Worker bees have power to pick their queen
Although every bumblebee colony has a queen, the process of becoming that queen bee can be a little more democratic than monarchical. Worker bees appear to select which baby will one day be queen, according to a new study published in the journal Insect biochemistry and molecular biology.
The key to this selection process lies in the juvenile hormone. This hormone in insects is responsible for their development, molting and eventual reproduction. When the team gave the workers juvenile hormone, they passed it on to all the larvae in the colony through food. The more juvenile hormones the larvae received, the more likely they were to become queens.
According to the team, this is the first study to show that bumblebee caste is determined by workers and changes our understanding of bee colony dynamics. Instead of a top-down hierarchy, the colony appears to be a more decentralized system, in which caregivers and workers can change the future of baby bees.
Less like mean girls?
Understanding the fate of bee larvae is essential to understanding their social behavior. Their entire system is based on a division of reproductive labor: some females will breed while others help.
“As all of these females share the same DNA, this is a striking example of how the same genotype can produce very different forms,” Etya Amsalem, study co-author and entomologist at Penn State, said in a statement. “It’s also a practical question since bumblebees are important for pollination, so knowing how to produce queens could improve breeding and commercial management.”
In addition to their different social roles, queens and workers are also very different physically. Bumblebee queens are larger, live longer and reproduce. Worker bees are smaller and do not reproduce or live as long.
While it was clear that hormones were involved in how workers queen, the exact mechanisms behind them were more vague.
“A single female egg in bumblebees contains the blueprint for two completely different life paths: the giant, reproductive queen or the small, sterile worker,” added study co-author and postdoctoral researcher Seyed Ali Modarres Hasani. “We wanted to understand what triggers change in the female life trajectory, when it happens and who controls the process. »
A question of hormones
In the study, the team used three worker bees and a group of larvae. They applied juvenile hormone in different doses and at different times, and administered it either to workers or directly to larvae. They then tracked the movement of the hormone, measuring the mass of the larvae and recording which individuals became queens or workers.
“Each colony will produce many new queens at the end of the season,” Amsalem said. “These queens will leave the colony, mate and enter winter diapause, then each queen will start a new colony the following spring. In this sense, producing as many queens – and males – at the end of the season, is the ultimate goal of the colony.”
When juvenile hormone was applied directly to the larvae, not only did they not develop into queens, but the worker bees ended up eliminating most of these larvae.
When workers were treated with juvenile hormone, they incorporated it into the food they prepared for the larvae. These larvae then ingested the hormone and were heavier and much more likely to become queens.
“We also determined that larvae are only sensitive to this hormone on the seventh and eighth days of their development,” Hasani said. “By tracking juvenile hormone, we saw that workers transmit the hormone in the food they make from nectar and pollen.”
Development of the queen and future of the colony
These results suggest that queen production is linked to how the colony progresses through the warmer summer months until it eventually collapses in the fall.
“Bumblebee workers do not reproduce when the colony is young, but they can activate their ovaries and produce males as the colony ages, causing an increase in juvenile hormone levels,” Amsalem said. “As a result, over time, they feed the larvae more of the hormone. When enough workers do so simultaneously, usually toward the end of the season, the larvae receive high enough doses during the critical window to develop into queens.”
These findings could help improve bee colony management at the hormonal level, explaining how complex insect societies evolve and how hormonal signals interact to shape colony structure.
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