What can we learn from the immortal jellyfish?

If we could live forever, would you want to anyway?

Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual

Gather ye rosebuds while ye may, Old Time is still a-flying:

And this same flower that smiles today Tomorrow will be dying

— Robert Herrick

When our species developed big brains, we made the devastating discovery that death is inevitable. Within a few decades at most we, and everyone we know and love, will be gone with the wind. In Jean-Paul Sartre’s words "man is a useless passion".

Philosophers, poets, and religious mystics have tried to address the problem. Now it’s the turn of scientists, although longevity, rather than eternal life, is their focus.

But is it wise to keep the grim reaper at bay indefinitely?

Immortality: The quest to live forever and how it drives civilisation. By Stephen Cave

Stephen Cave of the Cambridge Institute for Technology and Humanity is not so sure. Interviewed on the BBC World Service last week, he questioned whether it’s possible to prolong our lives eternally — and if it is, he asked, should we do so?

Some wild creatures have managed to answer the first of these questions, at least partially. The life expectancies of bats, for example, are many times greater than those of similarly-sized mammals. A bat raises only one offspring each year, whereas a mouse, with up to 14 pups per litter, can parent almost 60. Bats, therefore, had to evolve longevity in order to avoid extinction.

Greenland sharks measure their lifespans in centuries and 200-year-old Inuit arrowheads have been found embedded in the flesh of bowhead whales. Some reptiles live to a great age, although claims that Jonathon, a 191-year-old giant tortoise, chatted with Napoleon on St Helena are certainly apocryphal. The tortoise only arrived on the island in 1882, whereas Bonaparte had died in 1821. The Oscar for the longest animal lifespan known to science goes to a much more humble creature, the aptly-named ‘immortal jellyfish’.

Turritopsis dohrnii is a remarkable creature. Immortal jellyfish specialist, Shin Kubota of Kyoto University, composed a song about it, which he sings at the end of his conference presentations.

Dohrnii featured also in the children’s TV cartoon series Octonauts, which I watched with my grandchildren on Youtube.

This Methuselah of the animal kingdom begins life as a tiny free-swimming larva in temperate and tropical seas throughout the world. Lodging on the sea bottom, it produces a community of identical polyps. In due course, polyps detach and begin a free-swimming stage. Becoming sexually mature, each develops a medusa up to 4cm in diameter. Adults, with up to 90 tentacles, live on plankton. When a dohrnii faces adversity, however, it doesn’t keel over and die. Instead, it reverts to its polyp form and starts life from that stage all over again. There is no limit, in theory, to the number of reincarnations the jellyfish can undertake but, eventually, disease predators and sudden temperature changes will put an end to its gallop.

No longer a spring chicken myself, I find Cave’s second question troubling. Like our present two-tier health services, will only the rich and powerful be able to access longevity technology? Will affluent oldies, lingering on in an increasingly crowded world, become a serious drain on scarce medical resources?

Is it my duty to die?

• Stephen Cave. Immortality: The Quest to Live Forever and How it Drives Civilisation. 2017