The "immortal jellyfish" can rewind its own life cycle
When stressed, this tiny jellyfish doesn't die — it reverts to a juvenile and starts over.
Most animals run their life cycle one way: birth, maturity, death. Turritopsis dohrnii, a jellyfish barely 4.5 millimetres across, can run it backwards.
When the adult medusa is injured, starved, or hit by a sudden change in temperature or salinity, it can collapse into a blob, settle to the seafloor, and grow back into a polyp — the immature colonial stage it came from. The reborn colony then buds off new, genetically identical medusae.
The trick is transdifferentiation: already-specialised cells switch directly into completely different cell types, effectively resetting the body’s clock. In the lab this reprogramming can happen in about 24 hours.
Because the cycle can repeat indefinitely, the animal is described as biologically immortal.
It is not truly deathless — predators and disease still kill it constantly — but its cellular reset makes it a prized model for research into ageing and regeneration.
Sources & references
2 referencesWell-established. Corroborated by 2 independent sources.
