crs blood cells produce excess ROS and undergo oxidative stress. (A-B) Live wild-type (A) and mutant (B) embryos incubated with dihydrorhodamine 123 at 36 to 38 hpf. (C-D) Whole-mount in situ hybridization for heme oxygenase-1 (ho-1) at 36 to 38 hpf in wild-type (C) and mutant (D) embryos. A single cell in the tail vessels of the wild-type embryos is marked by an arrow in panel C. The region bracketed in panel D is shown at higher magnification (inset) with a ho-1⁺ cell (arrow) next to an unlabeled cell (arrowhead) in the caudal artery (CA).