In oceans across the globe, a tiny jellyfish species—smaller than the nail on your pinky finger—displays remarkable death-defying abilities. After reaching sexual maturity, this jellyfish can revert to its juvenile stage and mature again—a feat that would be akin to a butterfly turning back into a caterpillar, then metamorphosing again into a butterfly.
The deep-sea creature’s life cycle could theoretically be repeated indefinitely, earning this species, called Turritopsis dohrnii, a nickname: the “immortal jellyfish.”
“We’ve known about this species being able to do a little evolutionary trickery for maybe 15–20 years,” Monty Graham, a jellyfish expert and director of the Florida Institute of Oceanography, tells Reuters’ Julie Steenhuysen. But in a new study, researchers looked to the animal’s genes to find out how it achieves this exceptional feat.
In the paper published in the Proceedings of the National Academy of Sciences, a team of researchers from the University of Oviedo in Spain mapped the genetic sequence of the jellyfish, revealing “key molecular mechanisms behind rejuvenation of T. dohrnii,” the scientists write. Researchers say their work could help promote health for aging humans.
Like a typical jellyfish, the “immortal” T. dohrnii begins its life as a free-floating larva. It finds a hard surface to attach to, such as a rock or shell, and matures into a branching, plant-like polyp. From there, multiple young jellyfish bud off from the polyp and turn into medusae, or adults.
But here’s the difference: When an adult “immortal jellyfish” is damaged or stressed, instead of dying, it absorbs its own tentacles and becomes a blob that settles to the sea floor, per London's Natural History Museum. Over the next day and a half, this blob becomes a new polyp, which can then form more medusae. So, though T. dohrnii may succumb to a predator, it can thwart dying of old age.
The new study compared T. dohrnii to T. rubra, a related jellyfish species that ages normally. Compared to its relative, researchers found, the “immortal jellyfish” has double the amount of genes that repair and protect DNA, writes Jason P. Dinh for New Scientist. This allows T. dohrnii to produce more restorative proteins.
The authors also found differences in several other genes, including those associated with replication and stem cell population. “Immortal jellyfish” had mutations that preserved telomeres, or DNA sequences that protect the end of a chromosome and typically shorten with age, New Scientist writes. These differences may be key to the jellyfish’s immortality.
“The most interesting thing is that it’s not a single molecular pathway… It is a combination of many of them,” Jan Karlseder, a molecular biologist and director of the Glenn Center for Biology of Aging Research at the Salk Institute, tells the Wall Street Journal’s Ginger Adams Otis and Alyssa Lukpat. “If we want to look for an extension of healthspan, we cannot just focus on one pathway. That will not be sufficient. We need to look at many of them and how they synergize.”
Researchers say the finding could help humans—but not in the exact same way. “It’s a mistake to think we will have immortality like this jellyfish, because we are not jellyfish,” co-author and marine biologist Maria Pascual Torner tells the Wall Street Journal.
However, the authors hope their research could help “find better answers to the many diseases associated with aging that overwhelm us today,” says co-author Carlos López-Otín, a biochemist and molecular biologist at the University of Oviedo, in a statement. Better understanding these jellyfish genes might inspire regenerative medicines for humans, per New Scientist.
More research is needed to further understand this jellyfish’s aging process. For example, it’s still unclear whether the new adult medusae are the same individuals they were before reverting back to their polyp stage, writes Lonnie Lee Hood for Futurism.
“It’s one of those papers that I do think will open up a door to a new line of study that’s worth pursuing,” Graham, who was not involved in the research, tells Reuters.