Scientists have identified brain circuits that help determine which jobs worker bees perform inside a colony. Biologists from Heinrich Heine University Düsseldorf (HHU) and the universities in Cologne and Frankfurt/Main found that they could change bee behavior by manipulating a particular gene and selectively reducing activity in certain neural circuits.
The findings, published in the scientific journal Proceedings of the National Academy of Sciences (PNAS), offer new insight into how a colony organizes its workforce without a leader assigning tasks.
How Bees Divide Work Without a Leader
Any successful community depends on its members completing the right jobs at the right time. Humans can discuss responsibilities and deliberately assign them, but a bee colony has no central planner. Even so, bees (Apis mellifera) divide their work with remarkable efficiency.
A worker bee’s responsibilities typically change as it grows older. Young workers care for the queen and developing larvae. Later, they help build and maintain the hive and defend it against threats. Only during the final stage of their lives do they leave the colony to search for food.
These behavioral changes are directed by interactions among roughly one million neurons in the bee brain. Until now, however, scientists did not understand how the nervous system produces this age-dependent progression from one task to another.
A Gene Linked to Worker Bee Behavior
Important clues emerged from earlier research by a team at HHU led by Professor Dr. Martin Beye of the Institute of Evolutionary Genetics. The scientists were studying a gene known as doublesex when they observed an unusual behavioral change.
When the gene was deactivated in older worker bees, the insects began caring for the queen again. This responsibility is normally performed only by younger bees, suggesting that doublesex plays an important role in controlling age-related work behavior.
Because the doublesex gene operates only within certain neural circuits, the discovery gave Professor Beye’s team, together with researchers from the universities in Cologne and Frankfurt/Main, a way to investigate how specific parts of the bee brain influence social behavior.
Scientists Switch Off Specific Neural Circuits
The researchers selectively silenced neurons associated with doublesex. To accomplish this, they used the gene to produce a protein that suppresses neural activity. They then activated that protein by feeding the bees a particular substance, allowing them to reduce activity only in the targeted circuits.
Once those circuits were inhibited, older workers returned to caring for the queen instead of performing the duties expected at their age.
Dr. Jana Seiler, lead author of the PNAS study, said, “The older worker bees then resumed caring for the queen, which only younger bees would do otherwise. When the circuits were not inhibited, the bees exhibited their normal, age-dependent behavior. In this way, we were able to control which tasks the worker bees performed.”
Neural Communication May Organize the Hive
The results indicate that task organization within a bee colony has a neural foundation. When activity in particular areas of the brain is reduced, other neural circuits may become active and trigger a different set of behaviors.
The findings provide early evidence that communication between neural circuits helps determine whether a worker bee nurses the queen, builds or guards the hive, or searches for food.
Professor Beye concludes, “The ability to control the social behavior of bees offers us new opportunities to explore the fundamentals of innate behavioral diversity and social cooperation. The solution to the secret of how bees and other animals cooperate so well without a blueprint for work is likely hidden in the brain’s neural circuits.”