The immortal jellyfish (Turritopsis dohrnii) is a jellyfish that lives forever… or does it?
If you’re like me, you’ve probably never wondered, are jellyfish immortal? But, this is a question that two researchers began asking themselves after an unexpected discovery in the 1980s.
Defying everything that researchers thought they knew to be true, adult immortal jellyfish can revert to their juvenile stage when facing stress or threats. In this way, immortal jellyfish may truly live forever… if they don’t become another animal’s snack.
What Is The Immortal Jellyfish?
Can jellyfish live forever?
The Discovery
Researchers discovered the immortal jelly (Turritopsis dohrnii) in the Mediterranean in 1883, although researchers didn’t know their immortal nature. It wasn’t until the 1980s that researchers discovered that unique ability.
Two students, Christian Sommer and Giorgio Bavestrella, collected immortal jellyfish polyps for research. After checking their collection one day, it surprised them to find new polyps. They didn’t expect to see offspring until after the original polyps had matured.
Continuing their observations, Sommer and Bavestrella noticed that, when stressed, the jellyfish fell to the bottom of their jar to become polyps
What Immortal Jellyfish Look Like
Immortal jellyfish are incredibly tiny, reaching a size no bigger than 0.19 in (0.5 cm) in length. Their bell (body) is transparent and you can see their bright red stomach within. At the bottom of the bell, an immortal jellyfish has many tentacles.
The bodies of immortal jellyfish are quite variable depending on where they live. Immortals living in Panama and other tropical regions have just eight tentacles. Those living in the colder waters of the Mediterranean and Japan may have over 24 tentacles.
- Common Names: Immortal Jellyfish, Eternal Jellyfish
- Immortal Jellyfish Scientific Name: Turritopsis dohrnii
- Origin: Mediterranean Sea
- Immortal Jellyfish Size: 0.19 in (0.5 cm)
- Immortal Jellyfish Lifespan: Forever (theoretically)
Immortal Jellyfish Habitat
Immortal jellyfish likely originated in the Mediterranean Sea. Today, we see immortal jellyfish in oceans all around the world.
They are excellent “hitchhikers”, attaching themselves to ships to travel long distances. It’s also likely that they get sucked into the ships with ballast water. Such an experience would kill most jellyfish. Thanks to the immortal jellyfish’s regenerative properties, they can survive until the ship expels them back into the water.
How Does The Immortal Jellyfish Live Forever?
Rather than dying, an old immortal jellyfish reverts to its polyp stage, effectively restarting its life cycle. It becomes a polyp again in a process that we call “transdifferentiation”.
Reverting From Adult To Polyp
The cells and organs are different between polyps and medusa. Some cells and organs are present in the polyp, but not the medusa, and vice versa. Transdifferentiation reprogrammes the cells of the medusa to become polyp cells again, allowing the jellyfish to regrow.
The jellyfish regenerates and repurposes its cells. The jellyfish reverts to its younger polyp stage and begins growing into its adult (medusa) form again.
In short, a juvenile grows into an adult, reverts to a juvenile, and grows into an adult again. Their life cycle can continue over and over.
But that’s not all.
Are Regenerated Jellies The Same Organism?
A reverted polyp doesn’t just begin growing into a medusa again. The cells have changed enough that they’ve created an almost entirely new being.
Because the cells have changed so much, researchers question if immortal jellyfish are really immortal at all. Can we consider an organism to be the same creature if it has replaced all its cells?
Although all the cells have been replaced, the genes are still the same. So, for now, researchers conclude it is the same organism, and immortal jellyfish really are “immortal”.
Immortal Jellyfish Have Protective Genes
A comparison between the immortal jellyfish (Turritopsis dohrnii) and the crimson jelly (Turritopsis rubra) shows that immortal jellyfish have double the amount of protective genes that crimson jellies have. These genes offer protection to the immortal jellyfish’s DNA and repair damage. These genes also allow the immortal jellyfish to create more restorative proteins.
