Fig. 4

The protocerebrum. a Frontal vibratome section at the mid-level of the protocerebrum, double-labeled against acetylated tubulin (yellow-red on the left, black-white inverted on the right) and RFamide (green on the left). A bundle of neurites connects the lobula with the lateral part of the central body (double-arrows). b-c Horizontal vibratome section of the first and second visual neuropils of the left brain hemisphere. b Maximal projection of acetylated tubulin-like immunoreactivity (black-white inverted) showing the outer chiasm between lamina and medulla (yellow arrow). c Single optical slice, triple-labeled against acetylated tubulin (yellow-red), histamine (green) and nuclei (blue, C1) as well as against histamine, separately (black-white inverted, C2). Histamine-like immunoreactivity is concentrated peripherally within the spherical subunits of the lamina (asterisks) and reveals a two-layered organization of the lamina (brackets in C2). d Sagittal vibratome section of the visual neuropils showing crossing neurites between lamina and medulla (outer chiasm) as well as between medulla and lobula (putative inner chiasm, yellow arrow), labeled against acetylated tubulin (black-white inverted). e Frontal view on the central body and the tracts w, x, y, and z, double-labeled against acetylated tubulin (yellow-red), RFamide (green, E1), as well as against acetylated tubulin, separately (black-white inverted, E2). Some neurites of z-tracts form chiasmata within the central body (single arrow). The double-arrow points to the bundle of neurites that connects the central body with the lobula. Insets (bottom left corner) show position and orientation of depicted sections in the brain. Abbreviations: ampn anterior medial protocerebral neuropil, cb central body, hn/tm hemiellipsoid body/ terminal medulla complex, la lamina, lal lateral accessory lobe, lo lobula, me medulla, pcc protocerebral commissure, pmpn posterior medial protocerebral neuropil, pnt projection neuron tract, w/x/y/z tracts, [numbers] somata cluster. Scale bars: (a-c) 50 μm, (d-e) 25 μm