Expression of Gva-ParaHox in the posttorsional larval stage. (A) SEM of pretorsional veliger larva. (B-D) Gva-Gsx is expressed in the area of the mouth opening (yellow arrow heads), apical ganglion (grey arrow heads), and ventral part of the digestive gland (blue arrow heads). (E-F) Gva-Gsx expression is detected in the buccal cavity in the forming radula anlage at onset of competence (yellow arrow heads). The gene is also expressed in the forming cerebral ganglia (red arrow heads). (G-J) Gva-Xlox is expressed in the digestive gland (blue arrow heads) and 6-7 cells of the ventral neuroectoderm (black arrow heads). The area marked by black rectangles in (G) and (H) is shown in higher magnification in (I). A section through the digestive gland is shown in (J). Note that the section is not medial since the digestive gland is located on the left side of the larva. (K-L) Gva-Cdx is expressed in the hindgut (blue asterisk) and weaker in the digestive gland (blue arrow heads). ag apical ganglion, at apical tuft, cg cerebral ganglion, e eye, f foot, m mantle edge, mc mantle cavity, mo mouth, o operculum, pv prevelar area, sc sensory cups, v velum, y yolk.