Fig. 6

Distribution and projection pattern of histaminergic neurons in the ventral nerve cord of Glomeris marginata. Maximum projections of cLSM stacks (ventral view, anterior to the top). a Overview of the ganglia 10–12 (G10–12), illustrating the rather homogenous structure of the ventral nerve cord. The ganglia could be distinguished from the connectives by the segmental nerves (SN). The ganglia contained the anteromedial cell bodies (AMC) as well as a conspicuous triangular neuropil, revealed by dense histamine-immunoreactivity (asterisks). A strongly labeled longitudinal tract could be observed throughout the ventral nerve cord (double arrowhead). b, c Besides the AMC, each ganglion contained a posterolateral soma pair (PLC). The three AMC can be subdivided in a single cell (AMC1) and two closely associated cells (AMC2 + 3). All AMCs projected laterally and posteriorly into the triangular neuropilar structure (black arrows in b and c). In rare cases, the AMC1 performed a loop, growing first posteriorly, but then looping back anteriorly before its signal got lost (black arrowheads in b). d The PLC projected anterolaterally toward the center of the ipsilateral hemiganglion (black arrows; ganglionic midline indicated by dashed line). e Reconstruction drawings of selected histaminergic neurons in a ganglion of the ventral nerve cord. The triangular histamine-immunoreactive neuropil is highlighted in grey. Abbreviations: AMC1–3: anteromedial cell bodies 1–3; G10–12: ganglion 10–12; PLC: posterolateral cell bodies; SN: segmental nerve. Scale bars: a: 100 μm; b-d: 25 μm