Mutations in hmgcs1 cause a decrease in hemoglobinized RBCs. (A-B) hmgcs1^−/− (Vu57) and their wild-type siblings (hmgcs1^+/+) were stained for hemoglobinized RBCs at 4 dpf (n = 36 hmgcs1^+/+, n = 29 hmgcs1^−/−) using o-dianisidine. Ventral views (A-B) of the hemoglobinized RBCs are shown with full body images (A′-B′) of both wild-type siblings and homozygous mutants (Vu57). The phenotype was completely penetrant in homozygous mutants. Total numbers of animals were obtained across a minimum 3 biological replicates. Images were taken with a 10× optical lens at 8× (A-B) and 6.3× (A′-B′) objective zoom. (C) The concentration of hemoglobin was measured in siblings (a pool of wild-type and heterozygous individuals) and embryos carrying the Vu57 allele. The assay was performed with 2 biological replicates with a total of 60 larvae. *P < .05.