What do you think of this fact?
Imagine getting old or sick, and instead of dying, you just turn back into a kid. For us, that’s science fiction. For one tiny jellyfish, it’s just Tuesday. Its name is Turritopsis dohrnii, and its nickname is the “immortal jellyfish.”
Small, see-through, easy to miss
The medusa, the floating bell-shaped form, measures only about 4.5 millimeters across. That’s smaller than your fingernail. A bright red stomach shows through its transparent bell, and up to 90 white tentacles hang from the edge. The species was described in 1883 and named after Anton Dohrn, founder of the zoological station in Naples, Italy. It originally comes from the Mediterranean Sea.
Back to square one
Normally, a jellyfish’s life only runs one way: a polyp stuck to the sea floor buds off medusae, which grow up, reproduce and die. Turritopsis dohrnii can flip that one-way street. When it’s injured, starving, sick or old, it transforms back into a polyp.
The trick is called transdifferentiation. Cells that already have a specialized job turn into completely different cell types. The new polyp later buds off fresh medusae that are genetically identical to the original. In theory, this can repeat forever.
Japanese researcher Shin Kubota kept a colony in the lab that “rebirthed” itself 11 times in 2 years.
Immortal? Not quite
Before you get jealous: this jellyfish is far from invincible. In the wild, most of them are probably eaten or killed by disease before they ever get to hit reset. Their predators include other jellyfish, sea anemones, tuna, sharks and sea turtles. Biologically immortal just means old age alone doesn’t have to kill it.
Genetically identical individuals have been found in oceans all over the world. They probably hitch rides in the ballast water of cargo ships.
An animal that answers every crisis by starting over from scratch. Honestly, kind of enviable.