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Bad Dancers: Childhood chills give bees six left feet

Susan Milius

Honeybees kept just a bit cool when young turn into lousy dancers.

photo

BEE PREPARED. A foraging honeybee is best equipped for dance communication if it developed in a warm nursery during its critical pupal stage.

F. Bock/Würzburg Bee Group

That's a serious problem for adult honeybees, explains Jürgen Tautz of the Universität Würzburg in Germany. When a worker bee comes home after finding food, she does a little dance to communicate the location of her discovery. A bad dancer can leave her nest mates without clear directions or much motivation to visit her windfall.

Bees that develop in incubators at the cool end of honeybees' hive temperatures didn't dance as well as bees kept at the temperature in the upper range, report Tautz and his colleagues in an upcoming Proceedings of the National Academy of Sciences. Also, the chilly-pupahood bees didn't perform as well as other bees in a learning test.

"I don't think anybody has ever looked at this before," comments Gloria DeGrandi-Hoffman of the Carl Hayden Bee Research Center in Tucson. Before this, when researchers came across bee variation, they focused on the insects' genetics, but the paper makes a dramatic reminder that temperature and other quirks of the environment need consideration, too, says DeGrandi-Hoffman.

Bees lack the specialized physiology that keeps birds and mammals at even temperatures. Yet honeybees regulate temperatures for their offspring by carrying water to the hive and cooling it through evaporation or by madly flexing their muscles to generate heat.

Such work takes a lot of energy, and Tautz and his colleagues calculate from other research that a typical hive, with thousands of workers, devotes to temperature regulation about 40 percent of the energy supplied by the nectar that workers collect during the year.

That investment suggests that temperature management matters a great deal. To explore its ramifications, the researchers incubated three broods of youngsters at 32°C, 34°C, and 36°C. The treatment took place during the pupal stage, when young bees undergo their last major transformation in assuming an adult body.

The temperature didn't affect how many of the bees matured nor did it influence their adult appearance, the researchers report.

Tautz and his colleagues tested learning in the bees by giving them whiffs of a citronella smell along with a treat of sugar water. A minute later, the bees from the warmest pupahood were most likely to associate the scent cue with the treat and stick out their tonguelike proboscises in response to a puff of citronella odor. The difference between the two colder—and the warmest—pupahood bees became even more pronounced when researchers waited 10 minutes to administer the test. Such a difference in cognitive powers might affect bees' performance as foragers, the researchers speculate.

When the bees reached the age for foraging, the researchers tested five from the groups raised at 32°C and 36°C. Videotapes of these bees after visits to a source of sugar water showed that the dances of the chilled group had sloppier variations and fewer turns—all in all, sad performances.

The researchers speculate that the chill affected the bees' nervous systems during a critical phase, when it was changing to meet adult demands.

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References:

Tautz, J., et al. In press. Behavioral performance in adult honeybees is influenced by the temperature experienced during their pupal development. Proceedings of the National Academy of Sciences. Abstract.

Further Readings:

Milius, S. 2001. Senior bees up all night caring for larvae. Science News 159(April 28):263. Available at Science News.

______. 1999. Look who's dancing. Science News 155(April 3):216. Available at Science News.

For videos of a bee dance, go to NOVA Online.

Sources:

Gloria DeGrandi-Hoffman
Carl Hayden Bee Research Center
USDA Agricultural Research Service
Tucson, AZ 85719

Jürgen Tautz
Lehrstuhl für Verhaltensphysiologie und Soziobiologie
Biozentrum
Universität Würzburg
Am Hubland
D-97074 Würzburg
Germany


From Science News, Volume 163, No. 21, May 24, 2003, p. 324.