theatlantic | Deep in the forests of Germany, nestled neatly into the hollowed-out shells of acorns, live a smattering of ants who have stumbled upon a fountain of youth. They are born workers, but do not do much work. Their days are spent lollygagging about the nest, where their siblings shower them with gifts of food. They seem to elude the ravages of old age, retaining a durably adolescent physique, their outer shells soft and their hue distinctively tawny. Their scent, too, seems to shift, wafting out an alluring perfume that endears them to others. While their sisters, who have nearly identical genomes, perish within months of being born, these death-defying insects live on for years and years and years.
They are Temnothorax ants, and their elixirs of life are the tapeworms that teem within their bellies—parasites that paradoxically prolong the life of their host at a strange and terrible cost.
A few such life-lengthening partnerships have been documented between microbes and insects such as wasps, beetles, and mosquitoes. But what these ants experience is more extreme than anything that’s come before, says Susanne Foitzik, an entomologist at Johannes Gutenberg University Mainz, in Germany, who studies the ants and their tapeworms. Infected Temnothorax ants live at least three times longer than their siblings, and perhaps much more, she and her colleagues report in a study published today in Royal Society Open Science. No one is yet sure when the insects’ longevity tops out, but the answer is probably in excess of a decade, approaching or even matching that of ant queens, who can survive up to 20 years.
“Some other parasites do extend life spans,” Shelley Adamo, a parasite expert at Dalhousie University, in Nova Scotia, who was not involved in the study, told me. “But not like this.”
Under typical circumstances, Temnothorax ants live as most other ants do. They reside in communities ruled by a single fertile queen attended by a legion of workers whose professional lives take a predictable trajectory. They first tend the queen’s eggs as nurses, then graduate into foraging roles that take them outside the nest. Apart from the whole freaky parasite thing, “they are pretty boring,” Foitzik told me.
Normalcy goes out the door, however, when Temnothorax larvae ingest tapeworm-egg-infested bird feces trucked in by foragers. The parasites hatch and set up permanent residence in the young ants’ abdomens, where they can access a steady stream of nutrients. In return, they offer their host an unconventional renter’s fee: an extra-long life span that Foitzik and her colleagues managed to record in real time.
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