Jellyfish-like 'Medusoid' created

It resembles an other-worldly alien from a sci-fi movie and has a name to match. But real-life scientists created the multi-limbed "Medusoid" which swims with the help of pulsating rat heart cells.

The artificial creature, measuring several centimetres across, is made of transparent elastic silicone. It propels itself through water with pumping movements when stimulated with electricity, but has no brain - yet.

Experts hope to evolve self-contained future versions that are able to respond to their environment, and even seek energy or food.

Tissue engineers in the US based the design of the Medusoid on the jellyfish, believed to be the most primitive multi-organed animal.

Jellyfish swim using rhythmic movements similar to that of the human heart. Scientists achieved the same result by seeding rat heart cells into an eight-fingered silicone polymer membrane.

Professor John Dabiri, a member of the team from the California Institute of Technology (Caltech), said: "I was surprised that with relatively few components - a silicone base and cells that we arranged - we were able to reproduce some pretty complex swimming and feeding behaviours that you see in biological jellyfish. I'm pleasantly surprised at how close we are getting to matching the natural biological performance, but also that we're seeing ways in which we can probably improve on that natural performance. The process of evolution missed a lot of good solutions."

Writing in the journal Nature Biotechnology, the scientists explained how they reverse-engineered the jellyfish by mapping its muscle architecture. This was used to create a pattern of protein molecules, printed on to silicone, that guided the growth and organisation of the rat tissue.

Even when removed from the heart, individual heart cells will contract in response to an electric current.

After releasing their creation into a fluid-filled tank, the scientists were able to "shock" it into moving with five-volt electric pulses. The Medusoid swam with synchronised contractions mimicking those of a real jellyfish.

Similar techniques could in future have therapeutic applications, such as "biological" pacemakers or bio-engineered organs, say the scientists.