The immortal jellyfish (Turritopsis dohrnii) is a specific species of jellyfish that has the ability to revert back to its youthful, immature state after it reaches maturity. It’s a very small species that reaches a diameter of about 0.18 inches. It’s found in the Mediterranean Sea and in the waters around Japan.
This creature gets its nickname from its ability to undergo a process called transdifferentiation. This allows it to revert back into a polyp and start its life cycle over again.
Wait, seriously? There’s a jellyfish that can reincarnate itself and live forever?
Ehhh, kind of. But jellyfish don’t live their lives by the same rules that we do. Their brains and community structures don’t operate in the same ways. It’s not like their memories live on forever (that we know of).
The process of transdifferentiation in this jellyfish acts kind of like a reset button.
Turritopsis dohrnii begins life as a fertilized egg that then hatches a larva (or planula). According to the American Museum of Natural History (cited below):
“A planula swims at first, then settles on the sea floor and grows into a cylindrical colony of polyps. These ultimately spawn free-swimming, genetically identical medusae—the animals we recognize as jellyfish—which grow to adulthood in a matter of weeks.”
Anyway, during the medusa stage, the jellyfish will reproduce sexually, releasing eggs and sperm into the water. There, they will fertilize and develop into the next stage, known as a polyp. Some jellyfish species will alternate between a medusa stage and a polyp stage in their life cycle, while others will only have a medusa stage.
Here’s the key: Once the medusa reaches maturity, it can reproduce and then die, but the immortal jellyfish is able to undergo transdifferentiation, reverting back to its polyp stage, and starting the life cycle again.
The AMNH explains:
“The cellular mechanism behind it—a rare process known as transdifferentiation—is of particular interest to scientists for its potential applications in medicine. By undergoing transdifferentiation, an adult cell, one that is specialized for a particular tissue, can become an entirely different type of specialized cell. It’s an efficient way of cell recycling and an important area of study in stem cell research that could help scientists replace cells that have been damaged by disease.”
Why isn’t this a bigger deal? Can we study jellyfish to become immortal?
Undoubtedly, some billionaire has a tank full of immortal jellyfish and a geneticist at hand to try to discover that particular secret of life. But it’s important to keep in mind – again – just how different a jellyfish’s life cycle is from our own. And there’s A LOT we don’t understand about underwater creatures, which may actually hold a lot of cool secrets about life, the universe, and everything.
So, it’s important to note that it is not completely understood how or why this process of transdifferentiation occurs. It’s only unclear if these jellyfish truly can live forever or not. (I mean, what is “forever” anyway, and how do humans even measure it?)
But it is a pretty cool trick.
The immortal jellyfish is also known to be a hardy species. It can survive in a wide range of conditions, allowing it to spread and colonize new areas. Of course, there’s a downside to being hearty and potentially immortal. It’s also known to be an invasive species in many parts of the world. That means it can cause serious damage to native ecosystems. In that sense, its potential immortality is a bit of a nuisance.
In any case, the immortal jellyfish is a fascinating creature that scientists are still trying to understand.
Now, you may have noticed another fun fact which is that a mature jellyfish is often referred to as a “medusa.” The medusa is the adult, sexually reproducing stage of a jellyfish’s life cycle. The name “medusa” is taken from Greek mythology, and the jellyfish’s trailing tentacles are thought to resemble the head of Medusa.— WTF fun facts
Source: The “Immortal” Jellyfish That Resets When Damaged — American Museum of Natural History