The antennal lobe of orthoptera - Anatomy and evolution

The first odor-processing neuropils of insects comprise glomeruli, islets o f neuropil, that are supplied by olfactory receptor neurons and give rise t o efferent axons to higher brain centers, Glomeruli size and organization v aries in a taxon-specific manner across the Insecta, suggesting possible co rrelates between their organization and chemosensory behaviors in different insect groups. Comparative studies of antennal lobe glomeruli within the O rthoptera have been used to infer how the various taxon-specific arrangemen ts of odorant-processing structures (glomeruli) might have evolved. The cel lular arrangements in glomeruli have been surveyed using anterograde fillin g and Golgi impregnation of antennal receptor neurons projecting to the ant ennal lobe in Stenopelmatidae, Tettigoniidae, Gryllidae, Tetrigidae and Acr ididae. These taxa, which represent the two suborders of Orthoptera, reveal a high correlation between the neural architecture of the glomeruli and st ructures within the glomeruli, Using a recent molecular phylogeny of the Or thoptera we have mapped the occurrence of glomerular characteristics to inf er the evolution of antennal lobe structures in orthopterans. The functiona l implications of these results are discussed. Copyright (C) 2001 S. Karger AG, Basel.