Additional file 2: of Comparison of ventral organ development across Pycnogonida (Arthropoda, Chelicerata) provides evidence for a plesiomorphic mode of late neurogenesis in sea spiders and myriapods

Movie of walking leg ganglion 3 in a juvenile of Meridionale sp. Labeling of acetylated tubulin (white), BrdU (green) and EdU (red) (4 h BrdU exposure, 92 h sea water, 4 h EdU exposure, 20 h sea water) with nuclear counterstain (blue). Different combinations of the four signals are shown during the movie to highlight specific aspects in more detail. The movie starts in ventral view, anterior is to the top. The object turns almost 90° around the a-p axis towards the left to demonstrate that the VOs containing the majority of the proliferating cells (as indicated by the BrdU+ and EdU+ nuclei) are located externally on the ventral surface of the ganglion. Only BrdU+ cells are found along the migratory streams that extend into the soma cortex. EdU+ nuclei are located exclusively in the external VOs, showing BrdU co-labeling. Note also the very prominent and curved ventral longitudinal tract that is visible whenever the tubulin signal is shown, e.g., during the rotation back into ventral view at the end of the movie. (MP4 16,957 kb) (MP4 16957 kb)