Effects of Neuroendocrine Centers on Germ and Germline Cells in Dendrobaena atheca Cernosvitov (Annelida: Lumbricidae)

Abstract

The aim of the present comprehensive experimental study was to reveal the effects of the removal and the regeneration of the main neuroendocrine centers in the oogonia, oocytes and trophocytes in Dendrobaena atheca. Various types of serial sections of ovaries and cephalic regions were obtained. Four histological staining techniques were employed. In controlled preparations, the neurosecretory activities of A-cells and C-cells showed correlation with cellular activities of oogonia, oocytes and trophocytes. In experimental preparations, removal of A-cells caused abnormalities in oocytes and trophocytes. The regeneration of A-cells restored vitellogenesis and repaired abnormalities. In both preparations, C-cells remained aldehyde-fuchsin (AF)-positive. B-cells and U-cells remained AF-negative. The oogonia showed continuous mitotic divisions. Regenerated A-cells appeared in week 3, increased in number, but could not stop the abnormalities, as hormones were not transported due to the lack or scarcity of blood capillaries. Therefore, abnormalities increased extremely. Then, they stopped, decreased, and were repaired due to hormonal transport via fully reconstructed blood capillary plexuses. The main conclusions are: (1) oocytes and trophocytes are controlled by A-cells, since they exhibited prominent changes during the removal and regeneration of A-cells; (2) oogonia are controlled by C-cells, as they showed correlation of activities with C-cells and were not affected by the removal and regeneration of A-cells; (3) B-cells and U-cells remained inactive; hence, they have no role in oogonia divisions and vitellogenesis; and (4) delayed hormonal effects of regenerated A-cells were due to the lack or scarcity of blood capillaries. Therefore, fully reconstructed blood capillary beds in the A-cells area are indispensable for hormonal diffusion, transport and effectivity.