Bee Aggression Stems from Brain Metabolism

Bee aggression can reportedly be cranked up a notch when simply interfering with a basic metabolic pathway in the insect brain, according to researchers.

The study, published in the journal Proceedings of the National Academy of Sciences, shows a direct, causal link between brain metabolism - how the brain generates the energy it needs to function - and aggression among fruit flies and honeybees.

But what the research team found was that after a honeybee confronted an intruder some metabolic genes were suppressed. These genes play a key role in the most efficient type of energy generation in cells, a process called oxidative phosphorylation.

"It was a counterintuitive finding because these genes were down-regulated," lead author Gene Robinson, an entomology professor at the University of Illinois, said in a statement. "You tend to think of aggression as requiring more energy, not less."

To delve further into this association, researchers used drugs to suppress key steps in oxidative phosphorylation in the bees' brains. What resulted was that drugged bees exhibited more aggression in a dose-responsive manner, according to Robinson. But, the drugs had no effect on chronically stressed bees.

"Something about chronic stress changed their response to the drug, which is a fascinating finding in and of itself," Robinson explained. "We want to know just how this experience gets under their skin to affect their brain."

In separate experiments, postdoctoral researcher Hongmei Li-Byarlay and undergraduate student Jonathan Massey found that reduced oxidative phosphorylation in fruit flies also increased aggression. And advanced fly genetics revealed the surprising finding that this response only occurred if oxidative phosphorylation was reduced in neurons, but not in neighboring glial cells.

Robinson explains that aggression is an immediate response among insects - and all animals for that matter - occurring within seconds of a threat. But changes in brain metabolism take longer to catch up to this quick reaction time. Such changes likely make individuals more vigilant to subsequent threats.

"This makes good sense in an ecological sense," Robinson added, "because threats often come in bunches."