Insulin-blocking protein may be the secret to queen ants’ long lives

A protein that suppresses the production of insulin could be behind the unusually long lives of queens in a species of Indian jumping ant (Harpegnathos saltator). The discovery provides new insight into ageing, with lessons that could apply to the longevity of more complex species.

H. saltator queens live nearly nine times as long as female worker ants, surviving for around five years, while workers usually die after around seven months. Queens birth all the ants in a colony. Reproduction is energy-intensive and leads to an increase in levels of insulin, a hormone that helps break down food into energy. In most animals, an abundance of insulin is linked to a shorter lifespan, but Indian jumping ants break this rule.

“It’s contradictory to everything we know about the link between reproduction and ageing,” says Claude Desplan at New York University.

He and his colleagues analysed insulin production in female Indian jumping ants. After a queen H. saltator ant dies naturally, a handful of previously infertile female worker ants vie for her position. As these “pseudoqueens” start producing eggs, their lifespan increases from months to years.

Desplan and his colleagues plucked queen ants from their colonies to create pseudoqueens, which then churned out significantly more insulin than the female worker ants in the colony.

Female H. saltator ants have two insulin signalling pathways: one that drives egg production, called MAPK, and one that plays a role in ageing, called AKT. Usually, the hormone travels both routes, but when the ants were promoted to pseudoqueens they began producing a protein called Imp-L2 that blocks the pathway that leads to ageing while leaving the pathway for egg production open.

When they returned the pseudoqueens to a colony with a true queen, the ants reverted back to their old roles as workers and had shorter lifespans. Their insulin levels fell, and so did their production of the anti-insulin protein.

This work “pushes well beyond what we knew before about the biochemistry of insulin signalling in ants”, says Vikram Chandra at Harvard University, who wasn’t involved in the research. Chandra says he would still like to see if blocking the AKT pathway extends the lives of worker ants but acknowledges such a study would take years because of the species’ lifespan. “Without doing that, it’s very hard to know whether this actually matters for lifespan,” he says.

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