What are some of the oldest living organisms?

[dlevitis]

Turritopsis dohrnii can under particular conditions be induced to revert to an earlier life stage, which can then grow into a medusa (the adult) which can then be induced to revert again. This is an amazing trick. It is not clear to me that this process can continue indefinitely, or that the individual expunges all forms of accumulated damage when it undergoes this backward development. So again, I’d say we don’t have enough evidence to be confident that even under very particular conditions the immortal jellyfish escapes from senescence entirely.