Figure 7

Developmental expression of FoxA in Themiste lageniformis. (A, B) Vegetal views; (C, E, G, I, K, M, O) ventral views with anterior up; (D, F, H, J, L, N, P) corresponding lateral views with ventral side to the left, anterior up. (A) Two cells on the anterior vegetal face of the blastula express FoxA. (B) Same embryo and orientation as in (A). FoxA expression overlaps with Hoechst-labeled nuclei (white arrowheads). (C) Stage 3 expression within and lateral to the invaginating stomodeum (black arrow). (D) Same embryo as in (C), showing subsurface stomodeal expression (black arrow). (E, F) Early stage 4 embryo. FoxA expression in the stomodeum (black arrow), subsurface cells on ventral midline (white arrow) and within endoderm (broken black arrow). (G, H) FoxA expression in the stomodeum (black arrow) and subsurface cells on the ventral midline (white arrow). (H) Same embryo as in (G) showing expression in endoderm (broken black arrow) and putative hindgut tissue (white arrowhead). (I, J) Stage 5 embryo during transition to the pelagosphera larva. FoxA is expressed in the stomodeum (black arrow), ventral ectoderm cells (white arrow), and putative hindgut cells (white arrowhead). (K, L) Posterior elongation of the early larva with expression in the foregut (black arrow), ventral ectoderm (white arrow), midgut (broken black arrow) and presumptive hindgut (white arrowhead). Expression persists on the anterior side of the mouth (black arrowhead). (M, N) Stage 7 pelagosphera with FoxA expression in all previous domains. (O, P) Swimming pelagosphera at 3 days. FoxA is predominantly expressed in the esophagus (black arrow) and weakly expressed in the presumptive hindgut region (broken bracket). Asterisk marks position of the stomodeum. Solid brackets outline the anterior band of large prototroch cells. Similar arrow types (black, white, broken black) correspond with similar domains of FoxA expression.