Fig. 9
Development of the trunk nervous system in post-metamorphic juveniles of O. fusiformis (~28 dpf). FMRFamide-LIR (yellow) and 5-HT-LIR (purple), aTub-LIR (cyan), DNA (dark blue) (except for inset (C) where DNA staining is shown in grey). Confocal z-projections. Anterior is left in all images, except of (c) where anterior is up. a and b are lateral views, (c–e) are views from ventral, (f) is a view from dorsal. Stages are given in days post fertilization (dpf). The shape of the esophagus (and intestine) is indicated by white lines. The position of somata clusters showing 5-HT-LIR is indicated with white dotted rectangles. a Shortly after metamorphosis, at 28 dpf, 5-HT-LIR is present in the ventral nerve cord (vn), in numerous lateral nerves (ln) and prominent longitudinal nerves (lo). b Using the same specimen and orientation as in (A), the aTub-LIR reveals numerous lateral nerves (ln). c A ventral view at 28 dpf reveals serial clusters of somata (with 5-HT-LIR) and lateral nerves branching off from the ventral cord (vn) at the position of the cell clusters. The inset shows the region of the 2nd cluster of somata possessing 5-HT-LIR (marked with white asterisk in (C)) stained with DAPI. Notably, DNA staining does not show any cluster. d The ventral nerve cord (vn) is represented by two parallel neurites and a median nerve with FMRFamide-LIR (see left inset, nerves are labeled 1–3) and two outer parallel nerves only showing aTub-LIR (see right inset, nerves are labeled 4 and 5). At least nerves 2 and 3 arise in 5-HT staining as well (not shown). Nerve 1 is visible in some 5-HT stainings only. Notably, no serial clusters of somata showing FMRFamide-LIR are detectable along the ventral cord (vn). e aTub-LIR at 28 dpf reveals a pair of lateral longitudinal nerves (arrow head) running besides the main cord, and numerous lateral nerves (ln) leading towards the periphery. f 5-HT staining at 28 dpf shows serially arranged lateral nerves (ln) and numerous lateral perikarya. Furthermore, longitudinal nerves (lo) are running in antero-posterior direction. Note that the overlap of the 5-HT-LIR and the aTub-LIR causes a white color of the dorsal root of the circumesophaegal connective (dr). at, apical tuft; cc, circumesophageal connective; ch, chaetae; dr, dorsal root of cc; dpdr, dorsal part of the dorsal root of cc; dpvr, dorsal part of the ventral root of cc; en, esophageal nerve; es, esophagus; gl, gland; hg, hindgut; ln, lateral nerve; lo, longitudinal nerve; mg, midgut; sn, serotonergic neuron; vn, ventral nerve cord; vpdr, ventral part of the dorsal root of cc. Sale bars = 100 μm (A, B, D, E, F) and 50 μm (C). The scale bars only refer to the main images, not to the insets