Dynamics of blebs and pseudopods. (A) Space-time plots comparing F-actin dynamics in a pseudopod and a bleb. Pseudopods are marked by a continuous, steady advance of F-actin at the leading edge, in contrast to the discontinuous advance in blebs. (B and C) Blebs are distinguished from pseudopods by their greater maximum speed of expansion, loss of F-actin at the membrane during expansion, and lower displacement achieved over their lifetime. For C, a set of 12 Ax2 cells expressing ABD-GFP and starved for 5–6 h was observed by spinning-disc confocal microscopy at 4.5 frames per second and analyzed by modified QuimP10 software (37 blebs; 88 pseudopods); loss of F-actin (B) was measured in manually identified projections from these same cells (12 blebs; 22 pseudopods). Each data-point represents a single bleb or pseudopod.