Research also shows that mutations in the immortal jellyfish’s genes preserve “telomeres”, the part of the DNA that protects chromosomes. Telomeres usually shorten as an animal ages, but not in an immortal jellyfish.
Can Immortal Jellyfish Die?
Immortal jellyfish can restart their lives, but that doesn’t mean they can’t die. Their small size makes them easy prey for several species, including sea slugs, crustaceans, fish, and sea turtles.
An immortal jellyfish will only revert to a polyp if it’s experienced harm or threat. Instances of this include starvation, changing water conditions, or injury.
In theory, immortal jellyfish can reprogram themselves over and over so that they never die, but the science isn’t perfect.
The Immortal Jellyfish (Turritopsis dohrnii) Life Cycle
Like most animals, jellyfish produce eggs and sperm. Jellyfish release the eggs and sperm into the water column, where the eggs become fertilized.
When jellyfish are “born”, their lives begin as a planula, a type of larva. The larva forms from a fertilized egg. The planula swims until it finds a suitable place to settle on the seafloor.
Once the larva finds a place on the seafloor, it grows into a large colony of polyps. As they age, the polyps transform into free-swimming medusa, or jellyfish. The medusa are all genetically identical and become adults in just a few weeks.
As an adult, immortal jellyfish only reach a length of about 0.19 in (0.5 cm), this is smaller than the nail on your pinky finger.
After this, other jellyfish species eventually die because of old age or predation.
Immortal jellyfish are still susceptible to predation, but they won’t die of old age. Immortal jellyfish revert to their polyp stage once they become too old, or experience starvation or damage.
How Does An Immortal Jellyfish Become Young Again?
What exactly happens when an immortal jellyfish experiences damage or some other threat? London’s Natural History Museum describes it this way:
“When the medusa of this species is physically damaged or experiences stresses such as starvation, instead of dying it shrinks in on itself, reabsorbing its tentacles and losing the ability to swim. It then settles on the seafloor as a blob-like cyst.”
The blob then transforms into a polyp over the next 24-36 hours. The polyps continue to mature as they did previously, and eventually, adult medusa come away.
Immortal Jellyfish May Help Humans
Researchers aren’t expecting to unlock the key to immortality by studying immortal jellyfish. But, they believe that immortal jellyfish may have the key to fighting disease.
The American Museum of Natural History describes researcher’s hope for the future:
“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.”
Conclusion
The immortal jellyfish is a jellyfish that can live forever… theoretically.
Immortal jellyfish can still die if they become prey to other animals. Their bodies are miniscule, so they are easy prey for a variety of hungry creatures.
Still, their specialized cells make it possible for them to revert to their juvenile stage when they experience damage or stress. If they avoid predation, they have the potential to live forever.
Making this discovery opens up a world of possibilities, not only for better understanding the ocean, but in helping fight disease.
What other amazing things might the ocean reveal to us one day?
FAQs
No, the immortal jellyfish is the only animal that we know of that is “immortal”. All other jellyfish age and die normally.
All jellyfish share the same life cycle. They begin as larvae, become polyps, and transform into medusa. The difference is, while other jellyfish species eventually die, the immortal jellyfish becomes young again and continues living.
Immortal jellyfish can potentially live forever, so researchers do not consider them “endangered”.
It’s exceptionally difficult to study immortal jellyfish, so the population trend is currently unknown.
Both jellyfish and octopuses have round bodies with tentacles or arms. But, just because they look similar doesn’t mean they are relatives.
Octopuses are cephalopods, a type of animal who has two eyes, a mantle, a funnel (siphon), and eight or more arms. Jellyfish are cnidarians, a type of animal who has “nematocysts”, or stinging cells.
According to Dr. Cheryl Ames of the Smithsonian National Museum of Natural History, an octopus’s tentacles are thick meat that you can eat. A jellyfish’s tentacles are more like thin, hollow straws.
Another significant difference is that octopuses have three layers of tissues while jellyfish only have two. Octopuses have two openings for their digestive tract, while jellyfish only have one. Probably most important of all, octopuses have brains, while jellyfish don’t.
