'Astonishing': Scientists discover animal you can cut into three pieces, and every piece will regrow into a new animal

Scientists in Israel have made an "astounding discovery" - a creature not too far from humans on the tree of life that can regenerate every single organ of its body after being cut into pieces.

Each remaining piece regrows everything it needs to live - whether it's a digestive system, nerve centre or a heart. 

Polycarpa mytiligera, a type of marine animal better known as an ascidian or a 'sea squirt', was first discovered in the early 1800s. Until now the extent of its incredible regenerative abilities were unknown, and are completely unheard of in chordate animals - basically, those with a spinal cord of sorts, which includes humans. 

"The ability to regenerate organs is common in the animal kingdom, and even among chordates you can find animals that regenerate organs, like the gecko who is able to grow a new tail," said Noa Shenkar of Tel-Aviv University.

"But not entire body systems. Here we found a chordate that can regenerate all of its organs even if it is separated into three pieces, with each piece knowing exactly how to regain functioning of all its missing body systems within a short period of time."

Polycarpa mytiligera, found in the coral reefs of the Red Sea town of Eilat, are considered "the closest to humans from an evolutionary point of view" among invertebrate creatures - those without a backbone.

"There are species of ascidians that perform simple regeneration in order to reproduce," said Gordon. "These are species with a colonial lifestyle, with many identical individuals connected to one another. They replicate themselves in order to grow. 

"In contrast, the ascidian from Eilat, Polycarpa mytiligera, is an organism with a solitary lifestyle, without the capacity for asexual reproduction, similar to humans."

Polycarpa mytiligera
Polycarpa mytiligera. Photo credit: Tel Aviv University

Previous research has found that like geckos, Polycarpa mytiligera can regenerate a lost organ. But the new study found they're capable of much more than that. 

"We dissected several dozen ascidians into three fragments, leaving a part of the body without a nerve centre, heart, and part of the digestive system," said Gordon. 

"And contrary to our expectations, not only did each part survive the dissection on its own, all of the organs were regenerated in each of the three sections. Instead of one ascidian, there were now three. 

"This is very astonishing. Never before has such regenerative capacity been discovered among a solitary species that reproduces sexually, anywhere in the world."

Contrary to what many of us heard on the playground as kids, cutting a worm in half doesn't make two worms - there's a chance the end with the head will survive, but the bottom half quickly dies. 

Prof Shenkar said the finding could "help the human race" find ways to regenerate lost limbs - something we can't do at all, let alone grow new organs from scratch. 

"Since the dawn of humanity, humans have been fascinated by the ability to regenerate damaged or missing organs. Regeneration is a wonderful ability that we have, to a very limited extent, and we would like to understand how it works in order to try and apply it within our own bodies."

The study, And Then There Were Three… Extreme Regeneration Ability of the Solitary Chordate Polycarpa mytiligera, was published this week in journal Frontiers in Cell and Developmental Biology.