Phylogenomics and the evolutionary history of the Oxyurida (pinworms).

Pinworms (Nematoda: Oxyurida) are among the first documented zooparasitic nematodes, and some species are of veterinary, medical, and economic importance. However, the basic molecular phylogenetic framework for the Oxyurida is far from comprehensive, and the origin and early evolutionary history of the group remain little understood. In this study, phylogenomic analyses of the Oxyurida, involving the most comprehensive family-level taxon sampling of pinworms to date, were performed based on the universal single-copy orthologues and the mitochondrial protein-coding genes. Phylogenomic results yielded a highly resolved tree that confirmed the validity of the family Gyrinicolidae, suggested that the Heteroxynematidae is nested within the Oxyuridae and should be treated as a subfamily within the latter family (Heteroxynematinae status novus), and failed to support the separation of the subfamilies Oxyurinae and Syphaciinae. Using fossil-based time priors to calibrate both mitogenomic and genomic phylogenies, we establish the first comprehensive evolutionary timescale for pinworms. Our results place the most recent common ancestor of the Oxyurida in the late Devonian and further support the hypothesis that members of the vertebrate-parasitic Oxyuroidea initially parasitized reptiles and later extended their host range to mammals, and during this transition, opportunistically produced a highly specialized lineage infecting anuran tadpoles.