A preliminary account of brain growth in postlarval Nereis virens (Polychaeta: Annelida): a [3H]thymidine study

Abstract

Labelling of the supraoesophageal ganglion of postlarval Nereis virens with [3H]thymidine indicates that cell division is most active in very small worms, less than 0.1 g in weight. In such animals a few, small, labelled neurons were found, but only after 13 h of exposure to isotope. After shorter exposures, very small, undifferentiated labelled cells were seen in most of the ganglionic areas of the brain, although the various ganglionic nuclei differ in the time of first appearance of their characteristic neurons. In older animals gliagenesis continues at a reduced rate and neuron production becomes extremely slow.