GLIAL-CELLS IN INSECT GANGLIA

Glial cells associated with elements of central neuropils in several i nsect species were studied with conventional light and electron micros copical techniques, the Golgi procedure, and a combination of the latt er with electron microscopy. Different types of cells located in the l ayer of cells covering the neuropil were found to send complex arboriz ations into synaptic neuropils. These arborizations grow in clusters t hat seem to represent discrete compartments circumscribing groups of s ynaptic terminals. The thinnest glial processes are found deep in the neuropil and consist of compact membrane leaflets lacking cell organel les and with reduced amounts of cytoplasmic matrix. Some of these glia l processes also invest neuropil tracheoles in a manner reminiscent of the association between astrocyte end-feet and blood capillaries in t he central nervous system of mammals. Other glial cells reside complet ely in the neuropil, where they enwrap fiber bundles in a similar mann er to oligodendrocytes in the central nervous system of mammals. (C) 1 996 Wiley-Liss, Inc.