Oesophagostomum dentatum and Oesophagostomum quadrispinulatum: Characterization of the complete mitochondrial genome sequences of the two pig nodule worms

In the present study, the complete mitochondrial DNA (mtDNA) sequences of the pig nodule worm Oesophagostomum quadrispinulatum were determined for the first time, and the mt genome of Oesophagostomum dentatum from China was also sequenced for comparative analysis of their gene contents and genome organizations. The mtDNA sequences of O. dentatum China isolate and O. quadrispinulatum were 13,752 and 13,681 bp in size, respectively. Each of the two mt genomes comprises 36 genes, including 12 protein-coding genes, two ribosomal RNA and 22 transfer RNA genes, but lacks the ATP synthetase subunit 8 gene. All genes are transcribed in the same direction and have a nucleotide composition high in A and T. The contents of A + T are 75.79% and 77.52% for the mt genomes of O. dentatum and O. quadrispinulatum, respectively. Phylogenetic analyses using concatenated amino acid sequences of the 12 protein-coding genes, with three different computational algorithms (maximum likelihood, maximum parsimony and Bayesian inference), all revealed that O. dentatum and O. quadrispinulatum represent distinct but closely-related species. These data provide novel and useful markers for studying the systematics, population genetics and molecular diagnosis of the two pig nodule worms.

Graphical abstractDownload full-size imageHighlights► The complete mt genome of the pig nodule worm Oesophagostomum quadrispinulatum was determined the first time. ► Its mtDNA sequence was analyzed and compared with that of Oesophagostomum dentatum China and Denmark isolates. ► Phylogenetic analyses revealed that O. dentatum and O. quadrispinulatum were closely related. ► mtDNA sequences provide novel markers for studying the population genetics of Oesophagostomum.