A karyotypic comparison between the blue fox and the silver fox revealed conservation of the chromosome arm as a unit, except for large heterochromatic blocks in 10 pairs of blue fox chromosomes and the complete absence of a common metacentric autosomal pair. This finding seems to indicate that their karyotypes evolved from a common ancestral karyotype, characterized by 70–76 acrocentric autosomes, mainly through a series of independent centric fusion