Expression of monoaminergic markers in C. intestinalis embryos. Lateral (a, c, e, g, i, k, anterior to the right) and dorsal views (b, d, f, h, j, l, anterior to the right) of late-tail-bud-stage embryos. (a, b) β-galactosidase activity driven by the CiTH cis-regulatory sequence (pCiTH-LacZ) (dopamine cells) is detected in the ventral sensory vesicle. (c-l) In situ hybridization of the indicated probes. White arrows point to the pigmented otolith. (c, d) CiGch is expressed in two domains, one corresponding to the CiTH expressing cell population within the sensory vesicle and the other to the CiTph territory flanking the trunk ganglion (small black arrows). CiAadc-a (e, f) and CiSERT (g, h) are expressed in the CiTH domain, while CivMat-a (i, j) is expressed at the same location as CiTph, outside of the nervous system (small black arrows). To accurately localize these transcripts, we used CiNut (k, l) as a pan-neural marker expressed in the CNS including the sensory vesicle (SV) and the trunk ganglion (TG). Sense probes gave no signal (data not shown). Scale bar = 20 μm.