Development of the vasculature of the pectoral fin in the Australian lungfish, Neoceratodus forsteri

The development of the vasculature of the pectoral fin in the Australian lungfish, Neoceratodus forsteri, was studied by the dye-injection method. Only a single primitive subclavian artery appears from the dorsal aorta for the fin anlage, and it passes laterally through the postaxial region of the structure. The venous channel draining into the posterior cardinal vein is located in the preaxial region medially. As development proceeds, the arteriovenous arrangement in the pectoral fin anlage changes as follows: 1) one artery and one venous plexus, 2) two arteries and one vein, 3) three arteries and one vein, 4) four arteries and one vein, 5) three arteries and two veins, and 6) two arteries (radial and ulnar) and three veins (radial, ulnar, and ulnar marginal). The fin anlage through embryonic first rotation has gradually changed its postaxial margin to face dorsally and its preaxial margin to face ventrally. The second rotation causes the original preaxial margin to become dorsal and the original postaxial margin to become ventral. As a result, the radial and ulnar arteries are observed in the dorsal and ventral regions, respectively, in the medial side of the fin instead of in the lateral side as seen in the previous stage.