Figure 3.

AF11 immunoreactivity in AVK neurons and their processes. (a–d) Whole mount preparations; (e) cross-section of plastic-embedded VC. (a) Stained AVK neurons each send a process anteriorly toward the midline, turn ipsilaterally into the NR, proceed all the way around the NR, and then proceed posteriorly down the contralateral side of the VC. The AVK processes usually extend fine, short projections within the NR as well as in the area where they enter and exit the NR into the VC (arrowheads). Inset: higher magnification of another preparation where the AVK processes enter and exit the NR; arrowheads indicate fine extensions. (b) AF11-immunoreactivity in ALA neuron cell body in the dorsal ganglion. ALA sends two processes into the NR with one traveling down the left lateral line (LLL) (faint line) and the other traveling down the right lateral line (not shown). Note the stained AVKL neuron in the lower right. The NR is intact in this preparation, but the processes extending from ALA to the lateral lines were broken during dissection. (c) Stained AVK processes traveling separately down the VC. Note varicosities. (d) Stained AVK process ending in an apparent terminus in the region of the gonopore. (e) In transverse section, the stained AVK axons (arrowheads) travel at different levels in the VC. Their size and position identify them as being in the class of small VC interneurons. Muscle (m), hypodermis (h). The hypodermis that underlies the cuticle is near the bottom edge of this panel; near the top edge is the region where muscle arms divide into fine interdigitating fingers that receive synapses from motor neurons in the VC. Nerve ring (NR), ventral nerve cord (VC), AVK left (AVKL), AVK right (AVKR).