Dopamine Turns Worker Ants into Warrior Queens (VIDEO)

One species of ant looks like a worker on the outside, but a rise in dopamine levels triggers dramatic physical changes without affecting their DNA, and results in warrior-like ritualized fighting behavior, according to a recent study published in The Journal of Experimental Biology.

Researchers from North Carolina State University, Arizona State University and the US Department of Agriculture studied Indian jumping ants (Harpegnathos saltator), which can undergo significant changes in physiology. Their brains shrink by 25 percent, their ovaries expand to fill their abdomens and their life expectancy jumps from months to years.

Surprisingly, female ants are the ones who demonstrate this macho behavior. When an H. saltator colony's queen dies, females fight with each other for power. These battles can be intense, but rarely are any ants injured.

Ultimately, a group of about 12 workers will establish dominance and become a band of worker queens or "gamergates." But the reasoning behind their subsequent physical changes was unknown.

"We wanted to know what's responsible for these physical changes," lead author Dr. Clint Penick said in a statement. "The answer appears to be dopamine. We found that gamergates have dopamine levels two to three times higher than other workers."

So they took some workers from a colony (Colony A) and separated them from their gamergates. These workers formed their own colony (Colony B) and began fighting to establish dominance.

When Colony B ants got the upper hand, they were removed. Researchers found that these dominant ants had begun to produce elevated levels of dopamine - more than other workers, though less than full-fledged gamergates.

When the dominant workers were placed back into their original colony (Colony A), the other workers realized the threat and held down the dominant ants so they couldn't move.

Within 24 hours, the dopamine levels in the dominant workers had dropped back to normal.

"This tells us that the very act of winning these ritual battles increases dopamine levels in H. saltator, which ultimately leads to the physical changes we see in gamergates," Penick concluded. "Similarly, losing these fights pushes dopamine levels down."

The findings may offer insight into the behavior of various social insect species, Penick said.

"Policing behavior occurs in wasps and other ant species, and this study shows just how that behavior can regulate hormone levels to affect physiology and ensure that workers don't reproduce," he explained.