Embryonic development of axon pathways in the Drosophila CNS. II. Behavior of pioneer growth cones

We have identified the neurons that pioneer the major CNS axon tracts in the Drosophila embryo and determined their trajectory and fasciculation choices using serial section electron microscopy. Although Drosophila pioneer neurons make choices similar to those of their grasshopper homologs, there are interesting differences that reflect the much smaller nervous system size and the much faster rate of development characteristic of Drosophila. …