A manipulator is configured with three or more substantially concentric, elongate members configured such that relative rotation and translation of the elongate members adjusts both the spatial position and orientation of the distal end of the manipulator and the spatial positioning of the manipulator along its length. In one arrangement, the elongate members are pre-curved such that the distal end portions of the elongate members have generally arcuate shapes in a resting state. When the three elongate members are combined in a substantially concentric manner, the overall shape of the manipulator is a composite of the individual elongate member shapes. Varying the relative translation and rotational orientation of the component elongate members achieves a family of resulting manipulator shapes as well as a desired spatial position and orientation of the distal end portion of the manipulator.