A species of jellyfish is known for its biological immortality, a characteristic that is more than rare in life. How does it work? It is by exploring its DNA, and comparing it with other species, that we can obtain the beginning of an explanation.
Turritopsis dohrnii is not just any jellyfish. She’s immortal—or at least her biological life cycle is the closest thing to it. It is born in the form of a larva (planula), which, once settled at the bottom of the sea, in turn gives rise to polyps, from which the jellyfish eventually detach. These polyps are however clones. And when T. dohrnii is in danger of death – old age, aggression, disease – it can return to the polyp stage, developing a new colony of clones.
We are therefore not talking about the eternal life of a single individual, strictly speaking, but about biological immortality, which has earned them the designation of “immortal jellyfish”. This life cycle is a kind of cellular rewind: each time it comes close to death, the jellyfish triggers the process of rejuvenation (it rejuvenates then redevelops via its colony of clones). In practice, there are some exceptions: the jellyfish can be eaten by a predator and does not escape certain fatal diseases when it is in the jellyfish stage.
Be that as it may, biological immortality is a thoroughly fascinating and little understood phenomenon. And, scientists are determined to unlock its secrets, as in a new study published on August 29, 2022. The authors compared the DNA of immortal jellyfish to that of deadly jellyfish, hoping that specificities emerge for Turritopsis dohrnii. More than 1,000 genes, linked to DNA repair and aging, thus served as a comparative basis.
How do immortal jellyfish escape death?
Exploring the DNA of a species makes it possible to seek explanations for its phenotypes, that is to say its apparent characteristics. In the case of Turritopsis dohrniiwe find, within its genetic code, elements of explanation of its phenotype of immortality.
The researchers were thus able to identify certain keys:
- The POLD1 and POLA2 genes are amplified, which “ suggests enhanced replication abilities in this species “, he reads in the study. This means greater genetic plasticity.
- In terms of DNA repair, the authors identified many copies of genes that are linked to it, in the immortal jellyfish, where these genes only exist in a single copy in the others.
- Same observation for telomerase, this biological process which slows down senescence (biological aging). There are more genes involved in telomerase in the immortal jellyfish, which could indicate ” that telomerase activity may be enhanced or more finely regulated in this species “.
” Taken together, this work provides a better understanding of the molecular mechanisms that give T. dohrnii the remarkable ability to rejuvenate and escape death. “, conclude the authors. But don’t expect any human application of these findings in the form of some recipe for immortality. This research serves above all to develop our knowledge of life.
