Figure 4. Mc1r genotype-phenotype correlation in representative members of an F₂ pedigree derived from a Surface×Pachón cavefish cross.

(A,D,G,J) We crossed two F₁ hybrid individuals to generate a small pedigree of individuals demonstrating a range of pigmentation phenotypes. (A) Each fish was photographed from the right side to visualize the entire head or a region just posterior to the orbit of the eye (red rectangle). Each individual was also genotyped for the polymorphic region of Mc1r ORF housing the fixed 2-bp deletion found in members of the Pachón cave. (C,F,I,L) The resulting chromatogram sequence data is depicted to the right of each individual image. (A–C) We found that the darkest individual, with the most melanophores, carries two copies of the Surface form of Mc1r. (D–F) The heterozygous individual demonstrates roughly the same number of melanophores, however each cell appears to produce less eumelanin. (G–I) A non-albino F₂ individual with two copies of the Pachón allele of Mc1r demonstrates the least amount of pigmentation compare to other pigmented genotypes, however this individual clearly differs from (J) albino phenotypes. (J–L) An albino individual carrying two mutant copies of the gene Oca2 [1] who carries two Surface copies of Mc1r cannot produce pigment, demonstrating the epistatic nature of the albino mutation. Scale bars: A,D,G,J = 3 mm; B,E,H,K = 500 µm.