Fig. 4
From: Development of the nervous system in Platynereis dumerilii (Nereididae, Annelida)
Development of 5-HT-like (green) and acetylated tubulin-like (red) immunoreactivity in P. dumerilii. Protrochophore (a), early trochophore (b,c), mid-trochophore (d), early metatrochophore (e,f), mid-metatrochophore (g), early nectochaete (h), late nectochaete (i,j). a: 17 hpf, caudal view on the first posterior 5-HT-lir cell (sp) with two basal fibers (arrows). b: 20 hpf, the first posterior 5-HT-lir cell with two basal fibers (arrows) and two apical cilia (arrowhead) in the centre of the open-circuited telotroch ring. c: 20 hpf, apical view on the first apical 5-HT-lir cell (sa1) with two short fibers (arrowheads) running at the base of the horseshoe-shaped apical ciliary tuft, and the long fibre running towards the prototroch (arrow). d: 24 hpf, ventral view showing the cells sp., sa1 and sa2, and 5-HT-lir fibres labelling the apical neuropil (arrowhead), prototroch nerve (arrows) and paired ventral cords (open arrows). Inset: 28 hpf, apical view showing the cells sa1 and sa2 (arrows). e: 44 hpf, ventral view showing four 5-HT-lir cells sa1–4 (arrows) around the apical neuropil (arrowhead) and two ventral cells (sv1 and sv2) near the ventral cords (open arrows). f: 44 hpf, high magnification of the posttrochal body part showing the posterior cell sp. and two ventral cells sv1 and sv2 (arrows) with their fibres running into the ventral cords crosswise. g: 46 hpf, ventral view showing 5-HT-lir cells associated with the ventral cords (arrows), transversal nerves (arrowheads) and the right dorsolateral longitudinal nerve (open arrow). h: 68 hpf, ventral view showing 5-HT-lir neurons in the developing brain (br), ventral nerve cord (arrows), and neurites in the head and segmental nerves (arrowheads). i: 3.5 dpf, ventral view showing 5-HT-lir neurons and neurites in the central and peripheral nervous system; asterisk - cerebral ganglion; arrows - ganglia of larval segments. j: 3.5 dpf, ventral view on the head region showing 5-HT-lir neuropil in the brain (asterisk) and innervation of the pharynx (ph). cc – circumoesophageal connectives. Scale bars = 20 μm