One species of jellyfish has no lifespan limits because it can manipulate its cells. Unique biological process - Transdifferentiation - Extinct frog rediscovered
Jellyfish, which are an invertebrate species, are the most plentiful Earthlings on the planet today. That means that if aliens visitors were to conduct an objective survey, pound for pound, they would have to conclude that this was a jellyfish world. Now scientists have determined that not only are they the most plentiful creatures on Earth, one species of jellyfish has found a way to live indefinitely. It may be "immortal," but it certainly does not live forever: Seas dry up, the planet goes through tremendous upheavals, with the entire world-system passing through phases of apocalyptic dissolution, chaos, and evolution.
Few people appreciate that there are repeatedly (cyclically) times when the average human lifespan increases to tens of thousands of years. Lifespans are not uniform over time in any realm; higher (deva) worlds may always have greater longevity, but it's relative. So to think that we are at much of an advantage because "we are living longer" now than a few years ago is ironic to the point of being absurd.
Nevertheless, the rebirth process ensures that, conventionally-speaking, we already live indefinitely. Meanwhile, the doctrine of impersonality (anatta) of phenomena ensures that, ultimately-speaking, we do not persist for two consecutive moments. The mark of phenomenal objects is that they are radically impermanent, impersonal, and unsatisfactory. But don't tell the jellyfish as they frolic in the sea never being eaten, suffering from global warming, or being dismayed by the environmental degradation that comes from floating next to pools of plastic trash.