…Some animal are immortal?
Theoretically, that is—or, at least, they do not age. Obviously, they can die from other causes: accidents, predators etc. I found this bit of arcana fascinating and thought I’d share.
One species that has been called ‘biologically immortal’ is the jellyfish Turritopsis dohrnii. These small, transparent animals hang out in oceans around the world and can turn back time by reverting to an earlier stage of their life cycle.
Then there is the Hydra: a tubular body with a tentacle-ringed mouth at one end and an adhesive foot at the other. They’re very simple animals that spend their days mostly staying in one place in freshwater ponds or rivers and using their stinging tentacles to grab any prey that happens to swim past. Their claim to immortality? They don’t go through senescence (biological aging) at all. Instead of gradually deteriorating over time, a Hydra’s stem cells have the capacity for infinite self-renewal. Cool, right? However, who’d want to be a Hydra…
Lobsters also do not experience senescence. Unlike Hydra’s reliance on particular genes, however, their longevity is thanks to them being able to endlessly repair their DNA. Unfortunately there’s a catch: they literally grow too big for their own shells. Lobsters continually grow larger and larger, but their shells can’t change size, meaning a lifetime of ditching too-small shells and growing a brand-new exoskeleton each time. That takes a fair amount of energy. Eventually, this becomes too much, and they die of exhaustion—unless they have managed to end up in a lobster roll before that happens.
Many other species offer tantalising glimpses into an ageless existence: such as naked mole rats, whose risk of dying does not increase as they get older; the Ming quahod clam; some bristlecone pines—there is a colony of quaking aspens considered to be about 80,000 years old. Also the enormous bowhead whale, which can live up to 200 years, since they can repair damaged DNA, hence are prevented from developing cancer. Scientists also suggested that these whales can survive the absence of oxygen even for a long time.
These animal can perhaps provide information which will benefit human longevity. But to the question, asked by a young relative, ‘Would you like to live forever?’ my answer is, ‘No, thank you.’ Especially if I had to live attached to a rock, like a Hydra.
Letters from Athens 