Fig. 2. CAN axon morphology in wild-type, vab-8 and unc-51 animals. (A) Schematic representation of a CAN cell body and its axons. The centrally positioned CAN cell body extends an axon anteriorly to the nerve ring and an axon posteriorly to the tail near the PHA/B sensory neurons. (B-F) Fluorescence photomicrographs of larvae carrying a Pceh-23::gfp transgene, which expresses GFP in the CANs, as well as sensory neurons in the head and the tail. The CAN cell bodies (large arrowheads) and their axons can be visualized using this transgene. An arrow indicates the position of an axon termination. (B) Wild-type third larval stage hermaphrodite. (C) vab-8(ev411) first larval stage hermaphrodite. (D) vab-8(ev411) fourth larval stage hermaphrodite. The asterisk indicates the position where the posterior axon had reversed and extended anteriorly. The penetrance of this misrouting defect is 29% for ev411. (E,F) The small arrowheads point to large varicosities that often flank the CAN cell bodies in unc-51 mutants. (E) Anterior half of an unc-51(e369) third larval stage hermaphrodite. (F) Posterior half of a different unc-51(e369) larva. The open arrowhead points to an out-of-focus CAN cell body. Scale bars: 20 µm.