Sex chromosome abnormalities in natural populations of the common vole (Microtus arvalis)

Four specimens with an aberrant sex chromosome constitution were found in natural populations of the common vole (Microtus arvalis). Two females had an XO sex chromosome constitution and single males were 2n = 47, XXY and 2n = 47, XYY, respectively. No apparent phenotypical anomalies were recorded in the sex chromosome aneuploids, but their fertility may have been impaired. The incidence of sex chromosome aneuploidy seems to be unusually high in natural populations of the common vole (1.5 % of animals examined). Possible explanations for this are discussed.