It came from a creature of the depths. A severed foot that refused to die, regenerating in an act of survival unlike anything we’ve ever seen.
It could be a great opening to a horror novel (agents, call me), but to researchers from Memorial University and the Society for Exploration and Valuing of the Environment in Canada, this discovery of a “real-life zombie” is no work of fiction.
“Here is this species that has this groundbreaking ability, and we had no idea,” says Memorial University marine biogeochemist Rachel Sipler, who is also a senior researcher at the Bigelow Laboratory for Ocean Sciences. “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.”
Found in the cold-water regions of the Atlantic and Arctic oceans, the dendrochirotid sea cucumber Psolus fabricii already resembles a living nightmare. Branches of blood-red tentacles blossom from one end of a fleshy, scale-covered body, beneath which numerous tube feet carry it around the ocean floor, no doubt just to terrify baby fish into staying in bed at night.
Being relatively soft creatures in a world of sharp rocks and sharp teeth, these delicate footsies are prone to damage, forcing the sea cucumbers – like most echinoderms – to evolve remarkable means of healing and regeneration.
To understand what happens to the lost feet themselves, researchers collected a bunch of samples and kept a close watch over them in the ensuing days, analyzing their tissues and anatomical structures, and even using specially labeled amino acids and ammonia in the seawater to monitor the nutrients they absorbed.
Over the following week, the lopped-off locomotive tubes changed. Far from rotting away, a churning over of new and old cells helped the amputated limb heal, while immune cells exploded in numbers.
What was once a foot slowly transformed into a spherical blob of living muscle and connective tissue. Within a month, the site of the wound was indistinguishable from the rest of the sample. Pigmented cells migrated deeper inside, leaving a translucent “skin.” Two months later, the shrunken balls had returned to their original size. After three months, they had grown bigger than before.
A year rolled by. Then two. And still they lived, continuing their blind, lonely existence under a thick layer of sediment in the tanks. While none showed signs of becoming a whole new creature, the "feet" seemed quite content to soak up nutrients in the muck and live a life of their own.
“Natural seawater is just about the most microbially diverse, least clean approach we could take experimentally,” says Sipler. “Yet, that rich environment full of bacteria and all this organic matter was actually feeding them and allowing this tissue to heal and grow.”
Nature is full of examples of astonishing healing. Salamanders regrow limbs. Some jellyfish can return to immature states, making them virtually immortal. There are even planarians that can generate two new individuals from bodies that have been dissected in half. Among our own species, cancerous cells have astonishing abilities to persist, carrying on for generations under suitable conditions.
Finding examples of lost body parts that naturally defy death and decay in an environment as hostile as the ocean floor could change how we delineate the edges of biology.
“It’s like a lizard that loses its tail,” says Sipler. “We know some lizards can grow new tails; we’re talking about whether the tail can grow a new lizard.”
This research was published in Science Advances.
Source: Bigelow Laboratory for Ocean Sciences
Fact-checked by Darren Quick.
