Lymphangiography reveals lymphatic capillaries in early zebrafish development.

<p><b>A</b>, Subcutaneous injection technique employed for lymphangiography. The narrow red triangle represents the needle used to inject Texas Red-LMD into the zebrafish posterior tail. The black box demarcates the approximate region of the trunk imaged. <b>B</b> and <b>C</b>, Ideal lymphangiogram of 3-dpf <i>Tg(fli1:EGFP)^y1</i> zebrafish (green blood vessels). <b>B</b>, At 15 minutes post-injection (early-phase), green ISVs (large white arrows) are distinguished from extravascular collections of Texas Red-LMD at somitic boundaries (yellow arrowheads) and small red lymphatic vessels (small white arrows) deep to and within the somitic interspaces. <b>C</b>, At 4 hours post-injection (late-phase), Texas Red-LMD is still not present within ISVs (large white arrows); however, more of the small lymphatics contain Texas Red-LMD and comprise an intricate array of capillaries (small white arrows). <b>D</b> and <b>E</b>, Typical lymphangiogram at 15 minutes and 4 hours post-injection, in which images are partially-obscured by blotches of Texas Red-LMD (green arrows) that diffused from the original subcutaneous site. Scale bars, 50 µm.