Fig. 5

Serotonin-like immunoreactive (−lir) central nervous system of Galathowenia oculata. Labeling with anti-serotonin (red), anti-acetylated α-tubulin (green) and nuclear labeling with DAPI. Maximum projections (a, b, f–j) and optical sections (c–e) are shown. Whole-mount stained specimens (b–e), sectioned specimens with 100–200 μm thickness (a, f–j). a The serotonin-lir ventral nerve cord and circumesophageal connectives: frontal section, ventral view, anterior end is to the top. b The medullary organized ventral nerve cord, trunk region, ventrolateral view, anterior is to the top. c Serotonin-lir neurites of the ventral nerve cord in the posterior-most biramous segments, ventrolateral view, anterior is to the top. d, e Serotonin-lir elements of the head collar: ventral and dorsal views, respectively, anterior is to the top. f–h Serotonin-lir elements of the dorsolateral folds (arrows) and the inner wall of the head collar: frontal sections, ventral view, anterior is to the top. i Serotonin-lir elements (arrows) of the outer wall of the head collar: transverse section, ventral is to the bottom. j Sensory cells (arrows) in epidermis of the outer wall of the head collar: transverse section. bs – short biramous segments, cc – circumesophageal connectives, ccc – transverse neurites interconnecting circumesophageal connectives, cn – serially arranged circular neurite bundles, dc – dorsal commissure, dl – dorsal pygidial lobe, dlf – dorso-lateral folds, dn – main dorsal neurite bundle, exn – epidermal neurite plexus on outer side of head collar, hc – head collar, inn – neurite plexus within the inner side of the head collar epidermis, lln – main longitudinal neurite bundles of left body side, nc – notopodial capillaries, nu – neuropodial uncini, rln – main longitudinal neurite bundles of right body side, scn – serotonin-lir serially arranged circular neurite bundles, ss – serotonin-lir somata, vcs – serotonin-lir somata associated with the ventral nerve cord, vl – ventral pygidial lobes, vnc – ventral nerve cord