Genetic analysis of VAB, SN and eye regression. (A-E) Histograms showing (A) VAB level (square-rooted number of approaches, or NOA), (B) SO-3 SN number, (C) EO SN number, (D) SO-3 SN diameter, and (E) eye diameter in surface fish, cavefish and their F1 progeny (upper frames), and the F2 and F3 generations (lower frames). The F1 and F2 phenotypes are intermediate between surface fish and cavefish, and the sum of F2 and F3 phenotypes covered most of the range of phenotypes for each trait between surface fish and cavefish, although the distributions of SO-3 and EO SN numbers remain somewhat restricted towards the surface fish phenotype. (F-G) Regression analysis showing the relationships between VAB and (F) EO SN number, (G) SO-3 SN number, (H) SO-3 SN diameter, and (I) eye diameter/SL. (J) The relationship of SN number at EO and eye diameter/SL. EO SN number and SO-3 SN diameter were both positively correlated with VAB level, which was negatively correlated with eye size. EO SN number was also negatively correlated with eye size. Linear regression lines are shown in red. (K-N) Bright field images (upper) and DASPEI-stained neuromasts (lower) compared among (K) surface fish, (L-M) two examples of F3 hybrids, and (N) cavefish. Scale bar in (N) is equal to 1.0 mm. In K-N, circles outlined by white dashed lines indicate the edges of the eye, red dashed lines indicate the lines of suborbital canal neuromasts in the head lateral line, the areas enclosed by the blue dotted lines indicate the approximate outline of the SO-3 region, and the areas shown by the yellow dotted lines and indicated by yellow arrows show the EO regions.