Fig. 1

The papillae of Ciona larvae. a A Ciona robusta (intestinalis Type A) larva, showing the 3 papillae. b Larva electroporated with the reporter plasmid CryBG > Unc-76::GFP (Cirobu.REG.KhS605. 16,789–17,833, Shimeld et al., which labels axial columnar cells (ACCs) and unrelated otolith cell. This larva is a transgenic mosaic, so the left dorsal papilla is unlabeled. The ventral papilla is also unlabeled but out of focus. c Magnified view of labeled papilla in b, without brightfield overlay, showing ACCs labeled by CryBG > Unc-76::GFP expression. Each has a characteristic apical, finger-like protrusion that extends through a fenestration of the larval cellulose tunic around the apical tip of the papilla. d Cartoon diagram of the major cell types of the three papillae and their approximate arrangement in the larva. Cell types are identified by color code and described in reference [121]. Cells of unknown number and type in between the three papillae are represented in white. Sizes not to scale