Families Opisthorchiidae and Heterophyidae: Are they distinct?

Superfamily Opisthorchioidea Looss, 1899 consists of three well-known families, Opisthorchiidae, Heterophyidae, and Cryptogonimidae, with basic similarities in morphology and life-cycles. Many species in the first two of these families are human pathogens, such as Opisthorchis viverrini, O. felineus, Clonorchis sinensis, Haplorchis spp. and Metagonimus spp. Recently, a molecular phylogenetic study on the classification of Digenea revealed a paraphyletic relationship between Opisthorchiidae and Heterophyidae. For our study, we gathered and analyzed all available data in GenBank, together with new data of nuclear 18S ribosomal DNA and ribosomal internal transcribed spacer 2 (ITS2) sequences of the families within the Opisthorchioidea. Maximum likelihood and Bayesian inference analyses suggested that families Opisthorchiidae and Heterophyidae are inseparable from each other, with the former nested within the latter. Groupings in molecular trees are generally consistent with morphological features used in taxonomy.

Phylogenetic tree inferred from 18S rDNA sequences of Opisthorchioidea.Figure optionsDownload as PowerPoint slideHighlights
► Paraphyletic relationship between Opisthorchiidae and Heterophyidae.
► 18S rDNA and ITS2 sequences were used as DNA marker.
► ITS2 sequence is an inappropriate DNA marker for study phylogenetic relations of Opisthorchioidea.
► Grouping taxa by molecular data was consistent with morphological feature used in taxonomy.