Sex chromosome composite idiogram of probe localization by FISH. Centromeres are represented as small, constricted blocks, and nucleolous orgranizer regions, often found proximal to the centromere, are represented by three thin lines. Chromosomal location of hybridization is indicated in black. Each image was made from observations of ten metaphase spreads. The relative sizing of X chromosomes is according to  and this study. Vertical lines separate relative groups of species based on probe distribution in the X and Y. Predominant centromeric probes (pc) indicate hybridization of probe to all autosomal centromeres of the species.