SIA is a set of four interneurons, which send processes posteriorly down the sub-lateral cords. All four cell bodies are in the ventral ganglion. The SIAD pair sends processes that enter and run round the nerve ring, leaving it on the contralateral side along with the four other processes that make up the sub-lateral cords (e). The SIAV pair sends processes into the ring, which loop back on the ipsilateral side, reentering the neuropile of the ventral ganglion; these processes then leave the ventral cord at the amphidial commissures and enter the sub-lateral cords along with four other processes (f). SIA is unusual in that it appears to have no synaptic outputs except, perhaps, via gap junctions to RIB (a). Synaptic input is sparse and comes mainly from CEP (b) and RIA (c). SIA is similar in some respects to SIB; the two sets of processes run together in the nerve ring near the centre of the neuropile (d). Magnifications: (a-d) x 12750.
Web adaptation, Thomas Boulin, for Wormatlas, 2001, 2002