Thread: Are there truly immortal organisms on Earth?

I have heard, informally, that jellyfish, water bears (tardigrades) and lobsters are capable of longevity if not downright immortality. Are these statements realistic? Are there any truly immortal organisms?

List of longest-living organisms - Wikipedia, the free encyclopedia

It looks like the "immortal jellyfish" could be a contender. Some of the others on those lists are pretty interesting, but not immortal.

Originally Posted by jimmythesaint

I have heard, informally, that jellyfish, water bears (tardigrades) and lobsters are capable of longevity if not downright immortality. Are these statements realistic? Are there any truly immortal organisms?

You are probably referring to this post (cf. post #116), and I will add the same remark as I did there.
Biological immortality (which seems to be a rather contradictory concept) does not imply that it is invulnerable,
as it is susceptible to diseases and predators (due to its position in the food chain), nor is biological immortality observed in nature.

If it is shown that T. dohrnii (or any other species) can cycle indefinitely between its two phases in nature, then I may accept it as biological immortal.
To answer your question: I do not think that there are truly immortal organisms (given the evidence we have now).

I have heard of hydra being immortal or resisting senescence (deteriorative ageing) but I do not know the credibility of the following account:

To test for the presence or absence of aging in hydra, mortality andreproductive rates for three hydra cohorts have been analyzed for a period of four years. The
results provide no evidence for aging in hydra: mortality rates have remained extremely low
and there are no apparent signs of decline in reproductive rates. Hydra may have indeed
escaped senescence and may be potentially immortal

http://www.biochem.uci.edu/Steele/PD...ence_paper.pdf

I find this possibility mind-blowing and inspiring.

Originally Posted by jimmythesaint

I have heard of hydra being immortal or resisting senescence (deteriorative ageing) but I do not know the credibility of the following account:

To test for the presence or absence of aging in hydra, mortality andreproductive rates for three hydra cohorts have been analyzed for a period of four years. The
results provide no evidence for aging in hydra: mortality rates have remained extremely low
and there are no apparent signs of decline in reproductive rates. Hydra may have indeed
escaped senescence and may be potentially immortal

http://www.biochem.uci.edu/Steele/PD...ence_paper.pdf

I find this possibility mind-blowing and inspiring.

I do not see any errors in the study, nor do I see problems with the journal it is published in.

It is possible that the length of the observational study was too short to observe senescence in the subjects (the author admits this),
but Hydra has shown that it could be another example of biological immortality. Of course, this conclusion would be better supported if longer observational studies are set up.

Originally Posted by jimmythesaint

I have heard, informally, that jellyfish, water bears (tardigrades) and lobsters are capable of longevity if not downright immortality. Are these statements realistic? Are there any truly immortal organisms?

At the point that we are discussing the immortality of a Jellyfish, we have to veer into philosophy. Specifically, Theseus Ship. If none of the cells of the Jellyfish are the same, is it truly the same organism? Eventually, all of the cells will be different. If we can assert that after one or even a million generations of total cellular change, it is still the same lifeform, what is to stop us from asserting than when a single cell splits, each of the new cells are the same cell as opposed to offspring? Maybe we can, maybe it is different because there are now two organisms. Either way, it seems like an arbitrary distinction with more of a basis in labeling conventions then how life actually works. But I am willing to suspend that and assume that the Jellyfish is the same organism after a thousand years so we can actually examine the question you are asking.

Of course, even if we define the Jellyfish as the same Jellyfish despite a complete cellular overhaul it won't actually live forever, even in a vacuum system where no external force kills it. Entropy/homeostasis eventually wins out and energy will become evenly distributed within that self-contained system. This is also true of the real world, but of course some external factor will have killed it long before then. So, no, it cannot be truly immortal. But can it be functionally immortal? That's above me, scientifically as well as philosophically. I would guess 'yes, if your definitions are broad enough.'