AmphiLim1/5 expression in developing amphioxus. Whole mount side views with anterior toward left. Sections are viewed from posterior end of animal. Whole mount and section scale lines respectively 50 μm and 25 μm. A) Blastula with expression in animal hemisphere. B) Mid-gastrula in blastopore view with expression in dorsal quadrant. C) Section in plane of dashed line in B; expression in ectoderm and dorsal mesendoderm (arrow). D) Side view of late gastrula with expression in neural plate and in posterodorsal mesendoderm. E) Section through a in D showing expression in neural plate. F) Section through b in D showing expression in dorsal mesendoderm. G) Side view of mid-neurula with expression in central nervous system, hindgut, rudiment of Hatschek's right diverticulum (asterisk), and first somite on left side (arrow). H) Section through a in G showing expression in anterior neural plate, epidermis on left side, Hatschek's right diverticulum (single arrow), but not in Hatschek's left diverticulum (twin arrow). I) Section through b in G showing expression on epidermis on left side and in most anterior somite on left side (arrow). J) Section through c in G showing expression in hindgut, but not in notochord (arrow). K) Dorsal view of mid-neurula showing expression in central nervous system, hindgut, and first somite on left side (arrow). L) Side view of early larva with expression in cells of dorsal nerve cord, rostral coelom (single arrow), Hatschek's nephridium (twin arrows), mesoderm associated with rudiment of second gill slit (asterisk), and neurenteric canal (arrowhead) of tail bud. M) Section through a in L showing expression in ventral and lateral cells of central nervous system and in rostral coelom (arrow). N) Section through b in L showing expression in ventral and lateral cells of central nervous system, in epidermis on left side, but not in Hatschek's left diverticulum (arrow). O) Section through c in L showing expression in epidermis on left side and in wall of Hatschek's nephridium (arrow). P) Section through d in L with expression in mesoderm cells near rudiment of second gill slit. Q) Side view of anterior end of later larva with expression in Hatschek's nephridium (single arrow) and in epidermis bordering upper lip of mouth (twin arrows). R) Section through a in Q, at level of mouth (arrow), showing expression in upper lip epidermis and in underlying Hatschek's nephridium.