Fig. 4

Colocalization of potential neurotransmitters and neuropeptides in apical cells of infusoriform larva. Immunostaining signals of potential neurotransmitters and neuropeptides appear in apical cells of infusoriform larva, GABA (a), dopamine (b), dopamine beta hydroxylase (c), vasopressin (d), and oxytocin (e). Dopamine beta hydroxylase is also expressed in urn cells (c) inside the infusoriform larva. These results suggest that apical cells are likely the signal transduction center to receive environmental signals and to coordinate the release of germinal cells. Nuclei were labeled with DAPI (blue), and acetylated tubulin antibodies were used to label cilia (yellow). a, apical cell