biostudies-literatureHarbin JPAmerican Cancer SocietyNIHNIGMS NIH HHSNIH HHSiyae207https://www.ebi.ac.uk/biostudies/studies/S-EPMC12005254biostudies-literatureUnknown229(4)Sexual characteristics and reproductive systems are dynamic traits in many taxa, but the developmental modifications that allow change and innovation are largely unknown. A leading model for this process is the evolution of self-fertile hermaphrodites from male/female ancestors. However, these studies require direct analysis of sex determination in male/female species, as well as in the hermaphroditic species that are related to them. In Caenorhabditis nematodes, this has only become possible recently, with the discovery of new species. Here, we use gene editing to characterize major sex determination genes in Caenorhabditis nigoni, a sister to the widely studied hermaphroditic species Caenorhabditis briggsae. These 2 species are close enough to mate and form partially fertile hybrids. FirGeneticsRobust sex determination in the Caenorhabditis nigoni germ line.PMC12005254R01GM118836R01 GM118836R01 GM121688R01GM121688P40 OD010440126627-PF-15-228-01-DDCKemper KHaag ESHarbin JPSchwarz EMShen YEllis RELin SYfalseRobust sex determination in the Caenorhabditis nigoni germ line.Sexual characteristics and reproductive systems are dynamic traits in many taxa, but the developmental modifications that allow change and innovation are largely unknown. A leading model for this process is the evolution of self-fertile hermaphrodites from male/female ancestors. However, these studies require direct analysis of sex determination in male/female species, as well as in the hermaphroditic species that are related to them. In Caenorhabditis nematodes, this has only become possible recently, with the discovery of new species. Here, we use gene editing to characterize major sex determination genes in Caenorhabditis nigoni, a sister to the widely studied hermaphroditic species Caenorhabditis briggsae. These 2 species are close enough to mate and form partially fertile hybrids. Fir2025-01-01T00:00:00Z2025 Apr2026-07-01T03:24:41.247Z2025-06-28T03:05:29.359ZS-EPMC120052543966384910.1093/genetics/iyae207