mode and so I will not interfere any more.
The longer broodless period should be useful against varroa at this time of year.

[Jon]

There were a lot of snippets of useful info, especially in the second link.

I must read up more on vitellogenin as this seems to play a key role in the winter bees.


If the workers
had to eat pollen and distribute protein during
winter to replenish their protein stores, this
would have caused enhanced energy consumption
in the winter cluster. Selection for physiological
mechanisms promoting accumulation of
a storage protein in the autumn large enough to
last until spring solves this problem, and given
that the essential features of our mathematical
model is correct, vitellogenin is the most likely
protein candidate to have been used for this
purpose.


Furthermore, if it can be
shown that it is the lack of vitellogenin that
causes the dramatic reduction in the proportion
of normal plasmocytes in the haemolymph of
honeybee foragers, this would imply that there is
a direct link between vitellogenin and ageing

The other interesting bit was about how varroa, nosema and some chemicals can affect the levels of vitellogenin and consequently the longevity of the bee.


Various pathogens reduce the protein content
of honeybee workers (Weinberg & Madel, 1985;
Schneider & Drescher, 1987; Schatton-Gadelmayer
& Engels, 1988). Infestation by the
ectoparasite Varroa destructor causes a significant
reduction in haemolymph protein levels and
the diameter of the HPG acini (Schneider &
Drescher, 1987). Spores from the microsporidian
pathogen Nosema apis and the insecticides BPTI
(bovine pancreatic trypsin inhibitor) and SBTI
(Kunitz soybean trypsin inhibitor) have similar
effects, inhibiting the release of essential amino
acids from consumed pollen (Burgess et al.,
1996; Malone & Gatehouse, 1998).



According to Moritz (1981), a
Varroa mite will consume 0.25 ml haemolymph
daily from its adult host, which suggests that the
vitellogenin consumption from a winter bee is
approximately 8 mg day1. This implies that the
lifespan of a worker in the winter season would
be reduced by 30% if it gets exposed to only a
single Varroa mite.

[Adam]

Some weekend reading for me Jon!
Thanks for the links.

[Jon]

I came across a link to this work on vitellogenin on Bee-L which appears to be a new discovery.



One of these molecules is a protein called vitellogenin. "Simply put, the more vitellogenin in bees, the longer they live. Vitellogenin also guides bees to do different social tasks, such caregiving or foraging. It also supports the immune function and is an antioxidant that promotes stress resistance.

http://www.eurekalert.org/pub_releases/2011-11/nuol-hbm112811.php