Bioengineers have taken apart a rat and built a jellyfish.

The synthetic animal - called a medusoid - was put together with silicone and muscle cells from the heart of a rat.

It looks a bit like a flower with eight petals, and 'swims' when an electric current is passed through it.

“Morphologically, we’ve built a jellyfish. Functionally, we’ve built a jellyfish. Genetically, this thing is a rat,” said Kit Parker, a biophysicist at Harvard University in Cambridge, Massachusetts.

The research is published in Nature Biotechnology.

The animal was created as part of ongoing research into creating artificial human heart tissue.

Parker said he had the idea when visiting an aquarium in Boston.

"I saw the jellyfish display and it hit me like a thunderbolt," he said. "I thought: I know I can build that."

He recruited another bioengineer, John Dabiri, sand said his excitement proved infectious: "He didn’t know who I was, but I was pretty excited and waving my arms, and I think he was afraid to say no," Parker said.

The team now plans to build a similar hybrid animal using cells from a human heart. They say it can help test drugs, and have filed a patent for their design.

"You’ve got a heart drug?” says Parker. “You let me put it on my jellyfish, and I’ll tell you if it can improve the pumping."

Nature said they also have other animals ready to go.

"We’ve got a whole tank of stuff in there, and an octopus on order," Parker said.