RESUMEN
The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin and castrated, and reproducing mated Helisoma duryi have been examined using serial sectioning. The DB cells occur in two masses on the mid-dorsal side of the cerebral commissure, each of which has a cortical zone containing the cell bodies and a medulla where cell processes terminate. The cell bodies measure 10-15 µm in diameter, and are arranged in lobules of 6-12 cells. The complex cell processes are winding and terminate at various distances from their cell bodies in both reproducing and non-reproducing snails. Few 70-90-nm membrane-bound granules are found in the cell bodies and many are seen in the cell processes, which seem to penetrate the perineurium of the cerebral ganglia and make close contacts with neurosecretory cells. In reproducing snails the DB cells display a significantly larger amount of plasma membrane sproutings in the form of loops and circles compared to that in reproductively inactive virgin or castrated snails. Images of thin-sections and freeze-fracture replicas of these membranes suggest that they are gap junctions, which join the DB cells with each other. It is likely that gap junction-mediated cell to cell communication is involved in the activation of the DB cells for their role(s) in reproduction.
