Details emerge about MECHANISM of the "INDEFINITE"...

Mainstream media is having a field day - paywalled news reports on Wall St Journal, etc. Cutting thru the hype, I think a worthwhile general-public report is https://www.reuters.com/lifestyle/science/scientists-find-clues-what-makes-immortal-jellyfish-immortal-2022-08-29/

It leaves out plenty - but the original paper is freely available (https://www.pnas.org/doi/10.1073/pnas.2118763119)

BACKGROUND

Turritopsis dohrnii is a type of jellyfish - a tiny one (3mm) - that "can roll back their biological clock when injured or on the verge of starvation. This means, in theory, they could live forever."

For more general info on this fascinating organism, a 2021 article by a professor at Texas A&M: https://www.sciencefocus.com/nature/immortal-jellyfish/

NEW DISCOVERIES

In the 2022 paper in the Proceedings of the National Academy of Sciences, the authors compare this jellyfish with a related one that does NOT have the same rejuvenation mechanisms.

From the paper's abstract (my highlights):

"We present and compare whole-genome assemblies of T. dohrnii and the nonimmortal Turritopsis rubra ..., together with the transcriptome of life cycle reversal (LCR) process of T. dohrnii."
"We compare a set of almost 1,000 genes related to aging and DNA repair between both Turritopsis and other cnidarians and present a stage-specific transcriptome of life cycle reversal process of T. dohrnii."
"We have identified variants and expansions of genes associated with replication, DNA repair, telomere maintenance, redox environment, stem cell population, and intercellular communication."

(Notice the "usual suspects" of the aging process: "DNA repair", "Telomere maintenance", etc...)

Furthermore, the article points to a specific mechanism involved: the silencing of the "polycomb repressive complex 2" (PRC2). For general background info: https://en.wikipedia.org/wiki/PRC2

MY THOUGHTS

Natural evolution operates at the gene level; organisms are generally only "disposable carriers of the genes", sadly. But, in the "search space" of evolution, apparently there are rare scenarios when re-using the organism instead of discarding it, proves convenient, like for this diminutive jellyfish.

The take-home message is that rejuvenation (life cycle reversal) is eminently possible biologically, even in adult organisms - albeit a capability rarely used by evolution.

Of course, all this is far less surprising nowadays, in our age of iPSC (induced Pluripotent Stem Cells) and Yamanaka factors... but, still, I think the psychological impact of such a phenomenon being eminently possible (in relatively higher organisms such as jellyfish) cannot be understated!