Odotopic afferent representation of the glomerular antennal lobe organization in the mushroom bodies of ants (Hymenoptera: Formicidae): Comparisons between two species

Abstract

In this work, the organization of the antennal lobes (ALs) and its topographic representation in the mushroom bodies (MBs) in soldiers of two species of ants has been compared. Morphologic comparison between these species suggests that ALs of A. mexicana could be more specialized than that of C. ocreatus at the expense of general capabilities. In both species the AL is organized in six groups of glomeruli, each of which innervated by its own tract. Glomeruli clusters are grouped in two regions, anterior and posterior, by the innervation of projection neurons (PNs) that connect AL with MBs via antennoprotocerebral tracts (APT). Calyces of MBs are layered and receive segregated olfactory information: PNs innervating anterior glomeruli clusters send axons through lateral-APT to the lateral horn (LH) and then to inner layer of the calyx, while PNs innervating posterior glomeruli clusters send axons through medial-APT to inner layers of the calyx and then to the LH. These results show that AL organization is topographically represented in the MB forming a coarse odotopic map. The two pathways connecting AL with MB could represent two channels for processing different kinds of odors or different properties of olfactory stimuli. The neuroanatomical results suggest a conserved functional organization in social hymenopterans.