Fig. 1. Identification of peripheral dendritic arborization (da) neurons using the MARCM system. (A) A diagram of the Drosophila abdominal peripheral nervous system modified from Brewster and Bodmer, and Merritt and Whitington (Brewster and Bodmer, 1995; Merritt and Whitington, 1995). da neurons, red diamonds; external sensory neurons, yellow circles; other multidendritic neurons, green triangles; chordotonal organs, blue rectangles. The lateral oenocytes are shown as gray ovals. We have designated names for the dorsal cluster neurons on the basis of their typical ventral to dorsal cell body position. (B) Gal4 109(2)80-driven mCD8::GFP in third instar md neurons, oenocytes and chordotonal organs. An arrow indicates the position of the neuron labeled in C. (C; top) Components of the MARCM system used to characterize the normal morphologies of da neurons. (Bottom) A mitotic clone of ddaD. (Its location within a typical hemisegment is indicated by a white arrow in B.) (D) Computer tracings of the branching patterns of the four classes of neurons. Representative main branches and side branches from single neurons in each class are shown. These branches are not oriented according to larval axes. Dorsal is up and anterior to the left in panels A-C. Scale bars, 100 µm (B); 50 µm (D).