Turritopsis Dorhnii

Although the Turritopsis Dorhnii is only 4,5 mm in diameter, it is a very special kind of jellyfish. Normally, the development of a jellyfish ranges from an egg, to a larva (planula), to a polyp, and finally to their final well-known ‘medusa’ form (see image). The T. Dorhnii also does this, but can go back to the polyp stage (their childhood) once they’ve reached sexual maturity.
It’s self-explanatory that the T. Dorhnii does not go back to the polyp phase just for fun. Experiments have shown that T. Dohrnii placed in difficult environments (such as very cold water or a lack of food) transform to a polyp and stay that way until their environment is back to normal. In normal environments, the jellyfish didn’t return to being a polyp. In other words, this process is used to save resources and survive in all kinds of circumstances. Therefore, this kind of jellyfish is biologically immortal.


To go back to it’s polyp phase (mid-bottom in the image above), the T. Dorhnii uses a process called transdifferentiation. This normally means that an organism transforms one cell to a completely different cell with another structure and function. However, the T. Dorhnii doesn’t do this with the cells in one body part (like a salamander that regenerates its tail), but completely transforms his entire body at once. It’s also not an one-time-only trick, the T. Dorhnii can transform back to a polyp multiple times in its life. However, this does not mean that they are invincible, as they still can get sick or eaten by predators.

For the entirety of human existance, we have been searching for the “elixir of life” to stop aging. Although it might cause some problems like overpopulation and famine when we would add this potential BioBrick to human DNA, it can serve many purposes in other organisms.


  • T. Dohrnii are currently taking over the worlds oceans. Their natural habitat is around the Mediterranean Sea and Japan, but they can also survive well in ships. Big container ships use sea water to be in the right position in the water while their ship is unloaded. When the small T. Dohrnii gets sucked inside this ballast water container, it transforms to it’s polyp phase and just waits until the ballast water is dropped again, which could be anywhere around the world. Who would say no to a free trip around the world like this?
  • The T. Dohrnii stars in multiple TV series, such as The Blacklist (S2E17) and Zoo (S2E6). They’re also found in an animated children’s series called Wild Kratts (episode “Meeting the Immortal Jellyfish”)
  • Although the T. Dorhnii is only 4,5 mm in diameter, it can have up to 90 tentacles when in medusa phase!

Image courtesy medusa: Takashi Murai
Image courtesy jellyfish lifecycle: Getty Images
Image courtesy group: The Asahi Shimbun