Fig. 3
The central olfactory pathway of T. castaneum. a Backfill of one antenna (magenta) stains all glomeruli in the ipsilateral antennal lobe (AL) except one. This glomerulus is exclusively labeled by a backfill of a maxillary palp (cyan). b In addition to the AL glomeruli, backfilling (magenta) of one antenna labeled the ipsilateral antennal mechanosensory and motor center (AMMC), located n-dorsally to the AL, c as well as descending fibers to the gnathal ganglion (GNG). d Maximum intensity projection of the backfills of mouthparts (cyan) shows massive innervation of the GNG including the gnathal olfactory center (GOC) (magnified in the inset) and the primary gustatory center (PGC). e Backfill of the mouthparts (cyan) revealed in the cerebral ganglion beside innervation of a single ipsilateral AL glomerulus also projections in the ipsilateral lobus glomerulatus (LG). f Reporter expression of the partial Orco-Gal4/UAS-DsRed line (magenta) revealed two paired input tracts (black and white arrowheads) from the maxillary (white arrowhead) and labial palps (black arrowhead) that converge in a medial and n-anterodorsally located glomerular area, the GOC, and ascend to a microglomerularly organized area, the LG. See also Additional file 7: Movie S3. Orientation bars in (a) also apply for (b) and (e). AL antennal lobe, AMMC antennal mechanosensory and motor center, GNG gnathal ganglion, GOC gnathal olfactory center, L lateral, LG lobus glomerulatus, NA neuroaxis-anterior, PGC primary gustatory center, TR tritocerebrum