The extremely asymmetric divisions of oocyte meiosis – by which oocytes become eggs – follow the central rule of animal cytokinesis: the cleavage furrow bisects the spindle.  It’s just that in oocyte meiosis, the spindle is small and directly associated with the plasma membrane.  The tiny polar bodies that result are dead-end cells containing throwaway copies of the maternal genome, but accuracy is at least as important as in normal cell division because partitioning errors would affect the egg and the embryo that develops from it.

This starfish oocyte expresses a probe for active Rho.  Immediately after the metaphase/anaphase transition, the entire oocyte surface experiences a short-lived wave of Rho activation, which heightens and “breaks” around the meiotic spindle, culminating in a bright zone of active Rho equivalent to the Rho zone in mitotic cytokinesis.  Rho activity in turn prompts actin assembly and myosin recruitment to mediate cell surface contractility, which is what pinches off the polar body.  In most oocytes Rho activation proceeds from vegetal pole to animal (where, by definition, the meiotic spindle is located); in this particular case, the wave travels too rapidly to be obviously directional unless one steps through the movie frame by frame (see the third movie below for a more obvious vegetal-to-animal wave).