A clever molecular trick extends the lives of these ant queens

For some ant queens, the secret to long life might be a self-produced insulin blocker.

Ant queens are famously long-lived, even though they shouldn’t be. Generally, animals that put lots of energy into reproduction sacrifice some time off their life. But ant queens produce millions of eggs and live an extraordinarily long time compared with worker ants that don’t reproduce.

Now, researchers have shown how one ant species pulls off this anti-aging feat. When queens and wannabe queens of the species Harpegnathos saltator gear up to reproduce, a part of what’s called the insulin signaling pathway gets blocked, slowing aging, the researchers report in the Sept. 2 Science. That molecular pathway has long been implicated in aging in mammals, including humans.

“There’s been a need to understand why queens, or reproductives, in social insects can live for so amazingly long,” says Marc Tatar, a biologist at Brown University in Providence, R.I., who was not involved with the study. Some ant species have queens that survive 30 times as long as their workers. Other social insects such as bees and termites also have long-lived queens.

In a rare behavior for ants, when a queen H. saltator dies, some female workers begin competing in duels for the chance to replace her (SN: 1/17/14). These hopeful royals develop ovaries, start laying eggs and transition into queenlike forms called gamergates. When a worker transitions to a gamergate, her life span becomes five times as long as it was. But if she doesn’t end up becoming queen and reverts back to a worker, her life span shortens again.

The researchers exploited this behavior to investigate the molecular underpinnings of anti-aging in these ants. H. saltator gamergates, it turns out, extend their life spans by taking advantage of a split in the insulin signaling pathway, the chain of chemical reactions that drive insulin’s effects on the body. One branch of this pathway is involved with reproduction, while the other is implicated in aging.

“Insulin comes with our life — [after] we eat, we have high insulin,” says Hua Yan, a biologist at the University of Florida in Gainesville. “But a constant high level of insulin is bad for longevity.”

Examining patterns of gene activity, Yan and colleagues found that gamergates have more active insulin genes than regular worker ants and, as a result, have increased metabolic activity and ovary development. But the secret sauce protecting the ants from the insulin’s aging effects appears to be a molecule called Imp-L2, which blocks the branch of the insulin pathway linked to aging, experiments showed. The branch involved in reproduction, however, remains active.

“What we don’t understand is how Imp-L2 can act on one aspect of the pathway and not on the other,” says study coauthor Claude Desplan, a developmental biologist at New York University.

These results represent a leap forward in our understanding of extreme social insect longevity, the researchers say, while also showcasing an anti-aging evolutionary adaptation that hasn’t been seen in the wild before.