SYNONYM: Naked (nk). ALLELES: hr-2+ (wild-type), hr-2 (mutant).
INHERITANCE: Recessive, heterozygotes recognizable.
PHENOTYPE: Homozygous adults are virtually nude except for vibrissae and sensitive hairs which exist as short stumps. Some individuals have normal shaped, but short vibrissae. The trait can be detected in newborn deer mice by the twisted appearance of the vibrissae. Animals begin to lose hair about twelve days of age, following a period during which the coat has a distinctive sheen. Juveniles have dark pigmented bodies with pink faces. Transient coats appear at subadult and adult molts. The deer mice are most readily distinguished from hairless-1 by the absence of elongate claws. Scanning electromicroscopy reveals many hairs that are abnormally twisted or bilobar, and that are fragile and readily break off at the skin surface. Ears of homozygous hairless-2 deer mice are abnormally thin and there is a general reduction in body weight.
Heterozygous hairless-2 deer mice have full pelage, but the coat has a greasy texture.
INTERACTION: Crosses between homozygous hairless-1 and hairless-2 deer mice have full pelage, except for the oily coat of the heterozygous hairless-2. SOURCE: About 1960. University of Utah Dugway Ecological Laboratory. Two male offspring from a wild-caught female P.m. sonoriensis showed the trait.
REFERENCE: Egoscue (1962), Knapp and Dawson (?1992).