Fig. 7. Ventricular morphology responds to atrial dysfunction in wea mutants. (A-D) Longitudinal sections through the heart at 72 hpf, stained with Hematoxylin and Eosin, anterior to the top. (A,B) Sections through the wild-type (A, arrow) and wea mutant atrium (B, arrow) demonstrate similar thickness of the atrial wall. The wea mutant atrium is dilated in comparison with the wild-type atrium and contains less blood. (C,D) Comparison of sections through the wild-type (C, arrow) and wea mutant ventricle (D, arrow) demonstrates that the ventricular wall is thicker, and that the ventricular lumen is narrower, in wea mutants. The morphology of the wea mutant ventricle varies between individuals (D); insets show two additional examples of ventricular sections from other wea mutant embryos. Variability is also apparent within individual embryos, as the wea mutant ventricular wall does not exhibit a uniform thickness. (D) Thickening of the wea mutant ventricular wall is apparent by 48 hpf, and increases between 48 and 72 hpf (data not shown). All sections shown are the central section from serial sectioning through the respective chamber; results are representative of the examination of more than 15 embryos of each genotype.