Fig. 7

Histaminergic neurons in the central nervous system of Chelifer cancroides. Maximum projections of cLSM stacks (ventral view, anterior to the top), showing immunoreactivity of histamine (green) and synapsin (grey). a, b Three protocerebral histaminergic neurons (PCC) per hemiganglion were identified in the protocerebrum: two PCC were positioned anterodorsally to the arcuate body (AB), one laterally to the AB. a’, b’ All PCC projected single neurites toward each other (black arrows), before turning posteroventrally. c Two pairs of immunoreactive cell bodies (OC) were identified in the fused opisthosomal ganglia. c’ A single contralateral projection arose from the OC (black arrows). d A conspicuous longitudinal immunoreactive tract projected throughout the length of the walking leg ganglia (white arrows). e A pair of histaminergic cell bodies (WGC) were found in the posterior regions of the prosoma, probably belonging to the walking leg ganglion 3. f Reconstruction drawings of selected histaminergic neurons in the central nervous system. Abbreviations: AB: arcuate body; OC: opisthosomal cell bodies; PCC: protocerebral cell bodies; PG: pedipalpal ganglion; WG1–4: walking leg ganglion 1–4; WGC: walking leg ganglion cell bodies. Scale bars: a–e: 50 μm; a’–c’: 25 μm