Characterization of the Complete Mitochondrial Genome Sequence of Contracaecum sp. (Nematoda: Ascarididae) from China

Contracaecum spp. is a zooparasitic anisakid nematode and occurs in gastrointestinal tracts of vertebrate/invertebrate animals, humans included, causing gastrointestinal pain, diarrhea, and increasingly severe vomiting. To date, thousands of sequences have been published in GenBank, while complete mitochondrial genomes (mitogenome) of Contracaecum spp. are still limited. Although the complete mitogenome of Contracaecum species isolated from night herons in Beijing has been reported, the detailed information about it is still puzzling. In the present study, we describe the detailed characteristics within the complete mt DNA Contracaecum sp.. The AT-content in the complete mitogenome of Contracaecum sp. was 72.2%. The nucleotide diversity (Pi) among genus Contracaecum ranged from 0.124 ( cox 1) to 0.181 ( nad 4). Based on the computational algorithms Maximum Likelihood (ML) and Bayesian Inference (BI) within Ascaridoidea and Heterakoidea, the results supported Contracacum sp. Beijing isolate was a new species in the genus Contracaecum , and supported the family Ascaridiidae was paraphyletic.