These sea cucumbers seem to have ‘zombie’ flesh that doesn’t die when lopped off

A Canadian scientist has found that amputated bits of flesh cut from scarlet sea cucumbers can carry on for years in a strange new form, somewhere between life and death.

Sara Jobson is a doctoral student in the ocean sciences department at Memorial University in Newfoundland and Labrador, where she led the study that discovered what appears to be immortality of the sea cucumber’s tissue.

Jobson said she and her colleagues have spent several years observing their “little lab zombies” in what is said to be the first known case of severed tissue surviving on its own.

“Is it alive? It’s not reproducing, it’s not regrowing into [another sea cucumber], but it’s not dead,” she said in a recent interview. “It seems that they’re able to reform into a new biological unit, in a way.”

Typically, if someone lops off a chunk of flesh from an animal, the tissue will die — and it will be pretty obvious that it’s dying, Jobson said. But things are different for the scarlet sea cucumber, or psolus fabricii, which is found in the North Atlantic Ocean.

For a study published recently in the journal Science Advances, Jobson and her team placed pieces of a scarlet sea cucumber’s tentacles and tube feet in sea water to watch what happened.

The chunks of flesh appeared to begin sterilizing the amputation site by getting rid of any degrading tissue. Then the edges of the cut curled in to seal off the wound from the environment, Jobson said.

Slowly, over the next few years, the tissue grew into perfectly round translucent blobs, with a nucleus of red pigment in their centres, she said.

“That’s the crazy part, it’s not becoming a new sea cucumber,” Jobson said. Instead, the tissue samples had somehow grown into “a new biological unit” and they simply stayed that way, she said.

They absorbed nutrients, they had an active immune system to protect themselves from bacteria, all of which would classify them as living organisms. But unlike living things, they didn’t reproduce, she said.

“And that’s where we got the term ‘zombie tissue,”‘ she said. “Our little lab zombies are on that line between life and death, and what does it mean?”

It’s also not clear how this might offer any evolutionary benefit to the sea cucumbers, Jobson added.

Aside from the deep questions posed by her work, Jobson said having access to hardy tissue samples that survive on their own could open a lot of opportunities in scientific research. She hope to keep investigating the bizarre little blobs, particularly to determine if their cells are aging.

Jobson credited her discovery in part to the kind of “curiosity-driven science” supported by the lab she worked in, which is run by Annie Mercier, a professor of ocean sciences at Memorial University.

“When we don’t provide people the opportunity to ask really weird, out-of-the box questions, we don’t get these cool answers,” Jobson said.

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