Cut from the animal and left in seawater, the tissues absorbed nutrients and survived
A young scarlet sea cucumber, about 5 millimeters long, uses its tentacles to feed. While sea cucumbers can naturally shed and regenerate these tentacles, researchers have also found that detached tentacle tissues can remain alive independently after being separated from the organism.
Sara Jobson/Mercier Lab/MUN
Thing, the disembodied hand that loyally roams the fictional Addams Family in the popular television series, does not exist. Wednesday. But at least one species of sea cucumber appears to have evolved surprisingly closely.
Tissue detached from the appendages of a scarlet sea cucumber (Thanks to the factory) survived for over three years in running seawater without special nutrients or antibiotics, researchers report May 29 in Scientific advances. This discovery could force scientists to rethink what tissue life means.
“It’s an astonishing finding,” but not entirely surprising given the sea cucumber’s remarkable capabilities, says José García Arrarás, a regenerative biologist at the University of Puerto Rico in San Juan. Some species can be cut in half, with each half regenerating completely. “But [the work] raises fascinating questions,” says García Arrarás, who was not involved in the research. “What type of cells are these? How do they feed? Can these tissues survive the animal itself?
Sausage-shaped sea cucumbers are marine invertebrates that typically range in length from a few centimeters to more than 30 centimeters, depending on the species. They live on the seafloor, from shallow coastal waters to the depths of the ocean, and are close relatives of starfish.
Scientists who study sea cucumbers In the laboratory, they are generally kept in tanks filled with fresh seawater, explains marine ecologist Annie Mercier. During a routine transfer of a scarlet sea cucumber between tanks, one of Mercier’s colleagues noticed that the animal had left behind some podia, small tubular appendages it uses to move around, at the bottom of the tank. This is also something that happens often in nature. “We would have expected them to decompose and disappear fairly quickly, but several days later they were still there,” says Mercier, of Memorial University of Newfoundland in St. John’s, Canada.
Surprised, Mercier and his colleagues studied what would happen to other tissues cut with a scalpel, including tentacles and body wall. While the body wall tissues died within a few weeks, the tube feet and tentacles survived for more than three years.
Using a typical compound microscope, the researchers observed that the tissue underwent wound cleaning where it had been cut, removing old dead cells and dividing living cells. When the researchers added amino acids labeled with a traceable atomic tag to seawater, they could see that the tissues absorbed the nutrients. The tissues did not deteriorate even after being buried in a few centimeters of mud.
“We started calling it our ‘zombie project,’” Mercier says. “It’s a piece of tissue that doesn’t decompose. It continues to acquire nutrients, remodel itself, evolve and create all sorts of living things, but it’s not necessarily a living organism in the traditional sense.”
This work may offer new ways to study the changes that occur during aging, says García Arrarás. “They have some fabrics that are a week old and some that are three years old, from the same original fabric,” he says. However, a key next step should be to detail the characteristics of cells present in tissues. “You have to know exactly what you have” before you can understand what’s going on, he says.