There are numerous species in the animal kingdom that can regrow not only tissue but entire limbs.
The best-known examples include lizards that grow back their tails and starfish that can grow new arms. But many other species are also capable of remarkable regeneration.
The ability of flatworms to repair and regenerate themselves is truly astonishing. If you dice a flatworm in any way, each fragment will, over time, become a fully functioning creature. How flatworms do this is not fully understood, but it is a trait that has earned them the fame of being, in the words of 19th-century naturalist John Graham Dalyell, “immortal at the edge of a knife.”
The axolotl, for example, is known not only for its ability to regrow missing limbs and tail, but also its jaw, heart and parts of its brain. If paralyzed, it can even grow new neurons and neurological connections, allowing it to walk again.
And then there’s the immortal jellyfish, which, like at least five other species of jellyfish, avoids death by pressing rewind. Even after a dead jellyfish collapses into a pile of mush, its cells can grow into polyps.
It is like a piece of a butterfly’s wing turning into a caterpillar.
Immortal jellyfish can still die from predators and disease, but their ability to regenerate makes them resilient and successful.
However, the price for the renewal must be Hydractinia – tiny predators related to jellyfish and corals.
They are also known as “snail hair” and are nibbled on by fish swimming past. Their tentacled heads are the usual target. Losing the head is not a problem, however – the animals simply grow new heads.
The key to HydractiniaThe regenerative ability of animals is that they retain their embryonic stem cells throughout their lives. These cells can be “recalled” when needed to form new body parts.
