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Fig. 9 Lateral view of whole-mounted zygotes showing the movement of inclusions during pulsations and the effect of actin poisons. A: Movement of 5 inclusions during a high-frequency pulsation in a stage 1b zygote. The time-lapse for each inclusion was taken independently at 10-sec intervals, marking the successive position of the inclusion with red dots and the path with straight lines linking the dots. Numbers indicate the initial position of the inclusion. The movement pattern of the inclusions was saved in the last image of the stack. Inverted contrast live (B-D) and acid-fixed (E, F) whole-mounted zygotes showing that blockade of pulsations after drug incubation was accompanied by disorganization of the endoplasmic lacunae. B: Incubation in Cytochalasin B for 45 min. C: Incubation in Latrunculin B for 2 hr. D: Control (ctr) incubated for 45 min in aquarium water with DMSO, showing that in this case the actin ring contracted and the axial streamers formed (as). E: Latrunculin B-treated zygote showing disruption and enlargement of the endoplasmic lacunae after 80-min incubation in the drug. F: Control zygote incubated for the same amount of time in 2% DMSO. Notice the absence of endoplasmic lacunae and the division of the blastodisc. G,H: Low- and high-magnification images of fragmented actin (fa) in endoplasmic lacunae of a zygote incubated in Cytochalasin B for 80 min. I: Actin network (act) in a lacuna of a control zygote incubated in 2% DMSO for the same amount of time. J,K: Low- and high-magnification images of fragmented actin in the ectoplasm (ec) of a zygote incubated in Latranculin B for 1 h. L: Actin network of a control zygote incubated for the same amount of time in 2% DMSO. Development at 25°C. bd, blastodisc. Scale bars = 16 μm (A), 60 μm (B-F), 45 μm (G ), 25 μm (H), 7 μm (I), 12 μm (J), 20 μm (K), 7 μm (L).