Investigated morphological features of different semaphoronts of
(Peracarida). External morphology and developing nervous system of N. integer. (a) Semaphoront Ni EN, showing buds of the first and second antenna [A1/A2], but not the mandible. (b) Semaphoront Ni Naup-d showing mandible buds and postnaupliar appendage anlagen from the first maxilla to the fifth thoracic segment [Md], [Mx1], [Mx2], [T1]. (c) Semaphoront Ni I. The full set of segment anlagen is present, including the sixth pleomere. (e) Magnified lateral view of same semaphoront showing the posterior trunk and telson anlage. Appendage buds are visible down to the second pleomere. (d) Same semaphoront, showing phalloidin signal in naupliar ganglia [NGA]. (f) Semaphoront Ni II. Faint ganglion anlagen are visible also in the first and second maxillary segment [mx1-g], [mx2-g ]. (g) Semaphoront Ni III, with ganglion anlagen observable also from the first thoracomere [t1-g] down to the seventh thoracomere. The more anterior neuromeres show extensive formation of nerve fibers. The phalloidin signal also shows developing musculature. (a, e) blend projection, (b, c) normal shading projection of nuclear signal (TOPRO-3) from confocal image stacks (cyan). (d, f) Maximum intensity projections of phalloidin-signal (green). (g) Maximum intensity projections of phalloidin-signal (green), acetylated alpha-tubulin signal (red), and nuclear signal (TOPRO-3), (blue). Abbreviations: Ol optic lobes, A1–P6 appendage anlagen of respective segments, T telson anlage, pc protocerebrum, dc deutocerebrum, tc tritocerebrum, md-g–p6-g ganglion anlagen of respective segments, lonb longitudinal neurite bundles, lmp longitudinal muscle precursor, CP caudal papilla. Scale bars 100 μm in all panels.