ALO contains a network of blood and lymphatic vessels. (A–D) Confocal micrographs of an adult Tg(mrc1a:egfp)^y251, Tg(kdrl:mcherry)^y205 double transgenic zebrafish with mrc1a-positive lymphatics in green and kdrl-positive blood vessels in magenta. This animal was also injected intravascularly with a Hoechst 33342 dye, marking blood cell nuclei with blue fluorescence. Images include (A) an overview image of the head, with the position of the ALO noted; (B) higher magnification image of the area in panel A noted by an arrow, showing a network of blood (magenta) and lymphatic (green) vessels in the ALO, with blood circulation (blue) in blood vessels; and (C and D) higher magnification images of the area noted by an arrow in panel B, showing that blood vessels (magenta) but not lymphatics (green) contain circulating RBCs (blue). (E and H) Schematic diagram of procedure for intralobular (E) and anterior body (H) injection of quantum dots. (F, G, I, and J) Confocal micrographs of an adult Tg(mrc1a:egfp)^y251 zebrafish ALO after intra-organ injection of 705-nm quantum dots (Qdots), with mrc1a-positive lymphatics in green and Qdots in magenta. Panels F and I show an overview of the ALO vicinity, noting the higher magnification area shown in panels G and J. The lobe-injected (F and G) and body-injected Qdots (I and J) drain via lymphatics into an adjacent deeper large lymph sac at the base of the ALO, noted with a blue arrow in panels G and I. (K–M) Transmission electron micrographs of ALO vessels, showing an overview of adjacent vessels (K) and higher magnification images of vessel cell–cell junctions (L and M). ALO vasculature imaging, n = 8, with Hoechst, n = 2, ALO lobe lymphatic drainage, n = 5, anterior lymphatic drainage, n = 6. Scale bars = 1 mm (A), 500 µm (F), 200 µm (I), 100 µm (G and J), 50 µm (B), 25 µm (D), 5 µm (K), 300 nm (L and M).