Age-related histological changes in neurosecretory cells in the supraoesophageal ganglion of Nereis virens (Annelida, Polychaeta)

Abstract

The supraoesophageal ganglion of Nereis virens has been surveyed by light microscopy to determine the locations of probable neurosecretory cells. Neurons reacting with paraldehyde fuchsin are found scattered throughout the brain, but the majority are accumulated posteriorly in nucleus 20. This nucleus was examined in some detail, and the histology of four cell types is described. Two types (p and r) are strongly paraldehyde-fuchsin-positive, and may be secretory. On the basis of other staining characteristics, and uptake of labelled cystine, it is concluded that p cells are rich in cystine and (or) cysteine. A comparison of juvenile and adult brains revealed that the same cell types exist at both developmental stages, but that p and r cells increase in number and staining intensity with age. These findings are not consistent with the notion that these particular cells are the source of a "juvenile hormone' ' which has been reported to exist in nereids. Rather it is suggested that the described cells are producers of a maturation and (or) spawning hormone.