RIS is an interneuron with a single cell body situated on the right-hand side of the ventral ganglion behind the excretory duct. A single, fairly large process leaves the cell body and runs anteriorly on the dorsal surface of the nerve cord. A short branch dips down into the body of the nerve cord and makes a very characteristic gap junction to AVJ (*c). The main process runs in the middle of the dorsal surface of the nerve cord until the nerve ring is reached. It then runs round the nerve ring in an anticlockwise direction, running near the anterior face and outside surface. The right- and left-hand regions of the process appear symmetrical, although they are running in opposite directions with respect to the cell body. The main synaptic outputs are to AVE (a), RIM (b), RMD (d), RIB (c), CEP (a) and AVK, usually in various dyadic and triadic combinations. There is not much synaptic input; what there is comes mainly from SDQ and PVC. Gap junctions are made to AVJ (*c), SMD, RIM and AIB. Magnifications : (a) 25500 , (b-d) 17 000.
Web adaptation, Thomas Boulin, for Wormatlas, 2001, 2002