crs red blood cells fail to differentiate and are reduced in number. (A-D) Hematoxylin and eosin staining of blood cells from whole-mount wild-type (A,C) and mutant (B,D) embryos at 33 hpf (A-B) and 48 hpf (C-D). Binucleated cells were often observed (B, arrows). (E-F) Wright-Giemsa staining of isolated blood cells from wild-type (E) and mutant (F) embryos at 36 hpf. (G-H) Bright-field microscopy of blood cells in wild-type (G) and mutant (H) embryos at 42 hpf in the caudal artery with spaces between the reduced cell numbers in mutant animals bracketed (H).