Expression pattern of Tbx20 in Xenopus tropicalis.The expression pattern of Tbx20 detected by in situ hybridization between late neurula and early tadpole stages is shown (embryos uncleared). a– o: Stages are as follows: stage 20 (a– c), stage 25 (d,e), stage 29/30 (f), stage 33 (g–i), stage 36 (j–l), and stage 40 (m– o). Ventral views are shown in i, l, and o. Except for the anterior view in a, embryos are oriented with anterior to the left. a, atrium; cg, cement gland; hb, hindbrain; hp, heart primordium; ht, heart tube; sv, sinus venosus; v, ventricle.