9. Some jellyfish are immortal – The tiny Turritopsis dohrnii jellyfish has a remarkable life cycle: after reaching sexual maturity it can revert back to a juvenile state. There is no apparent limit to how many times it can do this, meaning it could theoretically live forever. While most T dohrnii die in the conventional manner, in times of crisis they can transform into a polyp state, a process called transdifferentiation. This lets them reproduce asexually to start a new colony. Unique in the animal world, this has helped them spread to oceans across the world.
