Getting old is tough. You start to look back on your life and think about opportunities you might have missed, moments you’d like to relive, and the waning vitality of youthfulness. At some point, you might have even thought, Wow, I wish I could just go back to being a toddler and start this whole journey over again. Unfortunately, that’s impossible, unless you’re one specific kind of jellyfish.
Turritopsis dohrnii, which has become colloquially known as the “immortal jellyfish”, has been discovered to be able to revert back to an infantile state when faced with danger, injury, or the normal stresses of aging. Thus, this incredible species actually possesses the ability to live forever. This discovery, as with many scientific discoveries, was made entirely by accident. However, the cellular process that this organism undergoes to perform this function could have major impacts on the field of stem cell research.
Unless the immortal jellyfish is eaten by another sea creature or falls victim to disease, it is believed that these incredible animals will actually live forever. They’ve found a loophole in the normal biological succession of maturation and death, and can basically hit the reset button on life whenever they find it necessary. Could this discovery be the secret to prolonging life in human beings? Perhaps. Will we create an immortal race of human-jellyfish hybrids in the future? I sure hope not.
Immortal Jellyfish Details
There’s been a great deal of difficulty trying to differentiate between three species within the Turritopsis genus. Turritopsis nutricula can be found in the Caribbean and around North America, and have often been mistaken for Turritopsis dohrnii, as the two species are extremely similar physically. Additionally, Turritopsis rubra, which is found in the waters around New Zealand, has also been commonly mistaken for Turritopsis dohrnii. While these three species are all very similar in appearance, Turritopsis dohrnii is the only one of the three that has been observed to have the ability to reverse its life cycle and live eternally.
When fully grown, Turritopsis dohrnii is about 4.5 millimeters in diameter, smaller than the size of your pinky nail. Their bodies consist of a transparent bell with a red stomach-like center, and they have up to 90 white tentacles stemming from the rim of their bell. They have been observed in many different parts of the world, but they originate in the Caribbean and the Mediterranean.
Turritopsis dohrnii feed primarily on zooplankton, as well as the occasional fish egg or small mollusk. Due to their simple composition, they are preyed upon by a wide range of species, including sea anemones, tuna, sharks, swordfish, sea turtles, penguins, and other jellyfish. If an immortal jellyfish is able to stay out of the clutches of a predator, though, they really can live forever.
The immortal jellyfish is not only good at staying alive, it’s also quite prolific at invading foreign waters. While many marine species have been known to hitchhike around the world in the ballasts of ships, immortal jellyfish have been identified as being particularly well adapted to surviving long journeys on cargo boats.
The Life Cycle Reversal
The immortal jellyfish’s ability to live eternally is thanks to its special ability to revert back to an earlier stage in its life cycle, a process that they can perform as many times as they want. Imagine a butterfly reverting back into a caterpillar over and over again and never dying.
Like every other kind of jellyfish, Turritopsis dohrnii begins its life as a larva, which is called a planula. The planula develops from a fertilized egg and is released by the parent. At first, the planula will swim around until it settles somewhere on the seafloor. The planula will then grow into a cylindrical column of genetically identical polyps, which eventually become the free-swimming individuals that we commonly identify as jellyfish. These free-swimming individuals are called medusae, and they will grow into full-sized adults in just a few weeks.
Normally, in the hydrozoan (the class that contains jellyfish) life cycle, the medusae will grow into sexual maturity, spawn new planula, and eventually die. This, however, is not the case with the immortal jellyfish.
Back in the 1980s, a professor named Ferdinando Boero and two of his students made a shocking discovery by accident. If put under any sort of stress, the immortal jellyfish will fall back to the seafloor and transform back into a polyp, skipping the fertilization and larva stages of the life cycle. In this way, these animals are essentially turning the dial back on their life cycles and reverting to an earlier stage.
The biological process that Turritopsis dohrnii undergoes to make this happen is known as transdifferentiation. Basically, as cells develop in the life cycle, they all take on different functions, a process known as differentiation. In humans, for instance, some of your cells will become kidney cells, some will become brain cells, and some will become skin cells. In transdifferentiation, this process is first reversed, causing these differentiated cells to go back to an undifferentiated stem cell state, and then they again differentiate to serve a different function. It’s almost like if you were to become a plumber, and then you decided to forget everything you know about plumbing, and start becoming a firefighter instead.
This process of transdifferentiation allows the immortal jellyfish to dedifferentiate its cells, and rearrange its body plan completely from that of a fully-formed medusa back into a polyp. This process can be repeated over and over and over again, giving these animals the ability to reverse their aging process an infinite number of times. Hence, this is why some have come to consider these jellyfish immortal.
While this phenomenon has been most extensively researched in Turritopsis dohrnii, studies have shown that other cnidarians may possess the same ability as well. The process of transdifferentiation has become of particular interest to researchers in the medical sciences, as it could have applications in treating areas of tissue that have been damaged by disease.
Medical Implications of Transdifferentiation
People in the medical sciences and in the media have become very excited about the potential impacts that studies around the immortal jellyfish’s genome could have. Every cell has the necessary information to create an entirely new organism; however, once cells become differentiated, this information becomes largely unused.
Scientists are still unsure about the exact molecular process that causes cells in Turritopsis dohrnii individuals to revert back to the state of a stem cell, but the answer could lead to major strides in stem cell research and cancer treatments. The idea is that we might someday be able to trick cancer cells into transdifferentiation and reverting back to young, healthy cells. There’s still a great deal of research to be done, but things look promising.
Others have suggested that understanding the process of transdifferentiation could be the key to anti-aging treatments in humans that might allow us to drastically increase our lifespans. While that may seem far-fetched, people are already using stem cell therapy to achieve cosmetic and medical anti-aging effects.
Perhaps the immortal jellyfish could be the key to more effective cancer treatments, or maybe it could tack on another couple of years to your lifespan, or maybe it will help you keep your skin smooth into your old age. Who knows? Will we ever unlock all of the immortal jellyfish’s secrets and create an immortal race of human beings? It’s possible. However, with the problems of hunger and overpopulation, I think it’s better to focus on cancer treatments at this point in time.