A-z - Animals

Immortal jellyfish

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The immortal jellyfish can be reborn and become immortal.

Immortal jellyfish No.1

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The immortal jellyfish, sometimes called Benjamin Button's jellyfish, is one of the only animals known to have the ability to fully regenerate, and the only jellyfish species with an infinite lifespan. It was first recorded in the Mediterranean in 1883. However, until the 1980s, researchers and scientists failed to notice the incredible feats of transformation performed by these jellyfish. It usually reverts to sexual immaturity after breeding and when injured, starved or killed. The only way it can die is if it is eaten, removed from the water, or infected with a disease.

5 Incredible Immortal Jellyfish Facts!

  • It's not known how big the oldest immortal jellyfish was.
  • It is the only jellyfish species that does not remain in the final stage (called the Medusa stage) until it dies.
  • The regeneration process, called "transdifferentiation," occurs when the jellyfish's cells transition into an immature polyp state.
  • The species is also found on the Atlantic side of Panama, Spain and Japan. It has spread around the world after being caught in the ballast waters of long-distance ocean-going cargo ships.
  • If it starves or becomes sick in its immature state called a polyp, it cannot regenerate and will die.

taxonomic name

Immortal jellyfish, Sarigerme turkey
Immortal jellyfish, Sarigerme turkey

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The scientific name of the immortal jellyfish is Turritopsis dohrnii . Although it belongs to the family Cnidaria, it is not a true jellyfish, and belongs to the class Aequella, not Hydrozoa. This species was previously classified as Turritopsis nutricula along with other jellyfish species. It was named in 1883 by German marine biology student August Friedrich Leopold Weissmann. It is also known as the Benjamin Button jellyfish due to its cell-transforming ability to return it to an immature state. Closely related species are Turritopsis rubra and Nemopsis bachei .


The ability of jellyfish to transform back into polyps after reproduction is entirely unique to immortal jellyfish, an astonishing property that was first discovered by accident in the 1980s by biologists Christian Sommer and Giorgio Bavestrello. After collecting specimens of the jelly, they noticed that the jellyfish turned directly into polyps when they were stressed, skipping the entire fertilization process. When their findings were published, it sent incredible shockwaves through the scientific community, as it was the equivalent of discovering that frogs can turn back into tadpoles! After confirming their findings to be correct, immortal jellyfish have become an area of particular interest to geneticists trying to exploit these creatures' specially adapted regenerative properties to better understand how to repair and restore other life. Despite their potential for infinite life, scientists have proven difficult to study immortal jellyfish in captivity, and only one biologist, Shin Kubota of Kyoto University, is the only one who has successfully bred these fascinating creatures.

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There is only one type of jellyfish that lives forever. However, there are over 2,000 species of jellyfish.


Immortal jellyfish

© Karajohn/Shutterstock.com

The immortal jellyfish are almost invisible and resemble ice cubes or glass. Its body is bell-shaped, transparent, extremely small at 0.18 inches in height, and 0.18 to 0.4 inches in diameter, smaller than a pinky nail. Most of its body is occupied by its stomach, which is bright red and cross-shaped in cross section. Inside their transparent membranes, immortal jellyfish have a hydrostatic skeleton called the mesoplasma, a gelatinous substance composed mostly of water that is thin all but the tip. The epidermis (skin) in the cap has dense clusters of nerve cells that form a large ring above the root canal, a common feature of cnidaria. Younger immortal jellyfish are 0.04 inches in size and have 8 tentacles, while adults can have up to 80-90 tentacles. Tentacles are white.

In its immature polyp state, it consists of stolons (stems) and erect branches with feeding polyps capable of forming jellyfish buds. Its polyp form is attached to the marine substrate and is also known as a polyp. Polyps live for a few days in a parent polyp colony, then develop into tiny 0.039-inch jellyfish, which then swim freely and live alone. Polyps with multiple polyps are a unique feature and not common to most jellyfish.

Some immortal jellyfish undergo genetic variation influenced by their environmental conditions. For example, those living in tropical waters have 8 tentacles, while those living in more temperate waters have 24 or more.

Distribution, Population and Habitat

Immortal jellyfish isolated
Immortal jellyfish isolated

©Rebecca Schreiner/Shutterstock.com

Few facts are available on the population size of immortal jellyfish. Its original habitat is the Mediterranean Sea. However, it actually lives in coastal regions worldwide characterized by tropical and warm water, as it is spread by hitchhiking in the ballast water of long-distance cargo ships. Its preferred habitat is warm waters, and like other jellyfish, it is found both on the seafloor and near the surface.

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predator and prey

The typical diet of an immortal jellyfish consists of any smaller organism it can consume in one of two ways: passively eating any passing prey while on the ocean floor as a polyp, or actively hunting and using its spiny tentacles while adrift in the water . Its diet mainly consists of plankton, fish eggs, larvae and brine shrimp, while its natural enemies are larger jellyfish, sea anemones, tuna, sharks, swordfish, turtles and penguins.

Reproduction and Lifespan

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The immortal jellyfish can reproduce both sexually and asexually, but it is not hermaphroditic. The sexually mature jellyfish stage reproduces by spawning and fertilization of eggs with sperm, while the sexually immature polyp reproduces by budding. It is this unique life cycle transition back to the polyp state that can produce so many genetically identical offspring with no limit to how long they can live. Learn about the longest-lived animals here.

In sexual reproduction, a sperm fertilizes an egg, which then develops. The jellyfish hatch into larvae, called planula, and swim out on their own. Helping propel them through the water are tiny hairs called cilia that line their tiny oval bodies. A few days later, entering the next stage of the life cycle, the buoyant larva sinks to the seafloor and attaches to rocks. They then transform into a cylindrical colony of polyps that spawn as polyp parent colonies of genetically identical, free-swimming jellyfish. The offspring grow into adults within a few weeks.

Scientists and researchers can only observe the transformation of immortal jellyfish in captivity, not in the ocean. At the same time, however, captivity can be difficult. So far, only one scientist, Shin Kubota of Kyoto University, has been able to maintain a team for a long time.

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The regenerative abilities of immortal jellyfish involve converting their cells to a sexually immature state. Due to its unique life cycle, it does not have a fixed lifespan like other jellyfish species. The genes found in mitochondrial DNA (mRNA) responsible for its transformation were specific to the jellyfish stage, being expressed ten times more than in other stages of the life cycle.

Immortal jellyfish in fishing and cooking

Immortal jellyfish are not considered pets and are not used in cooking due to their small size, although jellyfish are edible and eat larger species, especially in Asian countries.


Immortal jellyfish
Immortal jellyfish

©Fon Duangkamon/Shutterstock.com

Immortal jellyfish have large genetically identical populations, and like other jellyfish species, they experience dramatic population explosions. Predation reduces their numbers to even smaller levels.

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They could theoretically live forever since there is no harm in the polyp stage and no disease or loss of food and habitat in the jellyfish stage.

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

The number of immortal jellyfish is unknown, but they exist worldwide.

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

Turritopsis rubra and Nemopsis bachei .

Hydra is another immortal cnidarian.

Immortal jellyfish belong to the animal kingdom.

Immortal jellyfish lay eggs.