Glial cells in the developing and adult olfactory lobe of the moth Manduca sexta

Abstract

The antennal lobe of the moth contains several classes of glial cells that are likely to play functional roles in both the developing and mature lobe. In this study, confocal and electron microscopy were used to examine in detail the morphology of two classes of glial cells, those associated with olfactory receptor axons as they course to their targets in the lobe and those that form borders around the synaptic neuropil of the olfactory glomeruli. The former, the nerve-layer glia, have long processes with multiple expansions that enwrap axon fascicles; the latter, the neuropil glia, constitute two subgroups: complex glia with large cell bodies and branching, vellate arbors; and simple glia, with multiple, mostly unbranched processes with many lamellate expansions along their lengths. The processes of complex glia appear to be closely associated with axon fascicles as they enter the glomeruli, while those of the simple glia surround the glomeruli as part of a multi-lamellar glial envelope, their processes rarely invading the synaptic neuropil of the body of the glomerulus. The full morphological development of antennal-lobe glial cells requires more than two-thirds of metamorphic development. During this period, cells that began as cuboidal or spindle-shaped cells that were extensively dye-coupled to one another gradually assume their adult form and, at least under nonstimulated conditions, greatly reduce their coupling. These changes are only weakly dependent on the presence of olfactory receptor axons. Glial processes are somewhat shorter and less branched in the absence of these axons, but basic structure and degree of dye-coupling are unchanged.

Standard three-dimensional glomeruli of the Manduca sexta antennal lobe: a tool to study both developmental and adult neuronal plasticity

“…Moreover, glial cells, which significantly contribute to glomerulus formation during phase 2 of pupal AL development, presumably do not participate in glomerulus maturation and growth during later stages (Baumann et al 1996;Oland et al 1999; for a review, see Tolbert et al 2004). This leaves anatomical changes in the neuronal components of the AL during phase 3 and in the adult as the basis for volume changes in the glomeruli.…”

Organization and Postembryonic Development of Glial Cells in the Adult Central Brain ofDrosophila

“…In the adult brain or ventral nerve cord of other insects, two types of glial cells associated with neuropil have been identified; type II and type III glia or interface and neuropilar glia in Musca (Sohal et al, 1972;Strausfeld, 1976), interface and neuropil glia in Acheta (Meyer et al, 1987) and neuropil cover type and neuropil glia or simple and complex neuropil glia in Manduca (Cantera, 1993;Oland et al, 1999). One type is localized cortex/ neuropil interface or borders among neuropils and ensheaths neuropil, and another type extends glial processes inside the neuropils, like the ensheathing and astrocyte-like glia of adult Drosophila brain, respectively.…”

Delayed axonal pruning in the ant brain: A study of developmental trajectories

“…Axonal pruning is a well known developmental program in which axonal outgrowths are eliminated during maturation in a competitive manner in which axonal boutons compete for neuronal connections. This pruning facilitates proper neuronal wiring of the brain (Awasaki and Ito, 2004;Watts et al, 2004;Raff et al, 2002) and is important for proper neural development in prenatal or immature forms in both vertebrates and invertebrates (Oland et al, 1999;Bagri et al, 2003, Bishop et al, 2004Broadie, 2004). It has also been proposed that axonal pruning is the basic mechanism for adapting and/or preparing the brain for the external environment (Kantor and Kolodkin, 2003;.…”