Fig. 3

Schematic representation of acetylated α-tubulin-LIR in Echinoderes. Only conserved traits across species are represented. For clarity, innervation and external arrangements of species-specific cuticular characters and head scalids have been omitted. Anterior is up in (a-b), dorsal is up in (c-g). a-b Overview of tubulinergic elements of the nervous system in (a) dorsal and (b) ventral views. Arrowheads in (b) mark the anterior-posterior axial positions of cross-section schematics in (c-g). c Introvert. Note the outer ring has 10 radially arranged longitudinal neurite bundles (× 10), the middle ring corresponds with the neuropil, and the inner ring shows 9 oral styles neurites (× 9), without the middorsal neurite (see legend). d Neck. e Segment 1 (arrows mark convergent longitudinal bundles). The two ventral bundles with black dots in (c-e) mark the unfused condition of the ventral nerve cord. f Segments 3–7. g Segment 8. Abbreviations: gn, gonad neurite; gon, gonopore neurite; lnb, longitudinal neurite bundle; ltasn, lateral terminal accessory spine neurite; mcnr, mouth cone nerve ring; ncn, neck circular neurite; nen, nephridial neurite; np, neuropil; osn, oral styles neurite; sdn, subdorsal longitudinal nerve; s1–11, trunk segment number; tn, transverse neurite; tsn, terminal spine neurite; vln, ventrolateral nerve; vnc, ventral nerve cord; vncn, ventral nerve cord neurite