Researchers have documented severed sea cucumber tissue continuing to grow and diversify for more than three years in ordinary seawater — a first-of-its-kind finding that could reshape what scientists thought was possible for tissue immortality and regeneration.
A routine observation on the seafloor has turned into one of the most surprising biological discoveries in recent memory. Scientists studying a cold-water sea cucumber species found that amputated tissue — simply discarded during experiments — didn’t die. Instead, it kept growing, reorganizing and showing signs of immune activity for more than three years in ordinary natural seawater.
The study, published May 27 in the journal Science Advances, was led by researchers at Memorial University of Newfoundland in collaboration with Bigelow Laboratory for Ocean Sciences. It marks the first documented case of long-term tissue survival and continued growth outside of a tightly controlled, sterilized laboratory environment.
What the Researchers Found
The team worked with Psolus fabricii, a cold-water sea cucumber species, conducting a series of experiments using tissue removed from the feet, main body and tentacles of three individual animals. The excised tissue was placed in flowing natural seawater — about the most biologically chaotic environment imaginable — rather than the sterile, bacteria-free conditions typically required to keep tissue cultures alive.
What happened next defied expectations. The tissue showed evidence of cell diversification, immune system activity and structural reorganization. With no mouth or digestive system to draw on, the cells appeared to absorb nutrients directly from amino acids dissolved in the surrounding seawater. The experiments ran for three full years before the team stopped them — not because the tissue had died, but because they needed to publish their results. Even at that point, the tissue remained active.
“Natural seawater is just about the most microbially diverse, least clean approach we could take experimentally,” co-author Sipler, a senior research scientist at the Bigelow Laboratory for Ocean Sciences, said in a news release. “Yet, that rich environment full of bacteria and all this organic matter was actually feeding them and allowing this tissue to heal and grow.”
Why This Challenges What We Know
Since the mid-20th century, researchers have worked with so-called immortal cell lines — the most famous being HeLa cells — that can reproduce indefinitely under laboratory conditions. But those cultures have always required axenic environments stripped of bacteria and other microorganisms. Even in those pristine settings, the tissue samples haven’t demonstrated actual healing, growth, or independent movement.
Sea cucumbers belong to the echinoderm phylum, a group already recognized for remarkable regenerative abilities and minimal cellular aging. But severed tissue was always assumed to eventually break down and die. What Sipler describes as a product of “keen observation” — noticing that discarded tube foot tissue hadn’t decayed after several weeks — set off a chain of experiments that rewrote those assumptions entirely.
Sipler used a striking analogy to describe just how far the findings push the boundaries of known biology.
“It’s like a lizard that loses its tail. We know some lizards can grow new tails; we’re talking about whether the tail can grow a new lizard,” she said.
Why It Matters for Students and Researchers
The implications stretch well beyond marine biology. Biomedical researchers and engineers could potentially use sea cucumber tissue as an accessible, low-barrier experimental model for studying everything from wound healing and anti-microbial responses to tissue regeneration therapies. Because sea cucumbers are invertebrates, they face far fewer regulatory restrictions than human-derived or vertebrate cell lines, making them easier to work with in settings that lack advanced biosafety infrastructure — including university labs with limited resources.
For students in biology, biomedical engineering or marine science, this kind of discovery signals a genuinely open frontier. The tissue’s ability to maintain structural complexity and continue growing in a messy, bacteria-rich environment makes it unlike anything currently used in cell culture research.
“This discovery highlights that the ocean holds profoundly unexpected biological innovations,” added Andrea Bodnar, the science director at the Gloucester Marine Genomics Institute, who was not involved in the study. “The fact that tissue explants from a sea cucumber can heal, reorganize, and survive independently for years in natural seawater suggests an entirely new model for biological resilience and tissue regeneration.”
A Reminder of the Ocean’s Untapped Potential
For Sipler, the discovery is also a call to action around ocean conservation. Countless species remain unstudied, and the biology hidden in the world’s oceans could yield breakthroughs researchers haven’t yet imagined.
“The best advances in science are made when you find a natural analog for what you’re studying,” Sipler said. “Here is this species that has this groundbreaking ability, and we had no idea. It’s a reminder how much is yet to be discovered in the marine environment, and how important it is to protect these resources that may hold really valuable knowledge for us.”
The research team has not yet grown a complete new sea cucumber from explanted tissue, but Sipler noted that the cellular growth and diversification observed already represents something extraordinary. As experiments continue, scientists hope to understand the precise biological mechanisms that allow this tissue to persist — and potentially harness them for human medicine.