Ultrastructural Study Of Type "B" Neurosecretory Cells In The Earthworm Nervous System

Abstract

Neurosecretory cell types Bi—B5 are widely distributed throughout the cerebral, subesophageal, nerve cord and peripheral ganglia of the oligochaete Aporrectodea caliginosa, Lumbricus terrestris, Eisenia foetida, Octolasion cyaneum, De-ndrobeona subrubicunda and Allolobophora longa. Cell types are distinguished by certain cytological and ultrastructural features. Nerve fibres of each cell type extend centrally and/or peripherally in each ganglion where release of neurotrans-mitters/neuromodulators take place by exocytosis. Elements of neuromuscular junctions, within the perineurium, are compared with the body wall and heart muscle junctions to detect the origin of neuromuscular fibres. Other ultrastructural elements were also investigated by using zinc iodide osmium tetroxide reagent.