Weird and Wonderful World: Immortal Jellyfish

By Magdalena Zdanowicz

Yes, you definitely read the title right, there is an immortal animal on this Earth… technically. Ok, before you stop reading because you saw the word “technically”, this animal is far more intriguing than any fictional being. Just because it is not like a vampire that everytime it dies it instantly comes back to life, does not mean that it is boring. This species called Turritopsis dohrnii was discovered in the 1880s in the Mediterranean Sea. The start of its life is very much the same as all jellyfish. It starts as a fertilized egg and develops into a larva called a planula. It starts enjoying swimming in the sea but then settles on the seafloor and grows into cylindrical colonies of polyps. These then develop into the marine animals that we recognize as jellyfish in a matter of weeks. Now this is where the Turritopsis dohrnii develops some differences between other jellyfish. Not only is it smaller than a pinky nail when it is fully grown, but they also have an overpowered survival skill.

Now, the question, “is this jellyfish really immortal” has a very complicated answer. This jellyfish, when it gets hurt or is starting to starve, leaps back in its development process to become polyp again, so essentially they are time travelers. This polyp then develops again and is genetically identical to the injured adult. They can do this over and over again throughout their lives. This cellular process, called transdifferentiation, that was observed by scientists in the 1990s, arose a question that all scientists desperately wanted to answer: Can this process be applied to human cells?

In the process of transdifferentiation, an adult cell that is specialized for a particular tissue can become an entirely different type of specialized cell. This is huge because this process doesn’t need the extra middle step that humans have to go through which is making a cell undifferentiated and then making it a stem cell. Stem cells are used to heal organs in the human body but it is only done artificially. Peniel M. Dimberu clarifies and talks more about the difference between these two systems in his article called "Immortal Jellyfish Provides Clues for Regenerative Medicine." He says “Stem cells are cells that can differentiate into any type of cell. They can be isolated from a natural state i.e. embryonic stem cells (ESCs), or created by taking already differentiated cells and coaxing them to differentiate into stem cells, becoming induced pluripotent stem cells (iPSCs). These stem cells can then differentiate into another type of cell. On the other hand, transdifferentiation doesn’t require the middle step of becoming a stem cell. Any differentiated cell can become any other differentiated cell, given of course that it receives the correct signals.” (Dimberu).This means that the Turritopsis can recycle the cells that are damaged and switch them out with fresh, clean, shiny new ones that are differently specialized, on its own. Also, cells can multiply according to the cell theory which states that all cells come from pre-existing cells. That said, the cells that are perfectly healthy can be transferred to a different part of the organism that is sick and can switch it's specialization, and then that part of the organism that lost the specialized cells can multiply the ones they need because cells can multiply, causing the overall outcome to be that the organism just healed itself. Now let's go back to the question, Can this process be applied to human cells? Scientists don’t know that yet, but maybe a better question for now would be: Why should we care? Well, because if we could find a way to skip that middle step of first transforming a cell into a stem cell, then the human body would essentially heal itself. However, scientists are still trying to figure this out because it seems that most people’s dreams are to be immortal so in a sense these jellyfish are living that dream.