Turritopsis jellyfish
Turritopsis dohrnii
Turritopsis dohrnii is a jellyfish smaller than a fingernail. When it is starved, injured or stressed, the adult sinks, shrinks into a blob of cells and settles on the bottom. Within one to three days, that blob grows into a polyp, the stage that normally comes before the adult.
The polyp then buds off new jellyfish that are genetically identical to the old one. Each of those can, in principle, run the cycle again, which earned it the name immortal jellyfish. In the wild, most are still eaten, starved or smothered long before they get the chance.
It is like a butterfly turning back into a caterpillar whenever life gets tough.
