show Abstracthide AbstractThe Okinawa island spiny rat, Tokudaia muenninki, has highly unique sex chromosomes. The diploid chromosome number of T. muenninki is 44 with XX/XY sex chromosome constitution, and both sex chromosomes are uncommonly large. The euchromatic regions of the X and Y chromosomes occupy 8% and 4% of the haploid genome, indicating that autosomal fusions have occurred. T. muenninki has multiple SRY copies on the large Y chromosome. Therefore, we conducted whole genome sequencing and de novo assembly analysis for two aims: first, to utilize the information for the research of the evolution of the sex chromosomes, and second, to reserve the information as an important resource.