Sea cucumber scraps survive for years, baffling scientists

Amputated tissue from the sea cucumber Psolus fabricii keeps living for more than three years in seawater tanks, repairing wounds and continuing to grow without becoming new organisms. Researchers call it biologically immortal, though experts warn the evidence

On the first day the sea cucumber tissue is cut away, it looks like loss—just fragments left behind. But in a set of lab observations. pieces from Psolus fabricii kept moving. healing. and growing in natural seawater for more than three years. The results are pushing researchers to use a word most biology papers avoid: immortality.

After tracking amputated tissues that survived in natural seawater tanks for more than three years. researchers declared them biologically immortal in a paper published today in Science Advances. Lead author Sara Jobson. a doctoral student at Memorial University of Newfoundland. called the finding unprecedented: “Something like this has never been seen before.”.

The experiments weren’t simply about survival. The severed tissue repaired its wounds and continued to grow, even though it didn’t regrow into a new organism. Jobson compared the effect to something startlingly life-like: “as if the tail dropped off and healed and wiggled around in the wild on its own.”.

Sea cucumbers are already known for regeneration. but Jobson emphasized that many other animals—lizards and salamanders among them—still deteriorate after detachment. In those cases, detached limbs and tails decay much like human tissue does. With P. fabricii, the detached tissues appear to stay in a different category altogether.

The team doesn’t have one single explanation, but they offered clues about what may be keeping the fragments going. The severed tissues retain a strong immune system and chemical defenses against microbial infection. Their cells keep dividing to form new tissue. And to fuel that ongoing activity, the tissues either absorb dissolved amino acids or cannibalize their own muscle.

Still, Jobson said the biology sits in a gray zone that’s hard to name. “We often call them, lovingly, our little lab zombies,” she said. “Because we don’t know: Do they count as alive?. Do they count as dead?” The fragments don’t reproduce, and they don’t have a mouth or a gut. Yet they endure as complex living structures separated from the original organism—potentially for a very long time.

Jobson reported no signs of the tissue degrading. “We haven’t seen any signs that they’re degrading or dying,” she said.

But immortality—biological immortality in particular—doesn’t persuade everyone on the first try.

Alejandro Sánchez Alvarado. a molecular biologist and president of the Stowers Institute for Medical Research in Missouri. said it’s “quite likely premature” to declare that these tissues will live forever. To make a stronger case. researchers would need to test whether the tissues’ telomeres—the DNA sequences at the end of chromosomes that shorten with age—stay the same length after many rounds of cell division. Sánchez Alvarado also offered a more precise kind of admiration for what’s already clear: “what is remarkable here is not infinite time per se but the sustained coordination” of many biological processes for so long in the discarded parts of an animal.

Even with the caution, the gap between this tissue and ordinary detachment is hard to ignore. The most extreme longevity in the study outlasted other sea cucumber species’ severed tissue by a wide margin. The “silver medalist” perished before three and a half months, while the P. fabricii fragments survived for more than three years.

That longevity also creates an evolutionary puzzle. If reproduction is a core imperative of life, why would nonreproductive scraps remain viable for years?. Jobson said the lack of obvious purpose complicates the story: “It doesn’t regrow into a new sea cucumber. as far as we can tell. ” she said. adding that “the purpose of it is very unclear.” One possibility is that the behavior may simply be a by-product of P. fabricii’s exceptional regenerative capacity.

So where does that leave the strange idea of “zombies” drifting through the oceans? Jobson believes that whatever these fragments are—immortal or slowly succumbing, purposeful or accidental—they could already exist in the wild. “Maybe,” she said, “there’s a ton of zombies out there.”

sea cucumber Psolus fabricii regeneration biological immortality Science Advances telomeres immune system microbial defenses cellular division