Scientists who produced the first “living robots” say the life forms have found a way to reproduce.
The blob-like xenobots, which are less than a millimetre wide, were formed from the stem cells of the African clawed frog - xenopus laevis - from which they take their name.
They were first unveiled in 2020 after experiments showed they could move, work in groups and even heal themselves.
Now the US scientists who developed them say the xenobots have discovered an entirely new form of biological reproduction, different from any animal or plant known to science.
"I was astounded by it," said Michael Levin, a professor of biology and director of the Allen Discovery Centre at Tufts University, who was co-lead author of the new research.
"Frogs have a way of reproducing that they normally use but when you liberate (the cells) from the rest of the embryo and you give them a chance to figure out how to be in a new environment, not only do they figure out a new way to move, but they also figure out apparently a new way to reproduce."
"Most people think of robots as made of metals and ceramics but it's not so much what a robot is made from but what it does, which is act on its own on behalf of people," said Josh Bongard, a computer science professor and robotics expert at the University of Vermont and lead author of the study.
"In that way, it's a robot but it's also clearly an organism made from genetically unmodified frog cell."
Mr Bongard said the xenobots, which were initially sphere-shaped and made from around 3,000 cells, could replicate, but it happened rarely and only in specific circumstances.
The xenobots used "kinetic replication" - a process known to occur at the molecular level but has never been observed before at the scale of whole cells or organisms, Mr Bongard said.
With the help of artificial intelligence, the researchers then tested billions of body shapes to make the xenobots more effective at this type of replication.
The supercomputer came up with a C-shape that resembled Pac-Man, the 1980s video game. They found it was able to find tiny stem cells in a petri dish, gather hundreds of them inside its mouth, and a few days later the bundle of cells became new xenobots.
"The AI didn't program these machines in the way we usually think about writing code. It shaped and sculpted and came up with this Pac-Man shape," Mr Bongard said.
"The shape is, in essence, the program. The shape influences how the xenobots behave to amplify this incredibly surprising process."
The xenobots are very early technology and don't yet have any practical applications. However, this combination of molecular biology and artificial intelligence could potentially be used in a host of tasks in the body and the environment, according to the researchers. This may include things like collecting microplastics in the oceans, inspecting root systems and regenerative medicine.
The study was published in the peer-reviewed scientific journal PNAS on Monday.