Interganglionic variation in cell body location of snail neurones does not affect synaptic connections or central axonal projections

Abstract

RECENT accounts of invertebrate nervous systems have emphasised constancy in the occurrence and electrical properties of large identifiable neurones^1–5. That constancy, however, has limits, and some giant neurones show variation in peripheral axonal projections¹ and dendritic morphology^6–8. Smaller neurones increase in number during post-embryonic growth in several groups of invertebrates⁹. During electrophysiological mapping experiments on the brain of the pulmonate pond snail, Lymnaea stagnalis (L.), we have found two giant neurones whose positions varied considerably between ganglia, although the variation in cell body position was not associated with any variations in the synaptic connections of the neurones with each other or in identifiable synaptic inputs from other neurones, or with variations in the final projection areas of the principal axons within the brain. Some variation in the detail of axon branching was found to be correlated with cell body location for one peripheral projection.