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Fig. 15 | BMC Evolutionary Biology

Fig. 15

From: Comparison of ventral organ development across Pycnogonida (Arthropoda, Chelicerata) provides evidence for a plesiomorphic mode of late neurogenesis in sea spiders and myriapods

Fig. 15

Cell proliferation in palpal and ovigeral VOs of the second larval instar of T. orbiculare. Labeling of acetylated tubulin (white) and EdU (4 h exposure, red) with nuclear counterstain (blue). Horizontal (a, a’) and sagittal (b, c) optical sections, anterior to the top. Stippled ovals highlight the apically attaching early VOs of one body half. Stars indicate the forming apical invagination of the early VO stages, prior to their detachment from the apical ectoderm. a, a’: Note the low number of EdU-positive cells in the palpal and ovigeral VOs as opposed to the forming VO of walking leg neuromere 1. Black arrows mark the roots of the palpal and ovigeral larval nerves as they leave the larval subesophageal ganglion. Black arrowheads highlight the first longitudinal axonal pathways of the future VNC. b, c: Note the considerable size difference between the palpal and ovigeral VOs (c) and the invaginating VO of walking leg neuromere 1 (b). Abbreviations: cut – cuticle, ep – epidermis, pan – palpal neuromere, ovn – ovigeral neuromere, seg – subesophageal ganglion, wln1 – walking leg neuromere 1

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