Sex Chromosome Meiotic Drive in Hybrid Males of the Common Shrew (Sorex araneus)

Patterns of sex chromosome segregation in six homozygous males of the common shrew (Sorex araneus LINNAEUS, 1758) belonging to two chromosomal races, as well as in 16 interracial hybrids were studied. Based on their karyotypes the hybrids can be subdivided into two groups: (a) complex heterozygotes, which form meiotic quadrivalents in chain and chain + ring configurations, and (b) complex heterozygotes, which form meiotic pentavalents in chain configurations. Random (1 : 1) segregation of sex chromosomes was found in homozygous as well as those heterozygous males which form meiotic complexes of four chromosomes. However, in some hybrids with meiotic pentavalents we observed a strong preferential segregation in favour of X chromosomes.