Fig. 7. Epistasis analysis of brain ventricle mutants snk and nok. (A-H) Lateral and dorsal views of anesthetized, living embryos at 25 hpf. (A,E) Wild type (70/139 embryos, 50%); (B,F) nagie oko mutants (29/139 embryos, 21%); (C,G) snakehead mutants (30/139 embryos, 22%). (D,H) snakehead;nagie oko double mutants (10/139, 7%) show overall composite phenotype. Asterisks mark hinge-points, which are visible in wild type but not visible in the mutants (although hinge-points are present in the snk mutant; see K). Arrow marks midbrain-hindbrain constriction, which is visible in wild type and nok mutant but is not visible in snk nor snk;nok due to the altered refractivity of the snk tissue. (I-L) Histological sections through midbrain at 22 hpf of wild type (I), nok (J), snk (K) and snk;nok (L). The phenotype appears to be additive, suggesting nagie oko and snakehead function in separate pathways. (M-P) Drawings of brain outline and ventricle lumen in I-L show composite phenotype more clearly. Scale bar: 50 µm. H, hindbrain ventricle; M, midbrain ventricle.