Syntenic Relationship of Chromosomes in Species and Based on the Chromosome-level Genome Assemblies

The clade, to which the parasitic nematode genus belongs, contains taxa with diverse lifestyles, ranging from free-living to obligate vertebrate parasites. Reproductive strategies are also diverse in this group of nematodes, employing not only sexual reproduction but also parthenogenesis, making it an attractive group to study genome adaptation to specific conditions. An in-depth understanding of genome evolution, however, has been hampered by fragmented genome assemblies. In this study, we generated chromosome-level genome assemblies for two species and the outgroup species using long-read sequencing and high-throughput chromosome conformation capture (Hi-C). Our synteny analyses revealed a clearer picture of chromosome evolution in this group, suggesting that a functional sex chromosome has been maintained throughout the group. We further investigated sex chromosome dynamics in the lifecycle of and found that bivalent formation in oocytes appears to be important for male production in the mitotic parthenogenesis. This article is part of the Theo Murphy meeting issue ': omics to worm-free populations'.