Fig. 13

Expression of Ino-Gsx during late development of the cephalopod Idiosepius notoides. Dorsal (d)–ventral (v), anterior (a)–posterior (p), and left (l)–right (r) axes indicate the orientation. Yolk sac removed in a–e. a Cephalic region of a stage 25 individual which expresses Ino-Gsx widely in the supraesophageal mass including the inferior frontal (if), anterior basal (ab), dorsal basal (db), dorsolateral (dl), and precommissural lobes (pc). Ino-Gsx expression is also observed around the eyes (arrowheads). b Same specimen as seen in a with Ino-Gsx expression around the eye (arrowhead), with faint expression on the lateral sides of the buccal region (arrow) and in the optic lobes (double-arrowhead). Note the lack of Ino-Gsx expression in the middle subesophageal mass (ms). c Same specimen as seen in a and b with Ino-Gsx expression in the posterior subesophageal mass (ps) but not in the middle subesophageal mass. Note the lack of Ino-Gsx expression in the vertical lobe (arrow) that is the anterior-most brain region. d Ino-Gsx is strongly expressed in the supraesophageal mass of stage 26 individuals including the peduncle lobes (pd) (here only cephalic region visible). Note the Ino-Gsx expression domain around the eyes (arrowheads). e Same specimen as seen in H with strong expression in the optic lobes and, among others, in the median basal lobes (mb). Note the strong Ino-Gsx expression on the lateral sides of the buccal mass (arrows). f Stage 28 individuals up to hatchlings express Ino-Gsx in the circular domain around the eyes (arrowhead); however, expression is lacking in the CNS. Note the unspecific staining in the statocysts. g Optical section along the sagittal plane of the same specimen as shown in j. No Ino-Gsx expression is visible in the supraesophageal (sp) or subesophageal masses (sb) of the CNS. Note the unspecific staining in the statocysts. ar arm, bm buccal mass, ey eye, fn funnel, mo mouth, o optic lobe, y yolk. Scale bars a–e 150 µm and f, g 200 µm