Michael Levin led a team that examined how living in space affected the growth and regeneration of planarian flatworms and how their bodies adjust upon their return to Earth. Levin and Junji Morokuma are quoted.
Researchers sent flatworms aboard the International Space Station for five weeks to study how an absence of normal gravity can affect behavior and anatomy – in particular, their ability to regenerate missing parts.
Flatworms were either left whole or amputated, and most surprisingly, one of the amputated fragments regenerated into a double-headed worm.
When the researchers amputated both heads, they also discovered the headless middle fragment regenerated into another double-headed worm.