The Jellyfish that (theoretically) Never Dies
Are there really immortal jellyfishes? Could they hold the key to human immortality? To answer your question, yes, they exist. Turritopsis dohrnii, or the Immortal Jellyfish as they are commonly known, have been known to be able to revert back to a young, immature stage of their life cycle when they grow old. This is an ability unique to them alone in the animal kingdom. Though there are other animals that are biologically immortal as well, like lobsters, there is a debate in the scientific community over whether they really are or not, since the oldest lobster found was 140 years old and no others have been found anywhere close to it. Though it has been getting increasingly apparent that they really are biologically immortal, its just the exhaustion from having to shed an old shell that kills them other than us eating them.
Essentially, every jellyfish has three stages in its life. It starts off life as a planula, which, on finding favourable conditions, becomes a polyp, those things with thick hair at the ocean floor, then grows to become a sexually mature medusa, the signature jellyfish shape. Then they reproduce and die, and their offspring carry on the whole process. But Turritopsis dohrnii jellyfishes don’t. When injured, old or sick, they revert back to the planula stage in a process over a period of three days. First their tentacles and bell deteriorate and form a cyst. This, over two days, becomes a planula again and it floats off to find a good spot to restart its life.
The reason this happens is because of an enzyme called telomerase. Basically, the chromosomes of every cell have many repetitive DNA sequences i.e. TTAGGG at their ends which act as a protective cap. Whenever the cell divides (50-70 times during its life), a few sequences are lost. Instead of losing precious genes, telomeres martyr themselves for the greater good. But eventually, the case of ‘They protect us, but who’ll protect them?’ comes up, and the telomeres get too short to protect the DNA. The cell falls into a sort of a coma called senescence, cluttering and degrading organs. This then results in the cell dying, or, in fancy words, apoptosis.
This is where telomerase comes in. Telomerase adds more sequences to telomeres, maintaining their length. Thus, cells can keep dividing and the organism never ages. But though active telomerase isn’t very common in somatic cells, they are in higher concentrations in germ cells, simply because they use it more. As a result, your somatic cells age and die, with you following.
Scientists are searching for a way to extract, control and mass produce this enzyme to increase longevity. Cells with enough telomerase keep dividing uncontrollably causing tumors and cancer; tumors have found a way to activate the inactive telomerase in somatic cells and achieve immortality.
At Kyoto University, Japan, Professor Shin Kubota’s carefully nurtured Turritopsis dohrnii and observed more than 11 successful transdifferentiations in more than two years of captivity.
And that’s it for these fascinating creatures, people. No brain, no complex organs, 90% water, yet have a rather clever way of communicating, have cool stun guns, can glow in the dark, are immortal, and have been around for many more years than us. We, the apparent ‘evolved and biologically superior beings’ have much to learn from these serene organisms.