NeuroFIG 8: Location of body commissures in the head, neck, and tail regions.

A. The anteriormost body commissures belong to DB1 and VD1 neurons, which run on the right side. The DB1 commissure travels from the ventral side to the DC around the posterior of the pharyngeal procorpus (out of view to extreme left of panel). The VD1 commissure is located at the level of the terminal bulb of the pharynx. Slightly posterior to the VD1 commissure, processes of DD1, VD2, DB2, and DA1 travel to the DC. At the level of VD2 neuron soma, the RVG becomes continuous with the region containing the VNC motor neurons.
B&C. DB1 processes and commissure. Left lateral (B) and right lateral (C) views. DB1 has both anteriorly and posteriorly directed processes within the VNC. The posterior process ends in the anterior body, and the anterior process travels to the level of pharyngeal pro-corpus, where it makes a dorsal turn and reaches the DC via a right-sided commissure. The DC process then travels posteriorly past the terminal bulb and terminates at a variable distance within the anterior body (S. Fields, pers. comm.). Epifluorescent images of transgenic animals expressing yellow fluorescent protein (YFP) driven by a 7-kb hum-2A promoter in the DB1 neuron, some other neurons, and the amphid socket (AmSo) cells. (Image source: S. Fields.)
D. Schematic rendition of the nerve cords and commissures in the tail tip (also see NeuroFIG 18), left lateral view. The posteriormost body commissure belongs to AS11 and extends on the right side. The DA8 process travels into the DC. The PDB motor neuron process travels to the posterior through the right-side lumbar commissure, extends along the right lumbar ganglion, and reaches near the tail tip before making a dorsal turn and extending into the DC. Posterior processes from PLNs, ALNs, PHCs, and PVR (on the right side) extend straight into the tail tip. The AVG neuron process traverses the body in the VNC, reaches the left lumbar ganglion via the left lumbar commissure, and extends into the tail tip.

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