Albinism in the Snake, Elaphe obsoleta

Abstract

Four albino black rat snakes, Elaphe obsoleta obsoleta, one tan or xanthic in color and the other three completely amelanistic, were subjected to various breeding combinations to determine their genetic relationships. They were found to represent three distinct forms of albinism. Skin biopsies from the three forms were subjected to the dopa reaction, and biopsies from two of the forms were examined by frozen section. The two amelanistic forms were found to be non-allelic and to have biochemically different types of albinism, one tyrosinase-positive and the other tyrosinase-negative. The hypomelanistic or xanthic albino form was found to be tyrosinase- positive, allelic with the amelanistic tyrosinase-positive form, differing quantitatively in the bio- chemical defect in melanogenesis. The occurrence of albinism in Elaphe obsoleta is documented. Hensley (1959) surveyed the known records of albinism in North American reptiles and amphibians, and listed 12 records for the species. This list included many that had been reported in scattered references plus some that had not been recorded previously. Two of the records were from Texas and presumably were of the subspecies lindheimeri, but the remaining 10 were from within the range of the nominate form. No similar survey has been published since 1959. However, albinism is a regular though uncommon mutation that has been found in every vertebrate form of which a sufficient number of individuals have been observed, and sporadic albino specimens continue to be found as more individual snakes are collected. The common name of Elaphe obsoleta obsoleta is black rat snake. However, the individual snakes are by no means always uniformly black, with differences not only in different parts of the range but also individual differences within various parts of the range. The dorsal scales are generally black, but the skin between many of the scales is often of a much lighter color: white, yellow, orange, or red (Conant, 1958). There are frequently lighter shades at the edges of many of the scales. This, in combination with the lighter shades between some of the scales, results in considerable variation in the appearance of individual snakes. The chief variation is the persistent visible trace of the juvenile pattern still present in many adult snakes. This may be visible at all times, but is especially noticeable if the scales are distended for any reason, such as the recent ingestion of a large meal. The juveniles are strongly patterned dorsally with dark blotches on a pale gray background. They darken rapidly with age and some, most, or virtually all of the juvenile pattern is gradually obscured by black. Individual adult albinos of this species also are not necessarily identical. A typical one (PI. 1) has a yellow-tinged white background with dorsal blotches that are generally some shade of yellow, tan, peach, or red. The blotches may be barely discernible as a light pink or tan, they may be quite conspicuous, or may be absent, resulting in an essentially white snake. The eyes have a gold or pink iris with a red pupil, and the tongue is also red. Preserved specimens do not give an accurate