Mitochondrial genome of Hypoderaeum conoideum – comparison with selected trematodes

BACKGROUND: Hypoderaeum conoideum is a neglected but important trematode. The life cycle of this parasite is complex: snails serve as the first intermediate hosts: bivalves, fishes or tadpoles serve as the second intermediate hosts, and poultry (such as chickens and ducks) act as definitive hosts. In recent years, H. conoideum has caused significant economic losses to the poultry industry in some Asian countries. Despite its importance, little is known about the molecular ecology and population genetics of this parasite. Knowledge of mitochondrial (mt) genome of H. conoideum can provide a foundation for phylogenetic studies as well as epidemiological investigations. METHODS: The entire mt genome of H. conoideum was amplified in five overlapping fragments by PCR and sequenced, annotated and compared with mt genomes of selected trematodes. A phylogenetic analysis of concatenated mt amino acid sequence data for H. conoideum, eight other digeneans (Clonorchis sinensis, Fasciola gigantica, F. hepatica, Opisthorchis felineus, Schistosoma haematobium, S. japonicum, S. mekongi and S. spindale) and one tapeworm (Taenia solium; outgroup) was conducted to assess their relationships. RESULTS: The complete mt genome of H. conoideum is 14,180 bp in length, and contains 12 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and one non-coding region (NCR). The gene arrangement is the same as in Fasciola spp, with all genes being transcribed in the same direction. The phylogenetic analysis showed that H. conoideum had a relatively close relationship with F. hepatica and other members of the Fasciolidae, followed by the Opisthorchiidae, and then the Schistosomatidae. CONCLUSIONS: The mt genome of H. conoideum should be useful as a resource for comparative mt genomic studies of trematodes and for DNA markers for systematic, population genetic and epidemiological studies of H. conoideum and congeners.