Fig. 4

Expression of Hoxd13 in the cloacal region of catsharks. (A) Lateral view of pelvic fin region showing Hoxd12 expression at stage 25. Dashed lines mark the approximate planes of section showed in panels B and C. (B) Transverse section showing Hoxd12 expression in visceral mesoderm (Vm) and gut endoderm (Ge). Note absence of Hoxd12 expression in anterior part of the pelvic fin (Pl). (C) Transverse section showing Hoxd12 expression in the posterior part of pelvic fin and adjacent visceral mesoderm. Note absence of Hoxd12 expression in the gut endoderm. (D) Lateral view of the pelvic fin region showing Hoxd13 expression at stage 25. Note that Hoxd13 domain lies posterior to Hoxd12 domain (compare with panel A). Dashed lines mark the approximate planes of the section showed in panels E and F. (E) Transverse section showing Hoxd13 expression in the visceral mesoderm and gut endoderm. Note absence of Hoxd13 expression in the anterior part of pelvic fin. (F) Transverse section showing Hoxd13 expression in the posterior part of the fin, visceral mesoderm and ventral endoderm. Arrowheads mark expression in endoderm (contrast with absence of Hoxd12 in endoderm in panel C). (G) Transverse section throughout the pelvic fins at stage 30 showing Hoxd13 expression in the cloacal epithelium (arrowheads).