Some observations on high cavernous nostrils in the chicken

Wide high cavernous nostrils are characteristic of all chicken breeds of the V-shaped duplex comb type, whereas all other breeds have slit-type nostrils, including the Sicilian Buttercup breed that has the buttercup-type duplex comb. Crosses between the Sicilian Buttercup and La Flèche breeds and single comb breeds suggest that this trait is a pleiotropic effect of the Dv allele at the duplex locus and is inherited as a recessive when crosses are made to the wild type (d+). The buttercup allele (Dc) at this same locus does not influence nostril morphology by itself, but, when combined with the V-shape comb allele (Dv/Dc), it does allow a single Dv allele to produce mutant nostrils. In this case the inheritance appears dominant. It is proposed that cavernous nostrils are a pleiotropic effect of the comb-size-reducing ability of the Dv allele rather than its duplexing ability.