Figure 6.

Melanin pigmentation and craniofacial phenotypes in reciprocal hybrids. A-C. Larval pigmentation. Dorsal views of surface fish x cavefish (SF X CF) hybrid (A) and cavefish x surface fish (CF X SF) hybrid (B) larvae at 10-days post-fertilization (dpf) showing cranial melanophores. Scale bar: 100 μm. C. Histograms showing the number of melanophores in the dorsal skin of surface fish (SF), SF X CF hybrids, and CF X SF hybrids. D-F. Juvenile pigmentation. Dorsal images of SF X CF (A) and CF X SF hybrids (B) at 30 dpf showing cranial melanophores. Scale bar: 50 μm. C. Histograms showing the number of melanophores in the dorsal skin of SF, SF X CF hybrids, and CF X SF hybrids. The regions in which melanophores were quantified are shown as boxes in A and D. The number of individuals is shown at the base of each histogram. A total of 75 hybrids from 3 reciprocal hybridizations were analyzed. Error bars: standard deviations of the means. ***denotes significance at < 0.001. ns: no significance. G-N. Craniofacial structure in juveniles at 30 dpf with cartilage stained blue and bone stained red. Lateral (G, I, K, M) and ventral (H, J, L, N) views of SF (G, H), SF X CF hybrids (I, J), CF X SF hybrids (K, L), and CF (M, N). Scale bar: 250 μm. Horizontal dotted lines show mandible spans. S: sclera. O-R. Sclera isolated from juveniles at 60 dpf. Frontal views of scleral cartilage rings dissected from SF (O), SF X CF hybrids (P), CF X SF hybrids (Q), and CF (R) of equivalent body lengths. Scale bar: 500 μm. S, T. Histograms comparing (S) the width of the lower jaw measured at the level of the hinge (dashed lines in J, L) and (T) the diameter of the sclera in SF X CF and CF X SF hybrids. The number of individuals is shown at the base of each histogram. A total of 46 hybrids from 2 reciprocal hybridizations were analyzed. Error bars: standard deviations of the means. ***denotes significance at < 0.001. ns: no significance.