Wide-band agouti (aNb)
ALLELES: aNb (wide-band agouti), a+ (wild-type agouti), aw (white-belly non-agouti), a (non-agouti). The a allele was originally designated ae (See Robinson, 1981). Allelism of the series established by Dodson et al. (1987)
INHERITANCE: Complete dominance hierarchy: aNb > a+ > aw > a
PHENOTYPE: Wide-band agouti: Coat color is more yellow than the wild type of P.m. bairdii. The agouti bands of the individual hairs are lengthened relative to the total hair, and there is a corresponding reduction in the number of all-black guard hairs. The phenotype superficially resembles yellowing, which is a recessive trait, but usually can be distinguished by the greater number of dark guard hairs in wide band. The dorsal-ventral line of demarcation is not as distinct in wide band as in yellowing.
White-belly non-agouti: deer mice have a nearly black dorsal coat, white on underside, but base of hairs are black rather than gray. Feet are white. Overall aspect is "black and white". A few dark brown hairs occur at the base of the ears.
Non-agouti: Both dorsal and ventral pelage is predominantly black. There is no tail stripe, with all tail hairs being black. The forepaws are white, as are the toes of the hind foot. The short hairs on the surface of the pinnae are dark brown. The pre- and post-auricular tufts are silvery at the base. The longest vibrissae are black for at least their basal third, although many become lighter distally. A few small ventral white spots or hairs occur in some specimens.
LINKAGE: Linkage Group III (McIntosh, 1956a).
INTERACTIONS: None reported, but white-belly non-agouti and non-agouti probably are epistatic to yellowing.
SOURCES: The wide band allele has a high frequency in P.m. nebrascensis of the Nebraska sandhills, where the phenotype is typical of the subspecies. The wide-band variant was established from P.m. nebrascensis and maintained in laboratory stocks derived by repeated backcrossing to P.m. bairdii wild-type. Progeny, as expected, segregate 1:1.
The white-belly non-agouti allele was isolated from a single homozygous P.m. sonoriensis male trapped at the base of Little Granite Mountain in south-central Toole County UT.
The non-agouti allele was isolated from a wild-caught homozygous male P.m. gracilis collected in 1973 at the Hubbard Brook Experimental farm near West Thornton NH.
REFERENCES: Wide-band agouti: McIntosh (1956a); white-belly non-agouti: Egoscue (1971); non-agouti: Horner, et al. (1980), Robinson (1981).
COMMENTS: The white-belly non-agouti variant was initially reported as "non-agouti". The allelic name was changed when atypical non-agouti variant was subsequently discovered, since the latter was phenotypically more similar to non-agouti in other laboratory rodents.
Wide-band agouti was regarded for many years as a distinct locus, with the "wide-band" (Nb) allele dominant to the recessive wild-type "narrow band" (nb) allele. The locus was named for the recessive variant consistent with the practice in deer mouse genetics during the 1950s. Allelism with the a locus was established by Dodson et al. (1987), and the "Nb" was retained as the superscript for the dominant allele, and "narrow-band" is synonomous with the standard agouti wild-type (a+).