A painted robot fish with a smiley face became an instant celebrity when placed in a tank containing living versions of itself.

Scientists found their creation attracted both male and female zebrafish which were drawn by movements of its mechanically operated tail.

The 15cm-long robot was spray painted with characteristic blue zebrafish stripes, and given a "smile".

robot fish

The robot was painted to look like a zebrafish

Researchers hope more advanced robot fish will in future contribute to conservation and the control of pest species.

The robot, built by US and Italian scientists, had a rounded shape to mimic the look of fertile females, which are popular with male and female zebrafish alike.

Placed in a fixed position in a 65 litre tank, its tail movements were controlled by the researchers who filmed the results.

Both individual fish and shoals were attracted to the artificial newcomer.

While the noise of the robot's motor tended to put the fish off, the beating tail drew them in.

The experiment is reported in the journal Bioinspiration and Biomimetics.

Lead scientist Dr Maurizio Porfiri, from the Polytechnic Institute of New York University, said: "These findings provide practical evidence that a species' preference for conspecifics may be used to inspire the design of robots which can actively engage their source of inspiration.

"New studies are currently under way in our lab investigating the interactions between fish and robotic fish when they are free to swim together under controlled and ecologically complex conditions."