Figure 3. Size and shape comparison of wild type and gpc4^−/− neurocrania.

Locations of twenty lateral (A) and thirty-three ventral (B) skull landmarks used in the study. A complete description of each landmark is given in Table S1 (Supplementary Material). In both views, a wild type skull is shown. C, D) Linear regression of lateral (C) and ventral (D) skull centroid size vs. standard length for wild type (wt) and gpc4^−/− mutant zebrafish. gpc4^−/−neurocrania are significantly smaller than wild type neurocrania across a wide range of body sizes, as indicated by the significant downward shift in the gpc4^−/− regression line (p< 0.0001 for differences in intercept). E) Lateral and F) ventral views of a wild type (left column) and gpc4^−/−(right column) zebrafish skull. Center column: Deformation grid of neurocranial landmarks used in the study, derived from Procrustes superimposition of all wild type (n=12) and gpc4^−/− (n=12) specimens. The grid indicates how the configuration of landmarks (A, B) must be altered to “convert” a wild type skull (left) into a mutant skull (right). Perfectly square cells indicate no difference in mean shape between mutants and wild types; deviations from squares indicate the regions of local shape difference between the two groups.