Male and female genomes of millipede (Trigoniulus corallinus) and identification of sex chromosomes

Arthropods are arguably the most successful group of metazoans, comprising the majority of described animal species. Millipedes belong to the class Diplopoda of arthropods and are vital decomposers of litter and recycle nutrients in the soil ecosystems worldwide. The molecular mechanism of sex determination in millipedes remains unknown. Here, we sequenced and assembled two high-quality genomes of male and female rusty millipedes <i>Trigoniulus corallinus</i> with sizes of 546 Mb (scaffold N50 = 21.9 Mb) and 630 Mb (scaffold N50 = 20.7 Mb), respectively. Whole-genome resequencing was further carried out on 10 males and 10 females, and sequencing depth analyses showed 1 X chromosome and 2 X chromosomes on male and female genome assemblies, suggesting an XX/X0 system. Synteny analyses of <i>T. corallinus</i> with the centipede <i>Strigamia acuminata</i> showed little conservation between their X chromosomes, implying different selection pressures happened on sex chromosomes after their divergence from the myriapod ancestor. The survey of the sex chromosomes of a millipede species provides the first genomic evidence supporting an XX/X0 system in millipedes. It provides a foundational framework for future studies in myriapod genomics and contributes to a broader understanding of arthropod evolution.