Science with Dr Karl: Immortal Jellyfish!

Can these creatures live forever?!

There have always been myths about immortality, the ability to live forever. But is it possible? Well, marine biologists have found a creature that comes close – a tiny, transparent jellyfish.

WHAT ARE THEY?

While it has the unofficial name of ‘immortal jellyfish‘, its official name is Turritopsis dohrnii (it used to be Turritopsis nutricula).

After an adult male T. dohrnii squirts his sperm into the ocean waters, some of them end up inside a female. This creates fertilised eggs, which then turn into tiny, free-swimming larvae called “planula”.

After a while, the planula give up swimming and dive down to the sea floor, where they attach themselves to a rock. They then change shape entirely into columns of highly branched polyps. After a few days, another change of shape happens. Tiny jellyfish (about 1mm across) “bud” off from the tips of the polyp and, like miniature umbrellas with tentacles, float through the ocean.

After 2-4 weeks, they become sexually mature males or females. They’re about 5mm across, with a bright red stomach visible through their transparent body. They eat plankton, tiny molluscs, larvae and fish eggs.

CAN THEY LIVE FOREVER?

Now T. dohrnii jellyfish can be eaten by bigger creatures – so they are not truly immortal.

But when this cool jellyfish suffers a physical attack, or starvation, or some kind of environmental stress, instead of dying, they change firstly into a tiny blob, and then back to the polyp stage within 3 days. They become another polyp colony sitting on a rock. The polyp is genetically identical to the original jellyfish – but is packaged differently.

Did that original jellyfish die? Not really. But did that original jellyfish continue to live in the same body? No. It’s kind of like a butterfly that instead of dying changes back to a caterpillar – or an aged chicken turning back into an egg.

So technically it’s more like “regeneration” – but it’s the closest that we have to immortality. And once scientists learn how T. dohrnii does it, they could apply this knowledge to medical science for humans.