Expression patterns of P. flava ParaHox genes. In situ hybridization analyses of PfCdx (A-H), PfXlox (I-P), and PfGsx (Q-X) were performed on unfertilized egg (UF), blastula (B), early gastrula (EG), mid-gastrula (MG), late gastrula (LG), and tornaria larva (TL) at different time points (hpf, hours post fertilization; dpf, days post fertilization). White and black arrows indicate the expression of PfCdx and the midgut-hindgut boundary, respectively. Black and white arrowheads denote the expression of PfXlox and PfGsx, respectively. The observed views are indicated at the bottom right corner of the panels in the first row. Unless otherwise indicated, the observed views of subsequent panels are the same as the first panel in each column. DV, dorsal view; LV, lateral view; VV, ventral view. The scale bar is 50 μm. Panels T’ and U’ are the blastopore view (BV) of panels T and U, respectively.