Ino-POU3 -expression during development of I. notoides . The cartoon highlights Ino-POU3-expression as black checkered domains (see Figure 1 for color-coded ganglia). Dorsal (d)-ventral (v), anterior (a)-posterior (p), and left (l)-right (r) axes indicate the orientation. Staining around shell gland is unspecific (C, D, F, G). (A) During stage 19 Ino-POU3 is expressed in the cerebral (cg) and palliovisceral ganglia (pvg). (B) Same specimen as shown in A expressing Ino-POU3 in the mantle (arrowheads). (C) Stage 22 individuals express Ino-POU3 in the pedal (pg) and palliovisceral ganglia, the eyes (e), and the anterior basal lobes (arrowheads in lower inset). D-G: Optical sections from dorsal to ventral of a stage 24 individual (unspecific staining in the beak (bk)). (D) Ino-POU3 is expressed in the brain including the peduncle lobe (arrowhead in inset). (E) Close-up of the supraesophageal and posterior subesophageal masses (psm). The anterior basal (ab), posterior basal (pb), and precommissural lobes (pc) express Ino-POU3. (F) The interbasal lobes (it) connect to the subesophageal mass and express Ino-POU3. (G) Ino-POU3-expression in the anterior (asm) and middle subesophageal masses (msm) and in the ventral magnocellular lobes (vm). (H) Ino-POU3-expression in the superior (sb) and inferior buccal lobes (ib) but not in the vertical lobe complex (arrowhead) during stage 25. The statocysts are labeled with an asterisk. (I) During stage 25 Ino-POU3 is expressed in the intrabrachial ganglia (arrowheads), the dorso-lateral (dl), the peduncle (pd), the superior frontal (sf) and inferior frontal lobes (if). (J) During stage 26 Ino-POU3 is expressed in the brain including the inferior buccal (ib) and superior buccal lobes (sb) but not the vertical and subvertical lobes (arrowhead). (K) Weak Ino-POU3-expression during stage 27. Abbreviations: a, arm; bm, buccal mass; es, esophagus; f, funnel; m, mantle; ol, optic lobe. Scale bars: A-G: 150 μm, H-K: 200 μm.