Fine structure of cardiac ganglion trunk in prawn, Penaeus japonicus bates

The cardiac ganglion trunk of prawn, Peneaus japonicus Bates, is on the middle line of ventral wall of the cardiac tube and consists of nine ganglion cells, many nerve fibers and neuropils. These neuronal elements are insulated by supporting cells and connective tissue fibers. The peripheral area of the perikaryal cytoplasm of the ganglion cell is separated into many compartments by deep invaginations of the cell membrane. Each compartment is packed with a tight network of the agranular endoplasmic reticulum. Among nerve fiber bundles are many small areas of neuropil. Most of the synapses in the ganglion trunk are observed in the neuropil, but there are a few nerve terminals which form synapses with the somata of ganglion cells.