A tiny sea creature known as the immortal jellyfish appears to cheat death by reversing its own aging process, turning itself back into an earlier life stage whenever it is injured, starving, or under stress, researchers say.
The species, scientifically named Turritopsis dohrnii, is the only jellyfish confirmed to be capable of repeating this cycle, according to marine biologists who have studied it for decades. Most jellyfish begin as eggs, grow into free-swimming larvae, settle into stationary polyps, and mature into adult jellyfish, called medusae. Like most animals, they eventually die.
Turritopsis breaks that pattern. When damaged or stressed, its body shrinks, its tentacles pull inward, and it sinks to the seafloor as a small blob. Within one to two days, the blob develops into a new polyp, restarting the life cycle from an earlier point. Scientists call this process transdifferentiation, in which the jellyfish’s specialized cells reorganize themselves into the different cells needed to build a polyp.
How the “immortal jellyfish” cheats death under extreme conditions
Maria Pia Miglietta, a marine biologist at Texas A&M University, said the species can withstand extreme heat, physical injury, starvation, and even chemical exposure without dying. Rather than breaking down, she said, it reverses course and starts over.
🚨: The immortal jellyfish, known as Turritopsis dohrnii, can hit the reset button on its life. When stressed or aging, it shrinks back into a baby polyp stage and starts over
Biologically immortal. pic.twitter.com/diyIImslvW
— All day Astronomy (@forallcurious) May 26, 2026
Scientists first described the species in 1883, but its unusual ability went unnoticed until the 1980s, when students Christian Sommer and Giorgio Bavestrello observed jellyfish in a lab reverting to polyps instead of dying, without going through the normal reproductive steps.
Researchers say the immortal jellyfish, despite its ability to cheat death by rejuvenating itself, is not indestructible and still falls prey to fish, turtles, sea slugs, and crustaceans.
Miranda Lowe, a curator at the Natural History Museum in London, noted that the species is difficult to study because tracking it over time requires years of observation and nearly ideal conditions.
Decades-long study traces species’ journey across world’s oceans
Japanese researcher Shin Kubota has raised colonies of the jellyfish since the 1990s. Over one two-year stretch, he recorded colonies reverting to a younger form as many as ten times.
Scientists believe the species originated in the Mediterranean Sea and has since spread to oceans worldwide, likely carried in ship ballast water.
Tentacle counts vary by region, with populations near Panama typically having eight and those in cooler waters, including Japan and the Mediterranean, having 24 or more. Researchers are not sure why this is.
Lisa-ann Gershwin, a biologist who studies jellyfish, said the species speaks to a fascination with immortality that has existed throughout human history and its tiny size makes its abilities even more remarkable.
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