Genetic and metabolic bases of two “albino” phenotypes in the leopard frog, Rana pipiens

Abstract

Preliminary characterizations of albino Rana pipiens from two widely separated geographic origins, Mexico and Michigan, indicated that different metabolic basÉs underlie the albino phenotype. Albinism in the Mexican frogs was shown to result from a single Mendelian recessive gene, am (amelanotic), and appeared to involve a biochemical failure of the pigment synthesizing system. Melanophores were present in am / am integument which exhibited tyrosinase activity when provided with exogenous tyrosine or L-DOPA. The tyrosinase activity of am / am melanophores showed greater thermolability than did that of wild type malanophores. The “albinism” of tadpoles collected in Michigan was only partial, and was associated with a highly pleiotropic syndrome, abnormal patterning of chromatophore distributions, and metamorphic failure. Poor pigmentation of integumental melanophores appeared associated in part with inhibitors of melanogenesis. Genetic data on the possible mode of inheritance are not yet available.