Fig. 6
Six3/6 expression in hoplonemertean and pilidiophoran larvae. a Six3/6 is expressed in anterior invaginations of invagination-stage P. californiensis larva. Arrows indicate paired anterior invaginations. Asterisk indicates apical organ. Inset at lower right shows focal plane near the surface of another invagination-stage larva. Paired surface expression near posterior end marked by black arrowheads. b Six3/6 expression in rudiment-stage larva, showing some diffuse subepidermal expression and strong expression near the apical plate. c Six3/6 is expressed in cephalic discs (cd) and apical organ of head-and-trunk-stage M. alaskensis pilidium larva. gt gut, cd cephalic disc, cb ciliated band, td trunk disc. Inset shows close-up of mid-plane of the apical organ, showing expression along the rim of the apical plate.