Figure 2

Neurogenesis in Axiothella rubrocincta. Confocal micrographs showing tubulinergic (green) and serotonergic (red) immunoreactivity. Anterior faces upwards (A-D) or leftwards (E-J). Scale bars: 150 μm (A-B), 75 μm (C-E), 150 μm (F-J). (A-C) Late larva. (A) Dorsal view with cerebral ganglion (cg) established. (B) Right lateral view. Circumesophageal connectives (cc) link the ventral neurite bundle (vnb), with associated ventral perikarya (v-sp) and segmental neurites (arrows), to the cerebral ganglion (cg) and the dorsal perikarya (d-sp). (C) Enlarged anterior part of B with peripheral neural network (pnn). (D-E) 4-setiger stage, right-lateral view. (D) Enlarged anterior part of E. A stomatogastric projection (stp) branches off from the right connective (cc). (E) The cerebral ganglion (cg) shows a ventral (vl-cg) and a dorsal lobe (dl-cg). Two segmental neurites (1 and 2, arrows) innervate the head. Up to four neurites (lines) are present in the following segments. A stomatogastric nerve ring (str) surrounds the pharynx. (F) 4-setiger stage, ventral view. The ventral neurite bundle (vnb) comprises a median (me) and a paired main (ma) strand. (G-J) 7-setiger juvenile, ventral view in G-I and right-lateral view in J. (G) Note the anterior proboscis neurites (apn). (H) Same individual as in G. (J) The segmental neurites (arrows) form a ring [inset; 3D reconstruction; red (vnb): ventral neurite bundle, green (e): esophagus, yellow (arrow): ring neurite]. anus (a), apical cilia (ac), intestine (i), nephridioducts (triangles), neurotroch (nt), nuchal neurite (nn), pharynx (ph), posterior cilia (pc), protonephridium (pn), prototroch (pt), telotroch (tt), setae (s), uncini (dots).