RP2 disappearance occurs by programmed cell death. (A) Images showing ventral ganglia removed from animals at 14, 16 and 18 h-APF. At 14 h-APF, nearly the full complement (2 per neuromere; Table 1) of abdominal RP2s and aCCs were identifiable by location and GFP labeling. By 16 h-APF, many RP2s were missing or were rounded and condensed. By 18 h-APF, only the RP2s in neuromere A1 remained. In contrast, aCCs persisted throughout this period. Asterisk in (A3) marks an example of an unidentified GFP-labeled neuron. (B, C) GFP labeling (green) and TUNEL labeling (indicating DNA fragmentation; red) in mid-abdominal neuromeres. (B) At 8 h-APF, many TUNEL-positive nuclei were present but no RP2s or aCCs were TUNEL-positive. (C1-C3) Images from three different animals at 15 h-APF. TUNEL-positive RP2s are marked by dashed arrows. Scale bars: 20 μm.