J. L. Fierst, L. Arbex Herden, V. K. Eggers, C. A. Burns, J. A. Sosa, P. Kayastha, M. A. McCauley, K. Willicott
Sex chromosomes are deeply conserved in some organisms but remarkably labile in others. Here we describe a novel, female-hemizygous ZW sex chromosome system in the nematode Bunonema JU3390. We propose this neo-sex chromosome evolved from an autosome to escape mutational meltdown from lethal structural mutations accumulated during a period of parthenogenesis, demonstrating the role of evolutionary contingency in this rapid re-invention of sex.