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Fig. 9 | BMC Biology

Fig. 9

From: The visual pathway in sea spiders (Pycnogonida) displays a simple serial layout with similarities to the median eye pathway in horseshoe crabs

Fig. 9

Immunolabeling in sense organs and protocerebral structures in Nymphonidae. Nymphon gracile (AE,H,I) and N. cf. multituberculatum (F,G). A 3D-reconstructed volume rendering of protocerebral sense organs and the brain, μCT scan, lateral view. Stippled brackets indicate the positions of the sections shown in BG. BI Extended optical sections of immunolabeled samples (MIP). B,C Tubulin (TUB, magenta) and histamine (HIS, green) with nuclear counterstain and autofluorescence (AF + NUC, gray), horizontal sections. Note strong histamine labeling in the eyes’ retinae (C), and absence of signal in the lateral sense organ (B,C). D Histamine (green) with nuclear counterstain (gray), horizontal section. The R-cells send their histamine-ir axon terminals into the visual neuropil. E Serotonin (5HT), horizontal section. Arrows indicate somata of selected ventral neurons projecting through the broad antero-median tract to the arcuate body. F,G Tyrosine hydroxylase (TH, magenta) and serotonin (green, shown only in F). Arrows indicate TH-ir somata of selected antero-ventral type 2 neurons. White arrowheads point to selected, weakly TH-ir somata of anterior type 1 neurons. Note complementary TH and serotonin labeling in the arcuate body layers. Light blue arrowheads mark TH-ir somata of dorsal neurons with primary neurites projecting around the arcuate body and extending posteriorly (not shown). H,I Orcokinin (ORCO, green), synapsin (magenta) and tubulin (gray), para-sagittal and mid-sagittal sections (H and I, respectively). The arrow indicates orcokinin-ir somata of two anterior neurons with primary neurites (arrowheads) projecting toward the antero-median tract (H) before looping into the orcokinin-ir antero-median neuropil (I). The asterisk (H) marks a tubulin-rich spherical body in the anterior soma cortex. Abbreviations: AB – arcuate body; AE – anterior eye; AMN – antero-median neuropil; AMT – antero-median tract; BR – brain; BRN – brain neuropil; CHNV – cheliphore nerve; DPL – dorso-posterior lobe; LO – lateral sense organ; PE – posterior eye; PNV – proboscis nerve; RTA – R-cell axons; VN – visual neuropil

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