Anatomical identification of glomeruli in the antennal lobes of the male sphinx moth Manduca sexta

Abstract

Computer-assisted neuroanatomical methods have been used to demonstrate unique identities of the glomeruli of the antennal lobes (ALs) in males of the sphinx moth Manduca sexta. The glomerular neuropil consists of the male-specific macroglomerular complex, which comprises two closely apposed bulky subunits, and 64 +/- 1 "ordinary" glomeruli arrayed in a shell around a central region of coarse neuropil. Computer-generated maps show the exact locations of all glomeruli and adjacent groups of neuronal somata in a constant Cartesian coordinate system, such that these can be accurately identified in any individual. The glomeruli belong to three classes according to the number and type of identification criteria they satisfy. The larger class comprises glomeruli (n = 44) identified only in the computer-generated maps on the basis of their relative positions. The other two classes include glomeruli that were also identified in sections, either directly from their proximity to readily identifiable structures and their shape and size (n = 10, including the labial-palp-pit-organ (LPO) glomerulus), or indirectly from their positions relative to the former (n = 9). Two very small glomeruli were present in only one AL, demonstrating the existence of anomalous glomeruli, whereas another glomerulus had no homologue in both ALs of one individual. The true number of ordinary glomeruli (per male AL) was thus estimated to be 64. The uncertainty in delineating some glomeruli might affect this number without implying modification of the homologies proposed. The locations of tracts and cell groups, both within and near the AL, are also invariant with respect to glomeruli, as shown in the computer maps. The methods employed are general and might be useful to researchers in related fields. The results obtained call for more attention to the precise geometry of neural structures.

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

“…These were the largest of the "ordinary" glomeruli: G20 (light blue glomerulus in Figs. 2E,E′,F,F′, 3), which lies posteromedial to the MGC (Rospars and Hildebrand 1992), the LPOG (yellow glomerulus in Figs. 2D,D′,E,E′, 3), which corresponds to G64 and has been extensively described by Kent et al (1986Kent et al ( , 1999 and Guerenstein et al (2004), and two anteriorly located glomeruli that we have named disc and discbase, which might correspond to G27/28 and G22/29 (dark red and green glomeruli, respectively, in Figs.…”

Morphological characterization of the antennal lobes in the Mediterranean fruit fly Ceratitis capitata

“…Knowing the spatial arrangement of glomeruli thus becomes a relevant step in elucidating the olfactory system of a particular species. For this reason, the glomerular organizations of the ALs have been studied and described in several insect species, such as Drosophila (Stocker et al 1990;Laissue et al 1999), moths (Kanzaki et al 1989;Rospars and Hildebrand 1992;Berg et al 2002;Skiri et al 2005), honeybees (Galizia et al 1999), mosquitoes (Anton and Rospars 2004;Ignell et al 2005;Ghaninia et al 2007), cockroaches (Chiang et al 2001) and beetles (Dreyer et al 2010;Hu et al 2011). This development has been strongly aided by the improvement of staining techniques based on fluorescent dyes, combined with confocal sectioning of whole-mount preparations, and the reconstruction of entire ALs by image analyses.…”

Chemosensory Selectivity of Output Neurons Innervating an Identified, Sexually Isomorphic Olfactory Glomerulus

“…One, analogous to the "main" OB of vertebrates, has 60 sexually isomorphic glomeruli that process information about volatile compounds associated with food and possibly other odors. The second subsystem, analogous to the "accessory" OB of many vertebrates (for review, see Brennan and Keverne, 2004), comprises three sexually dimorphic glomeruli (Rospars and Hildebrand, 1992). In males, these specialized glomeruli belong to the macroglomerular complex (MGC), and in females they comprise two large glomeruli [medial and lateral large female glomeruli (LFGs)] and one smaller glomerulus.…”