Fig. 7. N-derived progeny are required for the normal intraganglionic migration of the O-derived P_D neuron. Each panel shows one (D) or two (A-C) segmental ganglia from germinal plates in which both the left and right O lineages were labeled with lineage tracer (green). P_D (arrows) and oz2/oz3 (arrowheads) are indicated when they can be distinguished from other O-derived cells. In A and B, the N lineage was labeled with lineage tracer (red) on the left side and is absent on the right side, owing to teloblast ablation. (A) By 80-85 hours clonal age, P_D and oz2/oz3 were readily distinguished on the control (left) side. In the absence of the N lineage (right side), oz2/oz3 migrated to their normal peripheral positions, but P_D apparently remained within a central cluster of O-derived cells. (B) Earlier in development (50-55 hours clonal age), P_D, oz2 and oz3 assumed their normal positions, independent of the N lineage (compare positions of O lineage cells on left and right sides). P_D has not yet separated from the central cluster of O-derived cells (compare with A). (C,D) ACT immunostaining (red) of axon projections reveals that PP nerve fibers still connect P_D and oz2/oz3 in N-depleted hemiganglia (right side). As P_D has failed to migrate normally, the PP nerve now branches from a central position in N-depleted hemiganglia (compare right side to left side). Ganglia are between 80-85 hours clonal age. Anterior is upwards. Scale bars: 25 µm in all panels.