Cyp26 function is required for patterning the amphioxus pharynx. The anterior portions of larvae at 36 hours post fertilization (hpf) are shown in lateral views (with anterior to the left). The 50-μm scale bar in (A) is applicable to the entire figure. Control larvae are shown as well as those treated with 5 × 10-7 M R115866 (a Cyp26 inhibitor) at the onset of gastrulation. The assayed genes are amphioxus Pax1/9 (A), (A’), Six1/2 (B), (B’), Tbx1/10 (C), (C’), Pax2/5/8 (D), (D’) and Pitx (E), (E’).