A. Time-lapse confocal microscopy of representative Tg(kdrl:EGFP) rab13+/+ and rab13∆3'UTR /∆3'UTR embryos. DLAV: dorsal longitudinal anastomotic vessel; HM: horizontal myoseptum. T0= 25 hpf; arrowheads indicate extra branches emerging from the main ISVs at the HM position; scale bars = 50 µm (A). 