No brain, no stomach, no central nervous system, no respiratory system, no circulatory system...You would think jellyfish would be weird enough creatures. But nope. One species has taken "freak" to a whole new level with the ability to be, well, immortal.
Meet Turritopsis nutricula, better known as the immortal jellyfish -- and sometimes known as the Benjamin Button jellyfish because of how it transforms itself from mature adult back into baby form in times of stress or injury. Yep, this species of jellyfish has the ability to revert completely back to its polyp stage after reaching maturity. Essentially, the medusa, or mature form of the jellyfish, can transform into the polyps of a new polyp colony in a process is called cell transdifferentiation. If a mature Turritopsis is threatened — injured or starving, for example — it attaches itself to a surface in warm ocean waters and converts into a blob. From that state, its cells undergo transdifferentiation, in which the cells essentially transform into different types of cells. Muscle cells can become sperm or eggs, or nerve cells can change into muscle cells, “revealing a transformation potential unparalleled in the animal kingdom,” according to the original study of the species published in 1996.
In a New York Times article on the discovery of the ability of this species:
One of the paper’s authors, Ferdinando Boero, likened the Turritopsis to a butterfly that, instead of dying, turns back into a caterpillar. Another metaphor is a chicken that transforms into an egg, which gives birth to another chicken. The anthropomorphic analogy is that of an old man who grows younger and younger until he is again a fetus. For this reason Turritopsis dohrnii is often referred to as the Benjamin Button jellyfish.
Essentially a mature individual can transform itself into polyps, or a whole bunch of baby jellyfish. This cycling through of the stages of life is why it is called "immortal."...