Immortal Jellyfish

Turritopsis dohrnii

Last updated: May 27, 2024
Verified by: AZ Animals Staff
© Rebecca Schreiner/

Excellent hitchhiker on long-trip cargo ships


Immortal Jellyfish Scientific Classification

Scientific Name
Turritopsis dohrnii

Read our Complete Guide to Classification of Animals.

Immortal Jellyfish Conservation Status

Immortal Jellyfish Locations

Immortal Jellyfish Locations

Immortal Jellyfish Facts

Tiny sea creatures
Group Behavior
  • Colony
Fun Fact
Excellent hitchhiker on long-trip cargo ships
Estimated Population Size
Biggest Threat
Most Distinctive Feature
Regeneration ability
Other Name(s)
The Benjamin Button jellyfish
Gestation Period
2-3 days
Temperate to tropical saltwater worldwide
Larger jellyfish, sea anemones, tuna, sharks, swordfish, sea turtles, penguins
Favorite Food
Plankton, fish eggs, larvae, brine shrimp
Common Name
Immortal jellyfish, Benjamin Button jellyfish
Number Of Species

Immortal Jellyfish Physical Characteristics

Skin Type
Top Speed
4.97 mph

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The immortal jellyfish can regenerate and live forever.

The immortal jellyfish, sometimes called the Benjamin Button jellyfish, is one of the only known animals that possess full regenerative capabilities, as well as being the only species of jellyfish with an indefinite lifespan. It was first documented in 1883 in the Mediterranean Sea. However, researchers and scientists were oblivious to the incredible feats of transformation these jellies perform until the 1980s. It regularly reverts to a sexually immature stage after it has reproduced as well as when it is injured, starving, or dying. The only way it can die is by being eaten, being removed from the water, or contracting diseases.

5 Incredible Immortal Jellyfish Facts!

  • It is unknown how old the oldest immortal jellyfish is.
  • It is the only jellyfish species that does not remain in the last stage, called the Medusa stage, until death.
  • The regeneration process is called “transdifferentiation” and it occurs when the jellyfish’s cells convert to an immature polyp state.
  • The species has also been found on the Atlantic Ocean side of Panama, Spain, and Japan. It has spread throughout the world after getting caught in the ballast waters of long-distance ocean cargo ships.
  • If it starves or gets sick in its immature state when it’s called a polyp, it cannot regenerate and will die.

Classification and Scientific name

Immortal jellyfish, Sarigerme Turkey

Immortal jellyfish, Sarigerme Turkey


The scientific name of the immortal jellyfish is Turritopsis dohrnii. Although it is in the Cnidaria family, it is not a true jellyfish, which is in the class Scyphozoa, not Hydrozoa. The species was formerly classified as Turritopsis nutricula along with other jellyfish species. It was named by German marine biology student August Friedrich Leopold Weismann in 1883. Due to its cell transformation ability which reverts it to an immature state, it is also called the Benjamin Button jellyfish. Closely related species are Turritopsis rubra and Nemopsis bachei.


The ability for medusae to revert back into polyps after reproducing is wholly unique to the immortal jellyfish, this astonishing trait was first discovered accidentally by biologists Christian Sommer and Giorgio Bavestrello in the 1980s. After collecting a specimen of this jelly, they noticed that the medusa converted directly into a polyp when it became stressed, skipping over the entire process of fertilization. When their findings were published it sent shockwaves of disbelief through the scientific community, as this was equivalent to discovering a frog could turn back into a tadpole! After confirming their findings were correct, the Immortal Jellyfish has gone on to become a field of particular interest for geneticists seeking to utilize these creatures’ specially adapted regenerative properties to better understand how to repair and restore other lives. Despite their potential for infinite life, the Immortal Jellyfish has proven to be incredibly difficult for scientists to study in captivity, and only one biologist, Kyoto University’s Shin Kubota has been the only successful cultivator of these fascinating creatures in captivity.


There is only one species of immortal jellyfish. However, over 2,000 species of jellyfish exist.


Immortal Jellyfish


The immortal jellyfish is almost invisible, resembling an ice cube or glass. Its body is bell-shaped and transparent with a minuscule height of 0.18 inches and a diameter of 0.18 to 0.4 inches, making it smaller than a pinky nail. Its body is mostly taken up by its stomach which is vibrant red and has a cruciform shape in its cross-section. Inside their transparent membrane, immortal jellyfish have a hydrostatic skeleton called a mesoglea which has a jellylike substance mostly consisting of water, and it is consistently thin except for the apex. The epidermis (skin) in the cap has a dense cluster of nerve cells that forms a large ring shape above the radical canal, a common feature for cnidarians. Younger immortal jellyfishes are 0.04 inches in size and have 8 tentacles, while adult ones can have up to 80-90 tentacles. The tentacles are white in color.

