A robot that looks and moves like a salamander and is controlled by a system that imitates the amphibian's spinal cord, enabling the machine to alternate between swimming and walking, is seen in this undated handout photo taken in Switzerland. (Xinhua/Reuters Photo) Photo Gallery>>>

    WASHINGTON, March 9 (Xinhua) -- Scientists have designed a salamander robot that can switch between swimming and walking by increasing the strength of the electrical signal through an amphibian-like central nervous system, according to new research in the 9 March issue of Science.

    By designing a machine that can walk and swim without redesigning its joints or central nervous system, the researchers believe the robotic amphibian can provide answers to how the first vertebrates transitioned from sea to land.

    The 85-cm-long robot, built by Auke Jan Ijspeert and colleagues in Switzerland and France, has a spinal cord model on board that receives simple control signals. Sent wirelessly from a PC, the signals modulate the speed, direction, and type of gait similarly to the signals coming from the neural centers in vertebrate animals.

    With its six spinal hinges, four rotational limb joints, and 10motors, the robot is able to mimic the S-shaped body undulation pattern that many amphibians use to drive themselves in terrestrial and aquatic environments.

    The researchers discovered that when the robot is stimulated with low levels of electricity, the robot adopts a walking gait, while higher levels cause the robot to switch to faster swimming motions.

    "The salamander, an amphibian, is regarded as among the... first terrestrial vertebrates and represents a key animal from which the evolutionary changes from aquatic to terrestrial locomotion can be inferred," the authors write.

    In addition to answering key questions about early evolution, the authors point out that their research is evidence of how robots can be used "as tools to test hypotheses concerning biological systems."