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The Creature that Lives Forever

immortal jellyfish swimming through ocean with coral and fish like goldfish or koi in background
The immortal jellyfish has the ability of reverse aging to practically live forever.

Immortality has been a goal of humanity for as long as one can remember. The elixir of life has been a common objective in countless legends and stories over the years. Though immortality may not have been achieved by humans yet, one ocean-dwelling creature seems to have cracked the code for living forever. The immortal jellyfish (Turritopsis dohrnii) has a unique mechanism that has attracted the attention of scientists for its potential contributions to medicine.

The immortal jellyfish has five main stages in its life cycle. In its first stage, it exists as a fertilized egg which floats around in the water before becoming a planula in its second stage. Planulae look like small worms and are able to swim on their own. Planulae then settle down on a seabed and become polyps in the third stage of a jellyfish’s life cycle. Polyps develop new organs, like a digestive system. Polyps can also clone themselves when the conditions are right, and will do so until they create a colony of themselves. The polyps then develop muscles and nerves until they are ready to release from the seabed. At this point, the polyp (and its clones) can become ephyra in their second-to-last stage. Ephyra are like young adults– they can swim, acquire food, and grow all on their own. The final stage of this jellyfish’s life cycle is the medusa. Medusae are adult jellyfish that can reproduce with others of their kind. Most species of jellyfish would die soon after mating, but the immortal jellyfish has a special trick up its sleeve that allows it to avoid this demise.

graphic of immortal jellyfish life cycle from egg to planula or larva to polyp to ephyra to medusa and back to egg
Unlike most organisms, the immortal jellyfish's life cycle is truly cyclic and can go on forever.

The immortal jellyfish, when damaged, has the ability to heal itself and revert to an earlier stage in its life. As a medusa, the immortal jellyfish can become a polyp and grow normally again. This ability to transform from a medusa to a polyp is known as transdifferentiation on the cellular level. In this way, the immortal jellyfish can age in reverse and then grow old again. Thus, in theory, the immortal jellyfish can live forever. However, they can still die from disease, predators, and environmental dangers. Nevertheless, the immortal jellyfish’s reverse-aging technique greatly interests scientists due to its future potential in stem cell research. Stem cells are cells that can repurpose themselves in different areas of the body. They are often used to treat damaged areas. Stem cells in humans are usually taken from early stages in growth because those cells can develop into nearly any cell in the human body. In jellyfish, however, stem cells aren’t even necessary because any adult cell can repurpose itself. In transdifferentiation, an adult cell specialized to perform a certain task in a certain tissue can become a completely different type of specialized adult cell. This technique is very important for scientists because if they can recreate a similar technique in humans, damaged tissue can be replaced much easier than before. Science has already learned a lot from nature in many fields, from engineering to biology, but there is still a lot to learn from the expansive Earth and all of its inhabitants. With these newfound discoveries, we can greatly impact humanity for the better.

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