Fig. 5. Analysis of NSM morphology in unc-86 mutants. Serotonergic neurons in wild-type (A) and unc-86 mutants (B-E) were visualized by anti-serotonin antibody staining. In wild-type animals (A), NSM has two posterior-directed processes. The position and the gross axon morphology of NSM in unc-86-null mutants are indistinguishable from wild-type, but neurite outgrowth defects were observed. Representative examples of outgrowth defects of NSM are shown. The arrows indicate neurite outgrowth defects in the corresponding neurons. In most cases, an extra neurite extended anteriorly to various lengths (B), one of the posteriorly directed axon was either premature terminated (C) or missing (D). In some cases, NSM had one anterior- and one posterior-directed process (E). Similar defects were observed in unc-86(n846) and unc-86(e1416), and there was no obvious difference in the frequency of the defects observed in the larvae and adults.