Chromosome-level Genome of the Muskrat (Ondatra zibethicus)

The muskrat (Ondatra zibethicus) is a semi-aquatic rodent species with ecological, economic, and medicinal importance. Here, we present an improved genome assembly, which is the first high-quality chromosome-level genome of the muskrat with high completeness and contiguity assembled using single-tube long fragment read, BGISEQ, and Hi-C sequencing technologies. The genome size of the final assembly was 2.63 Gb with 27 pseudochromosomes. The length of scaffold N50 reached 80.25 Mb with a Benchmarking Universal Single-Copy Ortholog score of 91.3%. We identified a 66.98 Mb X chromosome and a 1.14-Mb Y-linked genome region, and these sex-linked regions were validated by resequencing 32 extra male individuals. We predicted 19,396 protein-coding genes, among which 19,395 (99.99%) were functionally annotated. The expanded gene families in the muskrat genome were found to be enriched in several organic synthesis- and metabolism-related Gene Ontology terms, suggesting the likely genomic basis for the production and secretion of musk. This chromosome-level genome represents a valuable resource for improving our understanding of muskrat ecology and musk secretion.