Novel synaptic structures in the central nervous system of the locust Schlstocerca gregaria

Summary An electron-microscopical study of locust thoracic ganglia reveals that synapses in the neuropily are morphologically heterogeneous. In addition to the conventional dyadic type described frequently in the literature, there is a second type with a complex arrangement of presynaptic dense material and a non-dyadic postsynaptic configuration. Serial-section analysis of these synapses suggests that the presynaptic structures include irregular or curved bars, and small projections.Although the proportion of non-dyadic synapses in the neuropile as a whole is small, a substantial number have been found on the branches of an identified flight motor neurone, labelled intracellularly with metal ions in conjunction with silver intensification. Samples from the arborization of this neurone give some indications of the distribution of non-dyadic synapses on it.The results are discussed in the context of distribution of synapses on other identified locust neurones, and the functional morphology of synapses in other phyla.