Fig. 5. Lophotrochin and trochin expression in lophophorates: brachiopods and phoronids.

a–f The lophotrochin and trochin expression in brachiopod Terebratalia transversa. a Lophotrochin (purple) is expressed apically in the region where the ciliary tuft forms. b Expression of trochin (purple), also in the region where ciliary tuft forms. c In later stage larvae, lophotrochin expression is specific to the ciliary band. d Expression of trochin in later larval stage is also specific to the ciliary band. e Diagram of the larva, based on (c). Cilia are highlighted in green. f Confocal image with nuclei (magneta, Hoechst) and cilia (green, anti-acetylated tubulin) showing that the nuclei of cells underlying the prototroch-like ciliary band are deep beneath the surface, in a similar location to the in situ probe signal. Note that the ectoderm is covered with short cilia. g–j The expression of lophotrochin in phoronid Phoronopsis harmeri. g, h In Phoronopsis’s four-tentacle stage larva, lophotrochin expression (purple) is observed in the telotroch and along the ciliary band spanning the larval tentacles. g posterior view, h lateral view. i Expression becomes stronger in the tentacles as development proceeds, and in the ten-tentacle stage, expression is strongest in the tips of the largest tentacles, and the telotroch, expression is also found in the ciliated cells at the edge of the preoral lobe (or hood) and in the apical organ. j Diagram of the actinotroch larva showing ciliary structures (apical organ, edge of the preoral lobe, the main ciliary band spanning lophophore tentacles, and telotroch) highlighted in green. Scale bars: 100 μm. For each in situ hybridization, at least 20 animals were stained and all had the pattern shown.