Location of interganglionic neurons in the stomatogastric system of the spiny lobster.

The stomatogastric ganglion produces distinct and complex patterned output driving the mastication and filtration of food. It does so with a small number of neurons whose properties and interconnections have been extensively examined. The motor patterns are subject to modulation and integration by neurons of other ganglia. This paper reports a search for interneurons of the four interconnecting ganglia of this system, using cobalt chloride backfilling techniques. It was determined that only a small number of neurons may interconnect these ganglia: (1) In the stomatogastric ganglion there are two to three small neurons and six large neurons with neurites projecting anteriorly towards the other ganglia. (2) In the two commissural ganglia there are one to three small neurons whose neurites project to the primary input nerve of the stomatogastric ganglion. (3) In the oesophageal ganglion there are three small neurons whose location would allow them to play a co-ordinating role in the output of all four ganglia.