Space travel, spontaneous fission, a worm that grows two heads—given these otherworldly elements, it’s no wonder that a recent paper published in Regeneration by researchers at Tufts’ Allen Discovery Center is generating so much buzz.

The experiment went like this: send seventy-eight flatworms (some with amputated body parts, others intact) to live aboard the International Space Station for five weeks, then compare them to worms with the same amputations that stayed behind on earth. The goal was to gather clues on how space travel affects the microbiology, morphology, and behavior of flatworms, and impacts their ability to regenerate.

Flatworms, which can grow back lost body parts, are ideal subjects when it comes to understanding how living systems repair themselves. This concept is central to regenerative medicine—the idea that we can harness the body’s own repair mechanisms to heal organs and tissues damaged by disease, injury, and congenital conditions.

The regenerative processes that happen naturally—in both humans and flatworms—are thought to be impacted by physical forces, including the earth’s gravity, and its natural electric and magnetic fields. It’s possible that someday those physical forces could be manipulated to encourage regeneration. “By learning about how regeneration works in different environments, it’s likely that we will uncover novel ways to control what cells do,” said Michael Levin, director of the Allen Discovery Center at Tufts. And that, he said, could lead to “new therapeutic interventions that can be applied here or in space environments.”


The Tufts researchers sent the flatworms up to the space station in January 2015. When the worms returned, they showed a marked difference from those that had stayed behind. The greatest surprise came from a worm that had had its head and tail amputated by the researchers prior to launch. Upon the worm’s return to earth, its head had regenerated—but it had also grown a second head where its tail should have been. When the team amputated each of those heads, both grew back a second time—evidence that the change had stuck. Though the spontaneous growth of two heads can happen among earthbound worms, it is extremely rare. In eighteen years of maintaining flatworm colonies, the Tufts team had witnessed it only in worms treated in ways that perturbed their natural bioelectric or biochemical pathways.

“To see such a drastic anatomical change made it clear to us that the normal processes of regeneration were profoundly affected by the experience of space travel,” Levin said.

There were other changes to the space worms, too. When placed in clean water, they went into shock, suggesting an altered biological state. And nearly two years later, they continued to exhibit a modified microbiome, plus behavior changes, including a greater tendency to move toward light.

In addition to providing insight into regeneration in the absence of earth’s gravity and magnetic fields, the experiment showed that space can influence behavior and microflora—a key finding as humans push the boundaries of space travel.

Exciting results all told, especially considering there was a risk the animals wouldn’t make it at all. When the worms landed, “we didn’t even know if [they] had survived,” Levin said.