ISV sprout growth and patterning is disrupted by arsenic exposure and this disruption can be quantified from time-lapse images. A: At 24 hr post-fertilization, ISVs in the trunk region (adjacent to the yolk-plug extension) have begun sprouting bilaterally from the dorsal aorta at regular spatial and temporal intervals, with an anterior (left of image) to posterior (right of image) progression (green, flk-1 eGFP; red, tissue counterstain, rhodamine-lens culinaris agglutinin). B: Trunk ISVs in control and arsenic-treated zebrafish. Rostral ISV (left) in each panel is 5 hr post-initiation. Endpoint analysis of ISV growth shows that arsenic exposure results in altered ISV morphology, shorter thinner ISVs, missing ISVs, and more numerous filopodia. C: Using the Manual Tracking plugin in FIJI ImageJ, we tracked both ISV tip position and ISV base position for each ISV in 3D over time. Uncorrected tip positions over time (green) produce a trajectory that is the sum of the intrinsic ISV tip position and the local translocation of the embryo. Base positions over time (pink) produce a trajectory that defines the local translocation of the embryo. D: Using the angle measurement tool in FIJI ImageJ, we measured the angle between the proximal segment of the ISV and the DA segment anterior to each ISV. a, anterior; p, posterior. E: Arsenic-treated zebrafish are slightly shorter than age-matched controls but appear morphologically normal. F,G: Trunk regions of control and arsenic-treated zebrafish at 26 hpf show chevron-shaped myotomes by transmission imaging and by unc45 eGFP expression. ISVs, shown by kdr expression, in the arsenic treated ISVs are irregular in shape, length, and orientation as compared to control. DA, dorsal aorta; ISV, intersegmental vessel; m, myotome; n, notochord; PCV, posterior caudal vein. Panel A arrows identify ISVs. Panel A double arrow indicates location of notochord. Yellow line segments in panel D define the angle between the DA and ISV.