For centuries, humans have searched for the fountain of youth. We’ve tried everything—miracle creams, green smoothies, cryotherapy, and even freezing ourselves for future scientists to figure out. But as it turns out, nature might have beaten us to it. The secret? A tiny, see-through jellyfish that drifts through the ocean like a living time machine.
Meet Mnemiopsis Leidyi, a comb jellyfish with an incredible ability. Scientists have just discovered that this bizarre little creature can reverse its own aging process, turning back the biological clock when under stress.
A Happy Accident
Researchers in the Michael Sars Centre at the University of Bergen were observing comb jellyfish in a lab when they noticed something strange. Instead of growing older as expected, the jellyfish suddenly reverted to a larval stage, resetting its biological clock. At first, the researchers thought it was a mistake. But after repeating the experiment, they confirmed what seemed impossible: the jellyfish wasn’t deteriorating—it was rejuvenating itself.
Dr. Joan Soto-Angel, a lead researcher on the study, was stunned: "Witnessing how they slowly transition to a typical cydippid larva as if they were going back in time, was simply fascinating."
This finding challenges existing knowledge about animal development and could open new research avenues into life cycle plasticity and rejuvenation. Until now, only one species, the "immortal jellyfish" (Turritopsis dohrnii), was known to do this.
Above: Atlantic comb jelly (Mnemiopsis leidyi). Image courtesy of Gerald Corsi via Getty Images.
How Do They Do It?
In most animals, aging is a one-way journey: cells break down, lose function, and accumulate damage over time. But Mnemiopsis leidyi seems to have found a loophole. Instead of simply repairing itself, its body reprograms its cells, reverting them to an earlier state. The study highlights that this happens through transdifferentiation, a process in which cells change from one type to another. Instead of just healing, mature Mnemiopsis leidyi individuals can revert from their lobate adult form to an earlier cydippid stage. This reverse development includes the reappearance of larval structures like tentacles, not just regressing, but completely reorganizing the organism's body plan.
Unlike standard regeneration, which repairs tissue by replacing damaged cells, transdifferentiation repurposes existing cells, allowing the jellyfish to restructure its entire body into an earlier stage of development. Scientists have seen transdifferentiation in some amphibians, but never before at this scale in a ctenophore.
Life Cycle Evolution
As exciting as this discovery is, the obvious next question is: can we do this too? In the greater context of regenerative medicine, the findings presented by Dr. Joan J. Soto-Angel demonstrate the possible application of transdifferentiation principles to human cells, particularly in healing damaged tissues and regenerating organs. By understanding how Mnemiopsis leidyi repurposes its cells, we may be able to develop new treatments for injuries that go beyond traditional stem cell therapy.
Perhaps the most exciting application is in neurodegenerative disease treatment. Diseases like Alzheimer’s and Parkinson’s occur through the deterioration of brain cells. Harnessing the jellyfish’s ability to reset its cellular structures, researchers may be able to restore neurons and reverse the effects of these conditions. However, more work is needed to make full use of this discovery. Human cells are far more complex than those of jellyfish, and even if we uncover the exact mechanisms behind Mnemiopsis leidyi’s abilities, translating them to human biology will require closer inspection.
The Hunt for Other Time Travelers
Scientists are now turning their attention to other marine animals—from deep-sea creatures that endure extreme environments to mollusks and crustaceans that show signs of cellular resilience. While Mnemiopsis leidyi doesn’t have the answer to eternal youth, it has already challenged the way we think about biology. Life might not move in only one direction. And somewhere, floating beneath the ocean, more species may be waiting to teach us how to bend time.
Written by Tara Chaudhary, this article was selected as a winner of our 2025 High School Science Communication Challenge. From Plainview, New York, Chaudhary is a student at Plainview-Old Bethpage John F. Kennedy High School.