Fig. 5. Changes in distribution of traction stress generated by a mlcE^– Dictyostelium cell during a `slow recoil' retraction. (A-H) A time series of traction vector maps obtained from a mlcE^– cell moving in the general direction indicated (arrow), during one cycle of movement. An asymmetrical distribution of high traction stress develops very slowly at the rear and along the lateral cell edges (A,D) prior to retraction (R in E, arrow). During the slow recoil retraction, traction stress decreases gradually together with a progressive loss in front-rear asymmetry (E-H), while protrusion (P in E) is occurring at the cell front, where traction stresses are low. Bar, 3 µm. (I) Plots of the 90th percentile traction stress (red), instantaneous speed (green), cell area (blue) and shape factor (yellow) corresponding to panels A-H. The slow recoil retraction (R) occurs between 28–52 seconds, as indicated by the vertical dotted lines.