Conventional staining of male metaphase I (left panel) and female mitotic karyotypes (right panel). The sex-chromosome system types and the species names are shown directly in the figure. The sex chromosomes and chromosome arms of the neo-sex chromosomes involved in Rb-fusions are indicated. XL: arm derived from the original X chromosome fused to an autosome; XR: autosomal arm of the neo-X that shares homology with the neo-Y; YL: arm that shares homology with the XR arm; YR: arm that shares homology with the neo-X2 chromosome. Bar = 5 μm.