ABNORMALITIES OF THE FEMALE GENITAL ORGANS IN MINK HETEROZYGOUS FOR THE HEGGEDAL FACTOR (SHADOW FACTOR).

In Sapphire Shadow (aa pp SHs), Blue Shadow (AA pp SHs) and Blue Shadow Carrier for Aleutian (Aa pp SHs) a malformation of the female genital organs has been demonstrated and described. The malformations seem to be restricted to the areas which are formed by the Müllerian ducts and chiefly affect the vagina and cervix, corpus and cornua uteri, whilst the uterine tubes are as a rule normal. Among females which are empty after their first breeding season the frequency of these malformations was almost 42 % and among virginal young females 18.5 %. The abnormalities seem to be due to a pleiotropic, possibly sexlimited effect of the Heggedal factor (Shadow factor SH). With respect to these malformations, the Heggedal factor acts as a dominant hereditary factor with incomplete penetrance and varying expressivity. The penetrance in the females was approximately 18.5 % (18.54 ±2.71). A method for demonstrating the malformations in live mink is described.