Cytogenetic Analysis of the Members of the Snake Genera , , , and

The recent discovery of two independently evolved XX/XY sex determination systems in the snake genera and sparked a new drive to study the evolution of sex chromosomes in poorly studied lineages of snakes, where female heterogamety was previously assumed. Therefore, we examined seven species from the genera , , , and by conventional and molecular cytogenetic methods. Despite the fact that these species have similar karyotypes in terms of chromosome number and morphology, we detected variability in the distribution of heterochromatin, telomeric repeats, and rDNA loci. Heterochromatic blocks were mainly detected in the centromeric regions in all species, although accumulations were detected in pericentromeric and telomeric regions in a few macrochromosomes in several of the studied species. All species show the expected topology of telomeric repeats at the edge of all chromosomes, with the exception of , where additional accumulations were detected in the centromeres of three pairs of macrochromosomes. The rDNA loci accumulate in one pair of microchromosomes in all species and in , in one macrochromosome pair in and in two pairs of microchromosomes in . Sex-specific differences were not detected, suggesting that these species likely have homomorphic, poorly differentiated sex chromosomes.