My answer to Could there be a lifeform that changes its DNA to survive in any circumstances?
Answer by Connie b. Dellobuono:
How are the jellyfish immortal?
To understand how the Turritopsis dohrnii are able to achieve immortality it important to understand how these jellyfish grow. Similar to other jellyfish, the Turritopsis dohrnii starts out as a larva (a developed fertilized egg). This larva swims around the ocean floor in order to find a safe spot to develop into a jellyfish. Once it finds a place on the ocean floor, it will grow into a colony of polyps, which then clone themselves to become ephyra (the baby jellyfish), which will become the adult jellyfish.
What sets the Turritopsis dohrnii apart from other jellyfish is that whenever it incurs physical damage or it is suffering from starvation, its cells will take a step back in their development and the jellyfish will become a polyp again with identical DNA as before. From here it will grow into a jellyfish again. This process can happen an unlimited amount of times, but it only occurs when the jellyfish suffers from physical damage or possibly starvation. This process is called transdifferentiation.