Fig. 2.

Analysis of the movement behavior of a Dictyostelium cell migrating up a gradient of the chemoattractant cAMP emitted from a micropipette (see SI Appendix A). The arrows indicate the intensity and direction of the vector data. The color contours indicate their intensity according to the color bars. The black arrow indicates the direction of motion of the cell. (Top) Instantaneous displacements in micrometers. (Middle and Bottom) Instantaneous stresses in pascals; the diagrams on the right show the cell's principal axes and the front (F_f) and back (F_b) pole forces. (Middle) h − h₀ = 0.4 μm; F_f = 156 pN, F_b = 162 pN. (Bottom), h = h₀; F_f = 143 pN, F_b = 149 pN.