‘The Immortal Jellyfish’ sounds like a great name for a band, but it is the nickname given by scientists to a species of the unusual soft and tentacled marine animals because it really is biologically immortal due to its ability to revert back to a larval state after sex and grow itself to adulthood again … and again and again and again ad infinitum. If only we could figure out how they do it … perhaps humans could achieve immortality too. Well, Part A of that equation is now a reality – researchers in Spain have sequenced the genome of the immortal jellyfish and isolated the reason for its never-ending life. Will Part B require becoming part jellyfish?
“Turritopsis dohrnii is the only metazoan able to rejuvenate repeatedly after its medusae reproduce, hinting at biological immortality and challenging our understanding of aging.”
In the new study, “Comparative genomics of mortal and immortal cnidarians unveils novel keys behind rejuvenation” published in the journal Proceedings of the National Academy of Sciences (PNAS), researchers at Universidad de Oviedo in Spain introduce us to Turritopsis dohrnii, the only animal known to have the ability to create a clone of itself repeatedly. T. dohrnii is not an unknown species – they are found worldwide in temperate to tropic waters. Like other jellyfish, they begin life the normal way as larva formed after the union of T. dohrnii sperm and eggs. As they float around in the warm tropical waters, they eventually sink down to the bed, attach themselves and change into polyps. At this point, they form a colony by cloning themselves, eventually reaching the medusa or sexual phase, where they create sperm and eggs and begin the normal process again.
That doesn’t sound like immortality.
You’re right … it doesn’t. Life is tough when you’re a squishy jellyfish and many colonies become stressed by predators, pollution and climate change. That’s when, at some point in its evolutionary history, the T. dohrnii figured out the secret to immortality. According to the study press release, when a medusa recognizes it is in a state where it cannot reproduce normally -- or it reaches a state where aging kicks in and it knows death is near, it resorts to Plan B. Instead of releasing sperm or eggs, the medusa form mysteriously transforms itself into a cyst which is identical to its own polyp stage. back into its polyp stage. That new polyp drops to the ocean floor, attaches to the bed, and begins to form another colony identical to itself. Since the original medusa never really died, it is considered by these scientists to be biologically immortal … continuing the same process without interruption unless they encounter a catastrophic disaster like a volcano, tsunami, asteroid hit, nuclear explosion or the like.
That doesn’t sound anything like how a god or a vampire achieves immortality.
You’re right. As pointed out in Vice, some scientists prefer to call this "life cycle reversal" and compare it to a chicken forming a cyst that became an identical copy of the egg it came from. Or an old human forming a cyst that became an identical copy of themselves as a fetus, which then gestated somewhere for nine months before starting life all over again. In a way, the process is more like a living version of a Von Neumann universal constructor or self-replicating machine.
Call it what you wish … how do we get this immortality?
Good question … the same one the researchers at Universidad de Oviedo asked. To answer the question, they first needed to sequence the genome of the immortal jellyfish. Once that was accomplished – they identified a set of 17,468 genes – the researchers then sequenced the genome of a close relative of the T. dohrnii which did not have its immortality ability – the Turritopsis rubra. They also obtain gene sequences for some other species of jellyfish -- Hydra vulgaris, Clytia hemisphaerica, and Aurelia aurita. With all of that genetic data, they then began comparing the sequences to identify differences that might account for the unique biological immortality of the T. dohrnii.
“Specifically, our results suggest that gene amplification and point variants unique of T. dohrnii could affect its replicative efficiency, as well as DNA repair and telomere maintenance activity, which may be pivotal processes for cell rejuvenation and proliferation.”
In terms far beyond the pay grade of this writer, the study explains that the researchers narrowed their search to the genes involved in aging and DNA repair activities, and discovered that T. dohrnii was much better at replicating and repairing than all of the other species in the comparison. The “enhanced replicative capabilities in this species" was traced to T. dohrnii having more copies of the POLD1 and POLA2 genes, which encode different proteins, than their non-immortal relatives. They also found that T. dohrnii had “enhanced cellular plasticity" than in its mortal relatives, which "suggest enhanced replicative capabilities in this species." In other words, their cells stayed young longer, resulting in more opportunities to enter the “life cycle reversal.” Finally, they had more copies of the genes controlling DNA repair and telomerase, which is a specific feature which helps protect regions of chromosomal DNA from progressive degradation. In fact, they found that the genes in the immortal jellyfish didn’t just slow down the aging of the repair tools but actually enhanced and fine-tuned them.
That all sounds interesting, but did they figure out how humans can become immortal like these jellyfish? Does it involve eating them, because we hear they are delicious fried?
"We can't look at it as, hey, we are going to harvest these jellyfish and turn it into a skin cream."
Monty Graham, a jellyfish expert and director of the Florida Institute of Oceanography, who was not involved in the research, gave the bad news to Reuters – while the study is a giant leap forward in analyzing how the T. dohrnii achieves biological immortality while its closest relatives die their miserable jellyfish deaths, it doesn’t offer any help in extending the lifespan of humans or reversing the aging process.
Be that as it may, ‘The Immortal Jellyfish’ is still a great name for a band.