Genetic and experimental studies on a pigment mutation, Pale (P a), in the frog, Bombina orientalis

A mutant gene, Pale, (Pa) has been discovered in the discoglossid frog, Bombina orientalis. Breeding experiments indicate that the gene is recessive to the wild-type allele (P). Embryos, tadpoles and adults homozygous for the Pale gene are lighter in coloration than wild-type animals. Eggs produced by Pale females appear normally pigmented. Neural-retina defects were apparent in Pale tadpoles. Parabiosis experiments revealed that the Pale and wild-type phenotypes were unaffected by circulating factors from the opposite phenotype. Neuralcrest-grafting experiments revealed that Pale melanophores retain the Pale phenotype when placed in a wild-type cellular environment. Likewise, wild-type chromatophores are unaffected by residence in Pale tissues. Melanophores of Pale tadpoles display reduced numbers of mature melanosomes. This is the primary morphological basis of the Pale phenotype. However, other chromatophore classes (xanthophores, iridophores) were also less intensely pigmented, demonstrating that a single gene may affect the pigmentation of all chromatophore classes in B. orientalis.