The hydrozoan Turritopsis dohrnii, an animal about 4.5 millimetres wide and tall (likely making it smaller than the nail on your little finger), can actually reverse its life cycle. It has been dubbed the immortal jellyfish.
When the medusa of this species is physically damaged or experiences stresses such as starvation, instead of dying it shrinks in on itself, reabsorbing its tentacles and losing the ability to swim. It then settles on the seafloor as a blob-like cyst.
Over the next 24-36 hours, this blob develops into a new polyp - the jellyfish's previous life stage - and after maturing, medusae bud off. This phenomenon has been likened to that of a butterfly which, instead of dying, would be able to transform back into a caterpillar and then metamorphose into an adult butterfly once again.
The process behind the jellyfish's remarkable transformation is called transdifferentiation and is extremely rare.
Medusa cells and polyp cells are different - some cells and organs only occur in the polyp, others only in the adult jellyfish. Transdifferentiation reprogrammes the medusa's specialised cells to become specialised polyp cells, allowing the jellyfish to regrow themselves in an entirely different body plan to the free-swimming jellyfish they had recently been. They can then mature again from there as normal, producing new, genetically identical medusae.
This life cycle reversal can be repeated, and in perfect conditions, it may be that these jellyfish would never die of old age.
'We might be distracted watching much larger jellyfish, but the tiny things such as this can inform so much of our science about these animals,' says Miranda.
The hydrozoan Turritopsis dohrnii, an animal about 4.5 millimetres wide and tall (likely making it smaller than the nail on your little finger), can actually reverse its life cycle. It has been dubbed the immortal jellyfish.
When the medusa of this species is physically damaged or experiences stresses such as starvation, instead of dying it shrinks in on itself, reabsorbing its tentacles and losing the ability to swim. It then settles on the seafloor as a blob-like cyst.
Over the next 24-36 hours, this blob develops into a new polyp - the jellyfish's previous life stage - and after maturing, medusae bud off. This phenomenon has been likened to that of a butterfly which, instead of dying, would be able to transform back into a caterpillar and then metamorphose into an adult butterfly once again.
The process behind the jellyfish's remarkable transformation is called transdifferentiation and is extremely rare.
Medusa cells and polyp cells are different - some cells and organs only occur in the polyp, others only in the adult jellyfish. Transdifferentiation reprogrammes the medusa's specialised cells to become specialised polyp cells, allowing the jellyfish to regrow themselves in an entirely different body plan to the free-swimming jellyfish they had recently been. They can then mature again from there as normal, producing new, genetically identical medusae.
This life cycle reversal can be repeated, and in perfect conditions, it may be that these jellyfish would never die of old age.
'We might be distracted watching much larger jellyfish, but the tiny things such as this can inform so much of our science about these animals,' says Miranda.
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