E. Basmer et H. Greven, ON THE ULTRASTRUCTURE OF THE CEREBRAL GAN GLION OF ENCHYTRAEUS-BUCHHOLZI (OLIGOCHAETA), Zoologischer Anzeiger, 231(5-6), 1993, pp. 219-238
The outermost layer of the cerebral ganglion of Enchytraeus buchholzi
consists of extensions of glial cells (type I) covered by a discontino
us muscle layer and cells of the peritoneal epithelium. The amount and
arrangement of glial cells, neurons and neuropile differ in the vario
us regions of the ganglion. Most pericarya of neurons are localized in
the caudal region surrounded by projections of glial cells. The neuro
pile is concentrated mainly in the middle portion of the ganglion. A s
ingle large cell (Q-cell) situated on each side of the brain shows a b
right fluorescence when treated with dibromobimane indicating the pres
ence of sulfur containing neuropeptides (neurosecretion). Q-cells are
characterized by numerous membrane-bound ''neurosecretory granules'' a
nd a well developed rough endoplasmatic reticulum. However, the cytopl
asm of the other neurons contains numerous more or less electron dense
granules of similar shape. In the axons of the neuropile two types of
synaptic vesicles (electron lucent, dense core vesicles) as well as '
'neurosecretory'' granules occur. Two types of glial cells can be dist
inguished: 1) cells with large pericarya and electron lucent cytoplasm
present only in few numbers (type I). Their projections cover the neu
rons and extend in the neuropile, where they possess glial filaments;
2) small more electron dense cells (type II) close to the neuropile ex
tending projections between the axons. Both contain typical glia grana
. In the anterior portion of the brain four to five receptor cells are
found having microvilli and numerous cilia, which show a 8 x 2 + 2 mi
crotubule-pattern.