Turritopsis dohrnii, often called the immortal jellyfish, can revert sexually mature medusae back to an earlier polyp stage through cellular transdifferentiation, a rare form of life‑cycle reversal that allows individuals to escape death by ageing under certain conditions.
Life cycle reversal
Unlike most jellyfish that progress irreversibly from polyp to medusa, T. dohrnii can undergo reverse development: a damaged or senescing medusa transforms into a cyst that then produces new polyps, which can again give rise to medusae. This loop can, in principle, repeat multiple times, effectively enabling individuals to avoid senescence-related death.
Mechanism: transdifferentiation
The reversal depends on transdifferentiation, where specialised cells change identity and function to become different cell types rather than following a normal developmental pathway. This cellular plasticity, accompanied by complex gene‑expression changes and tissue remodelling, allows whole structures to be reorganised and regenerated.
Limits and real-world constraints
Calling the species truly immortal is an overstatement: individuals remain vulnerable to predation, disease and environmental hazards, and not every medusa will successfully revert. The phenomenon describes biological potential for repeated rejuvenation rather than absolute immunity to death.
Scientific significance
Studying T. dohrnii gives insight into cellular reprogramming, regeneration and the evolution of ageing; researchers examine genetic networks and molecular pathways that enable extreme plasticity with interest for basic biology and potential biomedical inspiration, while recognising important differences between cnidarian and human biology.
Takeaway
Turritopsis dohrnii’s ability to revert its life cycle is a remarkable example of biological plasticity: it can repeatedly return to juvenile stages via transdifferentiation, blurring conventional boundaries between development, ageing and regeneration while remaining ecologically vulnerable in nature.