Immortal Jellyfish May Hold Clues to Human Ageing

The tiny, translucent jellyfish Turritopsis dohrnii can reverse its life cycle and become young again. Scientists think its cellular tricks could one day matter for people. Maria Miglietta, a marine biologist at Texas A&M University at Galveston, has cut, boiled and starved the animal, overloaded its tanks with salt, and placed it in fresh water. Again and again, the jellyfish appeared to evade death.

Under stress, the jellyfish stop moving and sink to the bottom of their tank. Then they transform into balls of cells, nothing like the tentacled, umbrella-shaped adult form known as the medusa. Within one to three days, a polyp, an early jellyfish life stage, buds from the ball and grows into a colony. That colony eventually produces new medusae. “From one jellyfish that doesn’t die, then you get this colony that can form hundreds more,” Miglietta said. Each new jellyfish can, in principle, rejuvenate in the same way.

The Discovery Story

Scientists first reported the regenerative ability in 1992, almost by accident. An Italian scientist who kept the animals in a laboratory forgot to feed them over a weekend. He expected to find them dead, but returned to discover new polyps in the container, Miglietta said. Stefano Piraino, a biologist at Italy’s University of Salento, then studied how rejuvenation might work. He found that certain tissues in the medusa undergo “transdifferentiation” during the process, reverting to a stem-cell-like state before specialising into other cell types. “Adult cells become ‘undifferentiated’ and become something else that is needed to form the polyp,” Miglietta said. She formerly worked in Piraino’s lab.

The species has earned the nickname “immortal jellyfish.” As far as scientists know, it’s unique in the animal kingdom. Some lizards, worms and amphibians can regrow lost or injured body parts. But none are known to revert an adult body to an early life stage. The jellyfish suggests ageing and mortality aren’t necessarily biological inevitabilities, though scientists can’t rule out that it eventually dies naturally.

The Genetic Search

This is where the research gets interesting for anyone worried about the cost of ageing. A 2022 study compared Turritopsis dohrnii genes with those of a related species not known to rejuvenate. Victor Quesada, a molecular biologist and bioinformatician at the University of Oviedo in Spain, cautioned that it’s hard to know whether the related species truly lacks the ability, because many jellyfish are understudied. Even so, Turritopsis dohrnii had more copies of genes that produce proteins to repair mutations and other DNA damage accumulating with age. It also carried more copies of genes that help maintain telomeres, the protective caps at the ends of DNA strands that normally shorten over time. Quesada said greater telomere maintenance could be one factor in its longevity.

Miglietta has compared genes activated at different life stages and studied those active only during the ball-like cyst stage. Her research in 2019 and 2021 found increased activity in genes with unknown functions, alongside genes involved in DNA repair and telomere maintenance. In a separate preliminary study, Miglietta found some overlap between genes overactivated during the cyst stage and genes linked to human longevity. That overlap hints at possible shared pathways between the two species.

Limits of the Promise

Nobody should expect a clinic to start selling jellyfish-derived youth treatments. Michael Koldobskiy, a pediatric oncologist and physician-scientist at Johns Hopkins, said turning elderly people into babies is science fiction. “The holy grail of this kind of thing, I think, would be regenerative biology: trying to reverse ageing-related degeneration or degradation,” he said. “We’re a long way away from harnessing that for human benefit.” He added that “we’re not going to shrink down to an embryo again and restart,” but said that “at the organ and tissue level, I think it’s very much a possibility.”

Koldobskiy is collaborating with Miglietta to identify the molecular switch that controls the process and test whether it can be induced in human cells. Scientists have managed rejuvenation-like processes in mammalian cells, but applying them to human tissue has proved difficult. If it comes, the payoff could include healing wounds or tissue damaged by strokes or heart attacks, and reversing damage linked to age-related vision loss or Alzheimer’s disease.

The animal itself is fragile. Some specimens in Miglietta’s laboratory appear unable to rejuvenate, and those that can may eventually reach a limit and die of old age. The species is hard to keep in captivity and seems to need specific conditions. In the wild, shifting plankton supplies, predators and algae that smother colonies may kill it. Maria Pascual-Torner of Spain’s Institute of Marine Sciences, who worked on the 2022 study with Quesada, put it plainly: “Although it has the ability to rejuvenate and, theoretically, not die from ageing, it is at the same time an extremely vulnerable organism.” She added: “The immortal jellyfish also reminds us that life and death are inseparable parts of the same reality.”

Why This Matters: Ageing-related disease carries a heavy fiscal load on health systems across Europe. Any future therapy that repairs tissue rather than merely managing symptoms would change that equation. For now, the jellyfish research remains basic science, with a long road between a marine animal’s genome and a treatment that a national health service could afford to provide. Governments and funders should weigh the early promise against the realities of cost and timeline, and resist treating laboratory findings as ready solutions. Investment in fundamental biology is worth making, but it should be disciplined, transparent and judged on results rather than hype.