Figure 6

Ci-Syn expression at the neurula and tailbud stages. Whole mounts in side view, except for A, C in dorsal view, anterior is to the left. Cross sections viewed from the caudal end of the animal. Scale bars = 50 μm in whole mounts; 20 μm in cross sections. A, B: Mid-neurula stage embryos in dorsal (A) and lateral (B) view. Ci-Syn signal is present in two lateral spots (arrows) located posterior to the neuropore (np). C: Dorsal view of a late neurula embryo. The two Ci-Syn positive spots (arrowheads) are closer to the midline than in the previous stage. D: Lateral view of an initial tailbud embryo. Four bilateral symmetrical spots (arrowheads) are aligned along the posterior dorsal midline. E-K: Mid-tailbud embryos. E: Lateral view. Ci-Syn expression is found in the sensory vesicle, in the visceral ganglion and in some cells near the posterior end (arrow). In front view embryo (F) and in cross sections through levels shown in E (G, H), it appears that, in the sensory vesicle, positive cells are aligned along the posterior floor (arrow) and are present in the anterior roof in bilateral symmetrical spots (arrowheads). I: Cross section at the level of the visceral ganglion as indicated in E. J: Enlarged view of E showing the positive dorsal neurons near the tip of the tail. K: Superimposition of in situ hybridization with DAPI staining. Four nuclei are visible in correspondence of Ci-Syn signal in the posterior sensory vesicle and eight nuclei are present in the visceral ganglion. A single nucleus is visible in correspondence of the dorsal signal in anterior dorsal sensory vesicle. L-O: Prehatching larvae. M, O: Ci-Syn transcripts are present in posterior sensory vesicle, in fibers connecting the sensory vesicle to the visceral ganglion (arrow), in cells of the visceral ganglion (arrowhead). white asterisk, pigment cell of otolith; red arrowheads, pigment cell of ocellus.