Fig. 4. Metamorphic transformation of pharyngeal sense organs, as shown by MJ94/UAS-mCD8-GFP (green). Red indicates the Elav marker except in E,F, in which it indicates -caspase antibody. Stages are indicated in hours APF. (A-C) The pps maintains two sensilla throughout metamorphosis (arrows) each comprising three differentiated neurons, and becomes the dcso. (D-F) By contrast, the vps disintegrates in the early pupa and its neurons lose Elav immunoreactivity (D: arrows) or give rise to Elav-positive debris (D: arrowheads). Evidence for apoptosis is shown by staining with anti-caspase antibody (E). Neuronal identity of the apoptotic cells is indicated by mCD8 expression in the same optical section (E'). By contrast, anti-caspase antibody does not bind to the neurons of the dps (F,F'). (G-I) The dps with its clusters a and p1 is joined by two additional neurons (p2) from the dpo, forming a dps complex (dps c.). (J-O) Later on, the dps c. splits into two distinct sense organs, vcso and lso. The vcso includes p1 and p2, with six and two neurons, respectively (J-L). The p1 cluster comprises the distal and middle sensilla of the vcso, and the p2 cluster comprises the proximal sensillum. Five to six additional neurons deriving from dps and dpo remain outside the vcso (J-L: asterisks). At 24 hours APF, the neurons of the fishtrap bristles appear (L: arrowheads). In the lso, the a cluster (consisting of nine neurons) will form sensillum 7 (eight neurons; M: arrowheads) and an extra mononeuronal sensillum (M: small arrow). An additional nine neurons appear in the distal part of the lso (M,N: large arrows), four of which are associated with bineuronal sensilla 8 and 9 (M-O: asterisks). White dots indicate midline; distal is to the bottom except in F,F', in which distal is to the left. Scale bar, 20 µm.