Immortal Jellyfish

Quick Take

• This jellyfish can technically live forever, though one specific condition strips away that superpower entirely. See the life cycle →
• Scientists stumbled onto this creature's secret by accident, and what they witnessed was so bizarre the entire scientific community refused to believe it. Discover the accidental find →
• Only one person in the world has successfully kept these jellyfish alive in captivity, and the reason they're so hard to study is stranger than you'd expect. Why captivity is so hard →
• The process that makes this jellyfish biologically immortal has a name, and geneticists think it could change how we understand human life and death. Explore transdifferentiation →

The immortal jellyfish, sometimes called the Benjamin Button jellyfish, is one of the only known animals that possesses full regenerative capabilities, and is among the few known organisms with a theoretically indefinite lifespan. 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.

4 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.
• If it starves or becomes sick in its immature state, when referred to as a polyp, it cannot regenerate and will die.

Classification and Scientific Name

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 evolutionary biologist August Friedrich Leopold Weismann in 1883. Closely related species are Turritopsis rubra and Nemopsis bachei.

Origin and Species

The ability for medusae to revert 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 that 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 Kyoto University’s Shin Kubota is the most prominent cultivator of these fascinating creatures in captivity, holding what is widely regarded as the only known captive population.

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

Appearance

The immortal jellyfish’s 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 radial canal, a common feature for cnidarians. Younger immortal jellyfish are 0.04 inches in size and have 8 tentacles, while adult ones can have up to 80 to 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

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 temperate 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, it has been found on 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

The sexually mature medusa stage reproduces by 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.

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 transform 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. Analysis of mRNA across each life stage revealed that a medusae stage-specific gene expresses itself tenfold more than in other stages of the life cycle.

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.

Population

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.