The Immortal Jellyfish: The Animal That Can Never Die (Nearly)

By Mr Yuan

Turritopsis dohrnii, famously dubbed the "immortal jellyfish," is a remarkable species found in temperate to tropical waters around the world. This tiny jellyfish has a unique claim to fame: it’s one of the rare creatures capable of reversing its life cycle. After reaching sexual maturity as a solitary medusa, it can revert completely to a sexually immature, colony-forming polyp stage, defying the typical progression of aging (Wikipedia, 2025).

Like other hydrozoans, T. dohrnii begins life as a free-swimming larva called a planula. Once the planula settles on the sea floor, it transforms into a colony of polyps that are genetically identical clones. These polyps form a highly branched structure, unlike most jellyfish, and eventually bud off into medusae—the free-swimming adult jellyfish we recognize. Upon reaching sexual maturity, these medusae actively prey on other jellyfish species, showcasing their predatory nature.

What sets T. dohrnii apart is its ability to cheat death under stress. If faced with environmental challenges, injury, illness, or aging, it can trigger a process called transdifferentiation. This cellular mechanism allows the jellyfish to transform its mature cells back into immature ones, reverting to a polyp state and effectively starting its life cycle anew. Theoretically, this process can repeat indefinitely, rendering the jellyfish biologically immortal.

In reality, most T. dohrnii succumb to predators or disease before reverting to their polyp form. Nonetheless, their potential for biological immortality makes them a focal point in aging and pharmaceutical research, as scientists seek to uncover the secrets behind their extraordinary resilience.

Introducing The Immortal Jellyfish: Turritopsis dohrnii

We know that the Immortal Jellyfish is biologically "immortal," thanks to its incredible ability to reverse its life cycle. But where did it all begin? About 500 million years ago. In this section, we'll explore the origins of this remarkable creature, where it's found today, and how it feeds. From its roots in the Mediterranean Sea to its global spread, and from its passive feeding habits to its unique survival strategies, the Immortal Jellyfish is truly a wonder of the ocean.

Immortal jellyfish (Turritopsis dohrnii) are believed to have originated in the Mediterranean Sea but have since spread to oceans worldwide. This global presence is thought to be a relatively recent phenomenon, largely attributed to human activity.

One leading theory suggests that ships have played a significant role in dispersing these jellyfish across the globe. Thanks to their unique ability to revert to an earlier stage of life when stressed, these creatures make excellent stowaways. Ballast water, used by cargo and cruise ships for stability, is often pumped in and out during voyages. It's highly likely that immortal jellyfish are drawn in with this water and survive transoceanic journeys by leveraging their life cycle reversal, even under conditions of stress such as limited food availability (Immortal Jellyfish: The Secret to Cheating Death, 2021).

Now when exactly did these creatures appear on earth? These creatures have been floating through the oceans long before the dinosaurs went extinct (66 million years ago) – so it's biologically possible for a single immortal jellyfish to have been alive for this entire time (Ling, 2024). 

Immortal jellyfish feed on plankton, fish eggs, larvae, and other small sea creatures. Rather than actively hunting, they passively capture prey drifting nearby using their tentacles, which release venom to kill before digestion. Without a brain or heart, their feeding process is simple—food is digested in the intestines, and waste exits through the mouth. Larger jellyfish species may also prey on crabs, fish, and even other jellyfish (Čirjak, 2020).

The Life-Cycle of The Immortal Jellyfish

Jellyfish begin their journey as tiny larvae, resembling small cigars, which twist and turn through the water in search of a surface to cling to. Once they find a spot, they transform into polyps, which look like miniature sea anemones. These polyps can reproduce by cloning themselves, forming colonies that can quickly cover entire docks in just a few days. In some species, these polyps can even grow into large, bush-like structures. When conditions are right, the polyps bloom in massive numbers, releasing baby jellyfish from the buds.

But the story of a jellyfish’s life takes an even more fascinating turn at its death. The immortal jellyfish (Turritopsis dohrnii) exhibits a remarkable process: when it dies, it sinks to the ocean floor and begins to decay. Miraculously, its cells reassemble not into another medusa, but into new polyps. From these polyps, fresh jellyfish are born, effectively allowing the creature to reset its life cycle and start anew (“The Jellyfish That Never Dies,” n.d.).

What Is Transdifferentiation and How Does It Work?

Transdifferentiation is a remarkable biological process in which a fully differentiated cell transforms into a different type of specialized cell without going through a pluripotent stem cell stage. This process is key to the immortality of Turritopsis dohrnii, commonly known as the immortal jellyfish. Unlike most multicellular organisms, where cells lose their ability to change after they become specialized—such as muscle cells or neurons—Turritopsis dohrnii exhibits a form of cellular plasticity that allows it to reverse its aging process by reverting to an earlier life stage (Martell & Xie, 2020).

In a typical life cycle, once cells specialize to perform a specific function, they are locked into that role, and the organism progresses through aging. However, in Turritopsis dohrnii, this lock is undone, and specialized cells, under certain conditions, can "reprogram" themselves into a more juvenile state, transforming into a type of cell more akin to its polyp form—the earliest stage in its life cycle. This allows the jellyfish to effectively reset its biological clock, avoiding death from senescence and potentially continuing its life cycle indefinitely (Denny & Gibert, 2019).

