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<\/a>Psolus fabricii. Image credits: Rebecca Evans\/Wikimedia Commons<\/a><\/p>\nDetached body parts<\/a> from a sea cucumber called Psolus fabricii not only survived after being separated from the animal but also healed themselves, absorbed nutrients, and continued living for more than three years.<\/p>\n \u201cThese findings challenge our basic understanding of tissue resilience and degradability,\u201d the researchers note<\/a> in their study.<\/p>\n<\/blockquote>\n Biologists have known that some animals can regrow lost body parts<\/a>. Salamanders can famously regenerate limbs, sea stars can regrow arms, and, while we\u2019re at it, many sea cucumbers can rebuild damaged organs.\u00a0<\/p>\n However, the detached body parts themselves were generally assumed to wither and die. This newly discovered tissue appears to follow a different set of rules.<\/p>\n An accidental discovery<\/p>\n The discovery began unexpectedly in a laboratory at Memorial University in Canada. Researchers were keeping live Psolus fabricii sea cucumbers in aquariums<\/a> when they noticed that some tube feet (the small appendages the animals use to grip surfaces) had been left behind on the tank walls after the animals were removed.<\/p>\n At first, the observation did not seem unusual. Sea cucumbers can voluntarily shed tube feet when threatened and later regrow them. What surprised the researchers was that days turned into weeks, and weeks turned into months, but the detached appendages did not die. The tiny body parts remained attached to the glass and appeared to be healing.<\/p>\n To investigate further, the team collected tube feet, tentacles, and other tissue fragments from the animals and monitored them in flowing natural seawater. <\/p>\n Unlike most tissue-culture experiments, the samples were not kept in sterile laboratory conditions. Instead, they were exposed to seawater filled with bacteria, microorganisms, and organic matter, closely resembling their natural habitat. The results surprised the researchers.<\/p>\n \u00d7<\/p>\n Thank you! One more thing…<\/p>\n Please check your inbox and confirm your subscription.<\/p>\n \u201cWe report the first known case of long-term survival and growth of discarded complex tissues in a natural setting,\u201d the study authors note.<\/p>\n<\/blockquote>\n How the detached tissues fed themselves<\/p>\n The researchers used a suit of techniques, including microscopy, tissue staining, cell growth measurements, and nutrient-tracking experiments, to determine whether the tissues were truly alive and how they survived.<\/p>\n They found that within days of being detached<\/a>, the tube feet began repairing damaged tissue. Wounds closed, immune cells gathered around the injury sites, and the tissues showed active cell division.\u00a0<\/p>\n At the same time, old or damaged cells were being removed through programmed cell death, a process commonly seen in healthy living tissues. The fragments also demonstrated an ability that seemed almost impossible. Despite having no mouth, digestive system, or circulatory system, they continued acquiring nutrients from their surroundings.<\/p>\n To test this, the team added nitrogen-labeled amino acids<\/a> and ammonium compounds to seawater containing the detached tissues. The experiments showed that the tissues absorbed nutrients directly from the water and used them to support growth and repair.<\/p>\n Over the following months, the detached tube feet underwent dramatic changes. The original foot-like structures gradually became rounded masses of living tissue. After shrinking initially, they recovered their size and eventually grew larger than they had been when first detached.<\/p>\n More than three years after separation, the tissues still showed no obvious signs of decay or collapse. They continued responding to touch, producing new cells, and maintaining active immune defenses.<\/p>\n \u201cAs far as we can tell, there weren\u2019t any signs of death, degradation or necrosis,\u201d Jobson said.<\/p>\n<\/blockquote>\n More importantly, the tissues never regenerated into complete sea cucumbers. Instead, they entered what appears to be a stable, self-sustaining state somewhere between a conventional tissue sample and an independent organism. The researchers named these structures LiPfe (living immortal Psolus fabricii explants).<\/p>\n \u201cWe lovingly call these tissue explants \u2018our zombies,\u2019 because they seem to ride the line between dead and alive,\u201d Jobson said.<\/p>\n<\/blockquote>\n A one-of-a-kind ability<\/p>\n When the team tested tissues from other echinoderms\u2014including sea stars, sea urchins, brittle stars, and other sea cucumber species\u2014none matched the long-term survival seen in P. fabricii, suggesting the phenomenon may be unique.<\/p>\n \u201cLiPfe demonstrate an ability to heal and regenerate through ongoing cellular processes (mitosis and apoptosis), defend themselves with an active immune system (coelomocytes), maintain metabolic function (through nutrient absorption), and progressively alter their phenotype,\u201d the study authors explain.<\/p>\n<\/blockquote>\n According to the researchers, the system could provide a new model for studying regeneration<\/a>, tissue repair, immune function, aging, and long-term tissue survival.\u00a0<\/p>\n \u201cThese findings open the door to a new class of experimental models, free from ethical concerns, which bridge evolutionary biology with translational research in healing, longevity, and biocompatibility,\u201d the researchers added.<\/p>\n<\/blockquote>\n The discovery may also help scientists understand how living tissues resist infection and maintain themselves in microbe-rich environments.\u00a0<\/p>\n However, some big questions remain unanswered. For instance, the researchers still do not know whether the tissues are truly immortal<\/a> or simply extraordinarily long-lived. They also do not yet understand the molecular mechanisms that allow the detached tissues to survive for years.<\/p>\n Hopefully, further research will reveal the answers to these questions.<\/p>\n\n
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