Fig. 1

The vascular anatomy of the larval swimbladder. (A - B) Erythrocyte-specific RFP expression (white arrowheads) and swimbladder EGFP expression in Et(krt4:EGFP)^sq33-2 xTg(gata1:dsRed)sd2 double transgenic larvae at 48 hpf, showing the active circulation in the vicinity of the developing swimbladder bud. (C - D) Blood circulation and swimbladder bud at 72 hpf in Et(krt4:EGFP)^sq33-2 × Tg(fli1:EGFP)^y1 (C) and Et(krt4:EGFP)^sq33-2 x Tg(gata1:dsRed)sd2 (D) double transgenic larvae. A pair of swimbladder artery (sba), as visualized by the GFP expression, could be seen to develop towards the swimbladder bud from both lateral sides in (C). (C′, D′) 2x magnification of the boxed regions in (C) and (D), respectively. Blood circulation was present in this vessel as observed in Et(krt4:EGFP)^sq33-2 x Tg(gata1:dsRed)sd2 double transgenic larvae (D). (E - F) Blood vessels (rete mirabile) in the swimbladder in Et(krt4:EGFP)^sq33-2 x Tg(fli1:EGFP)^y1 (E) and Et(krt4:EGFP)^sq33-2 x Tg(gata1:dsRed)sd2 (F) double transgenic larvae at 108 hpf. Each swimbladder artery contains two main countercurrent vessels formed through looping at the caudal end of the swimbladder (circular arrows in E). Blood circulation could be observed in the rete mirabile in Et(krt4:EGFP)^sq33-2 x Tg(gata1:dsRed)sd2 double transgenic larvae (white arrows in F). (G) A close-up view of the network of swimbladder vessels at 125 hpf. Direction of blood flow in these vessels is indicated by white arrows. Abbreviations: ama, anterior mesenteric artery; da, dorsal aorta; g, gut; sb, swimbladder; sba, swimbladder artery; siv, supra-intestinal vessel. Scale bars: 250 μm in (A-F), 100 μm in (G).