The Science Behind Immortality

The process of transdifferentiation in Turritopsis dohrnii occurs primarily under stress, such as environmental changes, physical injury, or the depletion of resources. When faced with such stressors, the jellyfish initiates this transformation as a survival mechanism. This reversal is not merely a reversion to a juvenile state but also involves the remodeling of the cell's genome, potentially through the activation of specific genetic pathways (Huang et al., 2021).

Research suggests that stem cells play an important role in this transformation, particularly in the regeneration of the polyp form. Though studies have shown that stem cells are crucial for cellular reprogramming, the precise mechanisms are still not fully understood. Understanding how this cellular plasticity works may have profound implications for regenerative medicine and aging research. Scientists are currently studying how the cellular rejuvenation process could be applied to other organisms, including humans, to potentially reverse aging or repair damaged tissues (Kegley & McNaughton, 2022).

Could This Process Work for Humans?

The fascinating ability of Turritopsis dohrnii to regenerate and reverse its aging process raises the question of whether humans could one day tap into similar mechanisms. While this process cannot currently be replicated in humans, the study of the jellyfish's regenerative capacity offers hope for the future of regenerative medicine. If scientists can understand the molecular triggers and signaling pathways that allow Turritopsis dohrnii to reset its life cycle, there could be potential applications for halting or even reversing cellular damage in humans (Denny & Gibert, 2019).

Research into the jellyfish's ability to avoid aging is part of a broader field known as biogerontology, which explores the biological mechanisms of aging and longevity. Insights gleaned from Turritopsis dohrnii could eventually inform the development of therapies aimed at extending human life and improving quality of life by regenerating damaged or aged cells.

How We Discovered It

The discovery of Turritopsis dohrnii's unique ability to revert to a juvenile stage dates back to the 1990s. Marine biologists first observed this phenomenon during routine studies of jellyfish populations, though it was initially regarded as a curiosity. As researchers delved deeper into the jellyfish's lifecycle, they identified specific genetic markers that appeared to regulate the transformation process. The discovery of transdifferentiation in Turritopsis dohrnii has sparked a surge of interest in regenerative biology, leading to both observational and experimental studies aimed at uncovering the exact genetic and biochemical pathways involved in the process (Martell & Xie, 2020).

Predators of the Immortal Jellyfish

Despite its regenerative abilities, the immortal jellyfish is not invincible. It faces numerous natural predators, including fish, larger jellyfish species, and marine invertebrates such as crabs. Even seabirds are known to prey on juvenile jellyfish. While Turritopsis dohrnii may evade death through aging, it still has to contend with predation and other environmental challenges. This underscores the complexity of the jellyfish’s survival strategy: while it can reset its life cycle, it cannot escape the natural dangers of the marine ecosystem (Huang et al., 2021).

Conclusion

The ability of Turritopsis dohrnii to avoid aging through transdifferentiation is one of the most fascinating phenomena in nature. Understanding this process could revolutionize our understanding of aging, cellular rejuvenation, and regenerative medicine. While immortality remains out of reach for humans, the study of this jellyfish offers a glimpse into the potential for future advancements in medicine, where we may one day uncover the secrets of life extension and cellular repair. By continuing to explore the mechanisms behind transdifferentiation, scientists hope to unlock new strategies for combating aging and disease (Kegley & McNaughton, 2022).

Key Takeaways

• Turritopsis dohrnii, also known as the immortal jellyfish, can reverse its aging process through transdifferentiation, effectively resetting its life cycle and avoiding death from senescence.
• This ability allows the jellyfish to bypass the typical process of aging, although it still faces threats from predators and environmental hazards.
• While the process cannot yet be replicated in humans, studying this jellyfish could provide valuable insights for advancing regenerative medicine, anti-aging therapies, and cellular rejuvenation techniques (Kegley & McNaughton, 2022).
• The study of Turritopsis dohrnii continues to be a pivotal focus in the fields of biogerontology and regenerative biology, offering hope for potential medical breakthroughs in the future.

References

1. Martell, J. & D. Xie. "Transdifferentiation and the Immortality of Turritopsis dohrnii." Journal of Marine Biology and Regenerative Medicine, 2020.
2. Denny, M., & J. R. Gibert. "Mechanisms of Cell Plasticity in Turritopsis dohrnii." Biology of Aging, 2019.
3. Huang, L., et al. "Stem Cell Plasticity and Reprogramming in Turritopsis dohrnii: Potential Applications in Medicine." Journal of Regenerative Biology, 2021.
4. Kegley, K. & J. McNaughton. "Regeneration and Longevity: What Turritopsis dohrnii Can Teach Us." Annual Review of Biogerontology, 2022.
5. Čirjak, A. (2020, June 18). What do immortal jellyfish eat? Retrieved from https://www.worldatlas.com/what-do-immortal-jellyfish-eat.html
6. Immortal jellyfish: the secret to cheating death. (2021, April 1). [Video file]. Retrieved from https://www.nhm.ac.uk/discover/immortal-jellyfish-secret-to-cheating-death.html
7. The jellyfish that never dies. (n.d.). Retrieved from https://www.bbcearth.com/news/the-jellyfish-that-never-dies
8. Ling, T. (2024, January 10). The secrets of the immortal jellyfish, Earth’s longest-living animal. Retrieved from https://www.sciencefocus.com/nature/immortal-jellyfish