Arguably the most well-known invertebrate in the world, jellyfish earn their renown from their ethereal presence and their massive populations. Rumors abound about this sea creature’s lifespan. Do immortal beings really populate our seas? It seems like there are hundreds of thousands in every ocean in the world, washing up on beaches from California to Namibia to Japan.
Can they live forever?
The Turritopsis dohrnii is more commonly referred to as the immortal jellyfish.
It is the only species of jellyfish (or of any multi-celled animal) so far proven to live up to its name.
Members of this species can rejuvenate themselves better than slapping on some anti-aging cream: they actually override the natural aging process.
The jellyfish in the grown medusa state changes its cells back to the polyp, or adolescent, state. They avoid death by reverting back to their juvenile state, essentially starting over. The process, called transdifferation, gives the invertebrate a new lease on life – literally!
Craziest of all, it’s a perpetually renewable lease. Scientist theorize that the immortal jellyfish could do this indefinitely, hence its appropriate name.
Scientists have observed that these jellyfish resort to transdifferation when faced with dangerous changes in their environment (such as a reduction in salinity of the water or a drastic temperature change) or a threat to their wellbeing (such as starvation or physical damage to their bell).
It doesn’t have to be a threatening situation to force their hand – or tentacle, if you will.
Time itself will lend to the process of transdifferation. Simply facing old age will inspire the process.
Scientists have yet to study this in the wild, though, so all evidence comes from laboratory experiments.
Of course, being immortal doesn’t mean that you’re indestructible. Even majestic creatures such as the immortal jellyfish are subject to the dangers of the natural world. Predators and disease can strike these small jellies, effectively ending their never-ending life cycle for good.
Jellyfish reproduce by a variety of methods.
They can increase their population sexually, asexually, by budding, or by a mitosis-like process in which the jelly actually splits into two.
A very cool and slightly terrifying fact, some jellyfish can reproduce posthumously. In 2011 in China, a marine biology student witnessed new polyps forming out of a moon jellyfish that had been dead for several months.
Rising from the grave, these polyps would go on to develop into medusas: fully grown adult jellyfish.
This form of reproduction might be debatable in terms of immortality and seem more like a zombie uprising. Regardless, we can’t doubt that jellyfish are fantastical creatures.
Aside from lesser, single-celled organisms and flora, the immortal jellyfish is the only fauna on Earth known to be immortal.
There are a variety of animals with incredibly long lifespans, but none of which are everlasting.
Lobsters are commonly mistaken to be immortal. Their average lifespan is only 40 to 50 years (though it is hard to precisely age a lobster) and they do perish from natural causes, making them very mortal.
The reason people think otherwise is because they are biologically immortal, meaning that they do not age the same way we do. They do not have a chronological lifespan, broken down into childhood, adolescence, and adulthood. They do not slow down with old age or lose fertility like many other species.
They do, however, eventually die because they stop moulting and their exoskeleton degrades or from exhaustion.
Old age seems to go hand-in-hand with the ocean. A range of coral, mollusks, and sea sponges are known to live for hundreds if not thousands of years.
More impressively, if a 2016 study is correct, a specific Greenland shark could be as old as 512 years! That would mean that the shark in question was born the same year Henry VIII became king of England. Until proven, their average lifespan is 300 years.
Although crocodiles are not immortal, they do not die of traditional old age and can live extremely long lives.
The best thing to take away from these immortal sea creatures is the inspiration they give scientists for human application. The potential to use human stem cells to renew dead or damaged human tissue is given hope by this exact, naturally occurring event in the animal kingdom.
Sources:
https://www.nationalgeographic.com/magazine/2018/10/jellyfish-species-reproduction-feeding-ocean/
https://www.smithsonianmag.com/science-nature/jellyfish-the-next-king-of-the-sea-679915/
https://en.wikipedia.org/wiki/Turritopsis_dohrnii
https://en.wikipedia.org/wiki/List_of_longest-living_organisms
https://www.bbcearth.com/blog/?article=the-jellyfish-that-never-dies
