MUTATIONS THAT AFFECT THE LENGTH, FASCICULATION, OR VENTRAL ORIENTATION OF SPECIFIC SENSORY AXONS IN THE DROSOPHILA EMBRYO

In wild-type Drosophila embryos, five lateral chordotonal (Ich) axons in each abdominal hemisegment originate from a midlaterally positioned cluster of neurons and grow, fasciculate, and orient ventrally as the y connect with targets in the CNS. We have identified 22 recessive let hal mutations in 12 complementation groups, 8 of which are novel, that differentially affect lch axon growth, fasciculation, or ventral orie ntation. Mutations in 3 loci result in shorter, but fasciculated and v entrally directed axon bundles. Mutations in 4 complementation groups cause Ich axon defasciculation. Mutations in 7 complementation groups cause some Ich axon bundles to grow dorsally along a trajectory 180 de grees from normal.