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Sep 27

Bizarre Animal of the Week: Immortal Jellyfish

The key to eternal life has, quite possibly, been found – by a tiny gelatinous jellyfish. A transparent brainless blob seems an unlikely candidate to have made such a revolutionary discovery, but it has an amazing ability: it can start its life anew.

The immortal jellyfish, as it is called, can reboot its very existence if it is injured or faces starvation. First, the medusa – the domed, free-swimming adult that we normally associate with jellyfish – turns itself inside out, and then its innards start to disintegrate into cellular liquid. As it absorbs its beating tentacles, it loses the ability to swim and falls to the seabed. Shortly afterwards, from the blob of recycled cells sprouts a polyp, the tiny anemone-like jellyfish larva. And so the animal has been reborn.

The Immortal Jellyfish

Photo: Takashi Murai

The immortal jellyfish is the first (and so far only) animal which, upon having first reached sexual maturity, is capable of reverting back to its immature form – metamorphosis, but in reverse. It’s like your grandfather melting down and morphing back into a newborn baby. Whereas other animals can undergo metamorphosis, they can only rearrange what they have already got (see my previous article here for how metamorphosis actually works). The immortal jellyfish, however, orchestrates an organism-wide transformation of cells; muscle cells, for example, are capable of changing into skin cells without too much difficulty.

Can this cycle continue indefinitely? Are there any limits? At the moment, we just don’t know. In the wild, the immortal jellyfish is unlikely to achieve any great age because it will eventually succumb to predation or disease. And in captivity, research is still being conducted. The fact of the matter is that we haven’t studied this intriguing creature for long enough to learn much more about this amazing ability. Only time will tell as to how a tiny primitive animal that seems capable of completely bypassing death will affect the world.

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