Contracaecum rudolphii B: gene content, arrangement and composition of its complete mitochondrial genome compared with Anisakis simplex s.l

In the present study, we sequenced the complete mt genome (14,022 bp) of parasitic nematode Contracaecum rudolphii B and its structure and organization compared with Anisakis simplex s.l. The mt genome of C. rudolphii B is slightly longer than that of A. simplex s.l. (13,916 bp). C. rudolphii B mt genome is circular, and consists of 36 genes, including 12 genes for proteins, 2 genes for rRNA and 22 genes for tRNA. This genome contains a high A+T (70.5%) content. The mt gene order for C. rudolphii B is the same as those for A. simplex s.l., but it is distinctly different from other nematodes compared. The start codons inferred in the mt genome of C. rudolphii B are TTG and ATT. Six protein-coding genes use TAA as a stop codon whereas five genes use T and one genes use TAG as a termination codon. This pattern of codon usage reflects the strong bias for A and T in the mt genome of C. rudolphii B. Phylogenetic analyses using concatenated amino acid sequences of the 12 protein-coding genes, with three different computational algorithms (Bayes, ML and MP), all revealed distinct groups with high statistical support, indicating that C. rudolphii B and A. simplex s.l. is distinct but closely related species. These data provide additional novel mtDNA markers for studying the molecular epidemiology and population genetics of the C. rudolphii B, and should have implications for the molecular diagnosis, prevention and control of anisakidosis in humans and animals.