12:43pm UK, Thursday March 02, 2006

Remote-controlled sharks may be used by scientists to patrol the waters off the United States.

The "stealth sharks" will be guided by electrodes in the brain, it has been revealed by the Pentagon.

180 Great white shark generic swimming

An underwater spy?

Scientists want to exploit the natural ability of sharks to glide swiftly and silently through water totrack movements by enemy vessels and smugglers.

The research builds on developments in brain implant technology which have already seen scientists controlling the movements of fish, rats and monkeys.

Scientists from the US Defence Advanced Research Projects Agency plan to implant devices into blue sharks and release them into the ocean off the coast of Florida.

Sonar beamed from naval acoustic signalling towers would be used to communicate with the sharks.

A limit will be set on each shark's time on the job to protect it from exhaustion, New Scientist magazine reported.

"Despite this limitation, though, remote controlled sharks do have advantages that robotic underwater surveillance vehicles just cannot match. They are silent and they power themselves," it said.

Other animals have been used in similar ways.

The New York Police Department is considering recruiting rats to its disaster response team to look for hidden bombs or people trapped under rubble.