Blebs formed by Dictyostelium cells moving under buffer. (A) Blebs (black dots) formed at the leading edge of a cell expressing an F-actin reporter. Blebs are small and expand in less than one second, leaving behind an F-actin scar (white arrows), but rapidly regain an F-actin cortex (see Video 1). (B) The cell leading a small stream moving in bleb mode (see Video 3). (C) Transformation of a bleb (arrowed) into a pseudopod by continued actin polymerization. (D) A composite bleb and pseudopod (“blebbopodium”). (E) Detail of the transformation of a bleb into a pseudopod by continued actin polymerization (see Video 2). Ax2 cells expressing the F-actin reporter ABD120-GFP were starved for 5.5 h, or 6.5 h for B. Confocal fluorescence and DIC images obtained at 1 frame per second; Bars: (A, B, and D) 10 µm; (E) 1 µm.