Allelic variation and duplication of the dmrt1 were associated with sex chromosome turnover in three representative Scatophagidae fish species

Fish species of the family Scatophagidae possessing known candidate sex-determining genes (male-specific dmrt1Ys), offer suitable models for studying sex chromosome evolution. Here, we analyzed sex chromosome turnover events in three representative fish species of the family Scatophagidae, belonging to the genera Scatophagus and Selenotoca, which diverged 12.8 million years ago (Mya). Prior to the divergence of Sc. argus and Sc. tetracanthus 7.2 Mya, their dmrt1Y was differentiated from its locus, the truncated dmrt1ΔX, through allelic variation. The Y chromosome (Chr1) of Sc. tetracanthus is the result of the fusion of the original Y chromosome (Chr4) with an autosome (Chr13). The Se. multifasciata dmrt1Y arose from a duplication of dmrt1 on Chr4 and then translocated to the new Y chromosome (Chr18). The divergent evolutionary trajectories of the dmrt1Ys were accompanied by sex chromosome turnover in these three species. The sex chromosomes of the Scatophagidae family have evolved rapidly, albeit not randomly. The integration of genome sequencing, genome re-sequencing, QTL mapping and gonadal transcriptome data reveals that the sex chromosome has undergone rapid turnover in three closely related species of the family Scatophagidae.