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From:
"Peter L. Borst" <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Mon, 12 Nov 2007 08:46:27 -0500
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Greetings
One possible cause of honey bee disappearance has received little
attention. Brood that is exposed to unfavorable temperatures can
result in "brain damaged" bees which are unable to function normally.
This was suggested by Ben Oldroyd:

> Remarkably, honey bees maintain the temperature of their brood nest within ± 0.5 °C of 34.5 °C [94.1 F], despite major fluctuations in ambient temperature. If the brood is incubated a little outside this range, the resulting adults are normal physically, but show deficiencies in learning and memory. Workers reared at suboptimal temperatures tend to get lost in the field, and can't perform communication dances effectively . Although entirely a hypothesis, I suspect that if colonies were unable to maintain optimal brood nest temperatures, CCD-like symptoms would be apparent. ( "What's Killing American Honey Bees?" Benjamin P. Oldroyd. www.plosbiology.org )

* * *

Martin Lindauer writes:

> It has been known for many years that honey bees hatch and progress through a number of stages within the hive during which they will carry out various tasks ranging through cell cleaning, nursing, comb building, entrance guarding, and foraging. It is also known that although cell cleaning and foraging are the specialties of the youngest and the oldest bees, the bees between these extremes carry out a number of different tasks and will frequently switch from one task to another in a short space of time. Different individuals also will spend different amounts of time on in-hive activities compared with outside activities whereas others may never forage at all. The reason for these differences between bees has been the subject of speculation, and we would suggest here that the temperature regime to which they were subjected as pupae may play an important role.

> Bees raised artificially at constant temperatures on the lower end of the naturally occurring brood nest temperature range perform less well in dance communication and scent learning. Under natural conditions, this would lead to ''bad dancers,'' as von Frisch termed forager bees with a low probability to dance and those performing only few dance circuits compared with ''good dancers'' (unpublished protocols by K. von Frisch, available from J.T.). Such behavior will lead to less nectar inflow into the colony  because no dances or short dances with only few circuits will attract no or few recruits. Also, a highly variable waggle phase should guide recruited bees to areas scattered around the goal because the feeder distance is coded by the duration of the waggle phase.

> We have qualitative evidence that exposing the pupae of bees to a temperature of 32°C may have a more far-reaching effect than producing poor dancers. Of the 80 bees that were treated at 32°C and introduced to the observation hive, only very few remained at the end of the 2-week period. The others apparently left the hive and never returned. One could speculate that these animals, seemingly perfectly able to carry out the in-hive nest duties, had trouble finding their way back to the hive after undertaking their orientation flights, and, indeed, some of these bees were found in hives in the neighborhood of their own. The learning and memory consolidation tests confirm that not only are the 32°C-raised bees poor dancers, they also are bad learners. Learning and memory consolidation, therefore, do appear to be critically important for foraging.

>  To investigate the possible consequences of brood-temperature regulation in honey bee colonies on the quality of behavioral performance of adults, we placed honey bee pupae in incubators and allowed them to develop at temperatures held constant at 32°C, 34.5°C, and 36°C. This temperature range occurs naturally within hives. On emergence, the young adult bees were marked and introduced into foster colonies housed in normal and observation hives and allowed to live out their lives. No obvious difference in within-hive behavior was noted between the temperature-treated bees and the foster-colony bees.

> However, when the temperature-treated bees became foragers and were trained to visit a feeder 200 m from the hive, they exhibited clear differences in dance performance that could be correlated with the temperatures at which they had been raised: bees raised at 32°C completed only  20% of the dance circuits when compared with bees of the higher-temperature group. Also, the variance in the duration of the waggle phase is larger in 32°C-raised bees compared with 36°C-raised bees. All other parameters compared across all groups were not significantly different.

> Bees raised at 36°C performed as expected for bees typically classified as "good learners," whereas bees raised at 32°C and 34.5°C performed significantly less well. We propose that the temperature at which pupae are raised will influence their behavioral performance as adults and may determine the tasks they carry out best inside and outside the hive. ( "Behavioral performance in adult honey bees is influenced by the temperature experienced during their pupal development." Communicated by Martin Lindauer, University of Würzburg, Würzburg, Germany, April 21, 2003 )


* * *

This is confirmed by research by Claudia Groh, et al:

> In the present study, we investigated whether small changes in the temperature normally maintained during pupal development of honey bees may influence the synaptic maturation in the developing nervous system. The results show that different rearing temperatures cause area- and modality-specific effects on synaptic complexes within the mushroom bodies (MBs), higher integration centers in the insect brain. Effects occurred within the range of temperatures normally maintained by brood-temperature control. Potential consequences of changes in the synaptic circuitry for neuronal plasticity and behavioral performance are discussed. ( "Synaptic organization in the adult honey bee brain is influenced by brood-temperature control during pupal development." Claudia Groh, Jurgen Tautz, and Wolfgang Rossler. www.pnas.org )

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