Genetics of color mutations in the snake, Elaphe obsoleta

Abstract

The following snakes were located and acquired: two albino black rat snakes; one xanthic black rat snake, one hypopigmented black rat snake with phenotype not previously described; one leucistic Texas rat snake, one F1 wild-type black rat snake heterozygous for albinism, and one male and two female F1 wild-type Texas rat snakes heterozygous for albinism. Between 1975 and 1983 these snakes were subjected to various breeding combinations to determine their genetics. The results of 29 matings are summarized. All of the aberrant phenotypes were found to be autosomal recessive mutations. Allelic and nonallelic forms of albinism were found to exist in the black rat snake. The xanthic form of hypopigmentation was found to be tyrosinase—positive partial albinism. Leucism in the Texas rat snake appears to be associated with bilateral exophthalmos in some instances. The previously undescribed black rat snake phenotype was designated “brindle” because of its appearance. It appears to be a genetically determined alteration in the quantity or quality of pigment, or both, and it does not undergo ontogenetic loss of pattern. It is not a form of tyrosinase-positive albinism analogous to the xanthic phenotype.