Immortal Jellyfish [the only animal which can live eternally!]

Would you like to have the ability to transform back to a younger version of yourself? Meet Immortal Jellyfish (scientific name: Turritopsis dohrnii), the only species on Earth which can live (theoretically, at least) an eternal life.

One of the most amazing and incredible organisms living in the oceans is the Turritopsis dohrnii, popularly known as the “immortal jellyfish”.  It is a tiny, transparent jellyfish, originally found in the Mediterranean Sea and in the waters of Japan (but nowadays it travels the world in the ballast tanks of cargo ships). It has a maximum diameter of about 4.5 millimeters or 0.18 inches.

The thing that makes this strange, almost alien-like creature so incredible is that it is biologically immortal. It’s the only known animal capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual.

It can of course die if consumed by another animal (and they certainly are eaten) or if a disease strikes. So, they are not un-killable.

Life Cycle and Reproduction of the Immortal Jellyfish

Most jellyfish species have a relatively fixed life-span, which varies by species from hours to many months. But Turritopsis dohrnii is capable of reverting completely to its polyp state (sexually immature stage) after having reached maturity, by a specific transformation process that requires the presence of certain cell types (tissue from both the jellyfish bell surface and the circulatory canal system). The process is kind of like a butterfly changing back to a caterpillar instead of dying, or an aged chicken turning back into an egg.

1. Fertilization. The life of immortal jellyfish begins when eggs and sperm released by mature jellyfish meet.
2. Planula. In its larval stage (its larva called a planula), it is shaped a bit like a miniaturized and flattened bean.
3. Attached planula. The planula settles on a solid surface on the seafloor and develops a mouth and tiny tentacles.
4. Polyp. It then grows into a cylindrical colony of polyps. An adult Turritopsis dohrnii can return to this stage of development through cell transdifferentiation (see notes 1).
5. Buddying Polyp. The polyp reproduces asexually by dividing in half repeatedly to produce genetically identical copies.
6. Ephyra. Segments detach from the polyp and drift off into the sea.
7. Juvenile. Over a few weeks or months, the young jellyfish matures into an adult.
8. Adult. As it reaches sexual maturity, the T. dohrnii has the option of reverting back to the polyp stage (#4), instead of dying! When they become threatened by a physical injury or even starvation, they can transform back into a polyp stage within three days. They retract their tentacles, shrink their bodies, and go back to the ocean floor to start the cycle all over again. It can make this transformation many times once it reaches adulthood.

This process is not fully understood, because the jellyfish has only been observed under a microscope a few times. Many polyps do not make it to adulthood due to predators, illness or starvation.

Furthermore, the “immortality” steps in only when T. dohrnii suffers an attack by a predator, or starvation, or some kind of environmental stress.

These are the reasons why this “immortality” process hasn’t been observed in nature yet.

Related: “The Deep Sea”: life in the depth of the oceans

The “regeneration” cycle of T. dohrnii has inspired many researchers to hopefully find a way of using stem cells to renew damaged, aged, or even dead tissue in humans. So, one day in the future humans may live for hundreds or even thousands of years.

T. dohrnii, T. nutricula and T. rubra

The “immortal jellyfish” was formerly classified as T. nutricula. Since the genus Turritopsis can be found in almost every part of the world’s oceans, there was a lot of confusion even inside the scientific community between the three types of the genus: the dohrnii, the nutricula, and the rubra. It is not an easy task to differentiate between these tiny jellyfishes.

The nutricula was for a long time mistakenly the one referred to as the immortal jellyfish, while the jellyfish used in the lab observations was the T. dohrnii, as they were collected from the Mediterranean, where it originally found. The nutricula is found in the Caribbean and North America and the cycle reversal was not in fact observed on the nutricula (see notes 2).

Until a recent genetic study, it was thought that Turritopsis rubra and Turritopsis nutricula were the same. It is not known whether or not T. rubra medusae can also transform back into polyps.

Notes

1. Transdifferentiation, also known as lineage reprogramming is the conversion of a cell type present in one tissue or organ into a cell type from another tissue or organ without going through a pluripotent cell state.
2. Some sources, including Wikipedia, claim that once reaching adulthood, T. nutriluca can transfer its cells back to childhood, too.

Sources

• Life cycle and reproduction of  Turritopsis dohrnii
• Turritopsis dohrnii on Wikipedia
• “The strange life of the immortal jellyfish” on abc.net.au
• “Immortal Jellyfish – The creature that defies death” (a dedicated webpage)
• Immortal jellyfish: Does it really live forever? on mnn.com

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M. Özgür Nevres

I am a software developer and a science enthusiast. I was graduated from the Istanbul Technical University (ITU), Computer Engineering. In the past, I worked at the Istanbul Technical University Science Center as a science instructor. I write about the planet Earth and science on this website, ourplnt.com. I am also an animal lover! I take care of stray cats & dogs. This website's all income goes directly to our furry friends. Please consider supporting me on Patreon, so I can help more animals!

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