Jumping ants fight for dominance after their queen dies

A study from New York University describes behavioral and physiological changes that occur among some ants after the death of their queen. A species of jumping ants found in India, Harpegnathos saltator, engages in dueling tournaments to establish new leadership.

The ants strike each other with their antennae in a series of battles that can drag out for weeks. But the new study found that even if the sparring matches stretch out for months, the winner can be determined in a matter of just three days based on changes in behavior and gene expression.

“Despite prolonged social upheaval in ant colonies following the loss of the queen, the winners of these dueling tournaments are rapidly determined,” said study co-author Professor Claude Desplan. 

“Our findings may provide clues on adaptability in reproduction and aging, given that the workers who win the duel, or ‘pseudoqueens,’ gain the ability to lay eggs and live much longer than the average worker ant. This suggests that changes in the environment are able to dramatically affect the structure of a society.”

Ant societies have a division of labor in which the queen is in charge of reproduction and workers are responsible for maintaining the colony. The workers take on daily tasks like cleaning, caring for the young, hunting for food, and defending the nest.

In many cases, the entire ant colony collapses and dies after the queen due to a lack of reproduction. However, Indian jumping ants go through a period of social unrest and “caste switching” after queen loss. 

While the queen is still alive, she secretes pheromones that prevent female workers from laying eggs. When the queen dies, the workers sense the lack of pheromones and begin fighting each other for social dominance.

“Most workers quickly abandon the tournament while a few workers continue the dueling for months and become gamergates (pseudo queens),” explained the researchers.

The ants that stick it out in battle and become pseudo queens acquire new behaviors, and their life expectancy dramatically increases from seven months to four years. The pseudo queens begin laying eggs, which allows the colony to survive.

The NYU team analyzed changes in social behavior and accompanying changes in gene expression during the early stages of the transition from worker bee to pseudo queen.

The study revealed that, as early as three days after Indian jumping ants begin dueling, the winners can be accurately predicted solely based on their behavior. 

The workers who ultimately became pseudo queens were found to engage in about twice as much dueling activity within the first five days. Meanwhile, the bees who dueled less gradually went back to cleaning, hunting, and other worker bee tasks.

According to study co-author Professor Danny Reinberg, both behavioral and molecular data – especially changes in gene expression in the brain – show that new pseudo queens are quickly determined after a colony’s social structure has been disrupted by the loss of the queen.

“Despite the fact that dueling tournaments last for several weeks, we were able to anticipate which ants would become pseudo queens in only three days,” said study co-lead author Comzit Opachaloemphan.

The experts found that the first genes to respond to the loss of the queen were in the brain, and that the absence of the queen pheromones triggers a series of behavioral and physiological changes. Ultimately, the brain is the driving force behind the dueling and early caste determination in the ants, with other tissues taking cues from the brain.

“We show that molecular changes in the brain serve as earliest caste predictors compared with other tissues,” wrote the researchers. “Thus, behavioral and molecular data indicate that despite the prolonged social upheaval, the gamergate fate is rapidly established, suggesting a robust re-establishment of social structure.”

The study is published in the journal Genes & Development.

—

By Chrissy Sexton, Earth.com Staff Writer