This observation leads me to the following question: Which neuron in C. elegans has the largest span, and why is it this large?
I am a member of OpenWorm.org, an open-source project that aims to simulate a C. elegans cell-by-cell. I didn't know the answer to this myself off the top of my head, but I have access to a number of folks who have been working hard on C. elegans anatomy for the last couple of years so I went ahead and asked them this question on our discuss mailing list. Thanks to Chris Grove and Tim Busbice for providing the answer that I am reporting below:
Also I would advise checking out the OpenWorm Browser - a web-based 3D viewer that you can use to explore the C. elegans anatomy cell-by-cell (the 3D model was developed by Chris Grove, see VirtualWorm for details). For instance you can easily search for those "longest" neurons mentioned above! Screenshot of one of them selected (AVDL) below:
Hope this helped!