In its immature polyp state, it is made up of stolons (stems) and upright branches with feeding polyps capable of forming medusa buds. Its polyp form lives attached to the ocean substrate and is also known as a hydroid. Polyps live in the parent hydroid colony for a few days and develop into tiny 0.039-inch medusae which then swim free and live solitarily. The hydroid with several polyps is a unique trait and not a common feature of most jellyfish.

Some immortal jellyfish experience genetic variations influenced by the conditions of their environment. For example, those living in tropical waters have 8 tentacles, while those in more temperate waters have 24 or more tentacles.

Distribution, Population, and Habitat

Immortal Jellyfish Isolated

Immortal Jellyfish Isolated

©Rebecca Schreiner/

Few facts exist about the population size of the immortal jellyfish. The habitat it was initially discovered in was the Mediterranean Sea. However, it actually lives in worldwide coastal areas featuring tropical and temperature waters as it has spread by hitchhiking in the ballast water of long-distance cargo ships. Its preferred habitat is warm water and like other jellyfish, has been found on both the bottom of the ocean as well as near the surface.

Predators and Prey

The typical diet of the immortal jellyfish contains any smaller creatures it can consume in one of two ways: Passively while immature as a hydroid on the ocean floor with any passing prey, or actively hunting and using its stinging tentacles as it drifts through the water. Its diet consists mainly of plankton, fish eggs, larvae, and brine shrimp, while its predators are larger jellyfish, sea anemones, tuna, sharks, swordfish, sea turtles, and penguins.

Reproduction and Lifespan


Immortal jellyfish reproduce both sexually and asexually, but it is not hermaphroditic. The sexually mature medusa stage reproduces by the spawning and fertilization of eggs with sperm, while the sexually immature polyps reproduce by budding. It is the unique life cycle with transformation back into the polyp state that can result in so many genetically identical offspring and no limit on lifespan. Learn about the longest living animals here.

In sexual reproduction, the sperm fertilizes the eggs, after which the egg develops. The jellyfish hatch as larvae, called planula, and swim out on their own. Helping to propel them through the water are small hairs called cilia which are on their tiny, oval-shaped bodies. After a few days, it is time for the next stage of the life cycle and the planula larvae drop down to the ocean floor and attach themselves to a rock. They then undergo transformation into a cylindrical colony of polyps, which become a parent hydroid colony of genetically identical, free-swimming medusae through spawning. The offspring grow into adults in a matter of weeks.

Scientists and researchers have only been able to observe the transformation of the immortal jellyfish in captivity, not in the ocean. At the same time, however, it is difficult to keep in captivity. Only one scientist so far, Shin Kubota from Kyoto University, has managed to keep a group for a long period of time.

The immortal jellyfish’s regeneration ability involves the transformation of its cells to a sexually immature state. Due to its unique life cycle, it does not have a fixed lifespan like other jellyfish species. The gene in mitochondrial DNA (mRNA) discovered to be responsible for its transformation is medusae stage-specific and expresses itself tenfold more than in other stages of the life cycle.

Immortal Jellyfish in Fishing and Cooking

The immortal jellyfish is not considered a pet and due to its small size, it is not used in cooking, although jellyfish are edible and larger species are consumed, particularly in Asian countries.


Immortal Jellyfish

Immortal Jellyfish

©Fon Duangkamon/

The immortal jellyfish have massive populations that are genetically identical, and like other jellyfish species, they go through dramatic population booms. Predation reduces their population to smaller levels.

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About the Author

My name is Corinna! In my profile photo you can see me with one of my two cats, Bisky! The other's name is Yma and she's a beautiful black Bombay kitty. I'm 24 years old and I live in Birmingham, AL with my partner Anastasia and like to spend my free time making music, collecting records and reading. Some other animals I've owned were a hamster, 2 chihuahuas and many different kinds of fish.

Immortal Jellyfish FAQs (Frequently Asked Questions) 

How long do immortal jellyfish live?

They can theoretically live forever, given no harm in the polyp stage and no disease or loss of food and habitat in the medusa stage.

What do immortal jellyfish eat?

Immortal jellyfish eat tiny sea creatures including plankton, fish eggs, larvae, and brine shrimp.

How many immortal jellyfish are there?

It is unknown how many immortal jellyfish there are, but they exist worldwide.

Are immortal jellyfish dangerous?

Immortal jellyfish can sting, but they are not poisonous, unlike the box jellyfish which is also tiny at just 0.98 inches.

What species are similar to the immortal jellyfish?

Turritopsis rubra and Nemopsis bachei.

Are there other immortal cnidarians?

The Hydra is another immortal cnidarian.

What Kingdom do Immortal Jellyfish belong to?

Immortal Jellyfish belong to the Kingdom Animalia.

How do Immortal Jellyfish have babies?

Immortal Jellyfish lay eggs.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.


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