Phylogeny of zoonotic parasites in fresh and blackish water fish in Vietnam

Trematode metacercariae were examined from 5 fish species (striped catfish Pangasianodon hypophthamus, climbing perch Anabas testudineus, goldfish Carassus auratus, greater lizardfish Saurida tumbil,  and mullet Mugil cephalus  by morphological and genetic characters.  A total of 14 trematode species were found, of which 5 species (Clonorchis sinensis, Centrocestus formosanus, Haplorchis yokogawai, H. taichui and  Bucephalus sp. ) were in striped catfish, 5 unidentified species (Centrocestus sp., Haplorchis sp., Metagonimoides sp. Heterophyidae sp1., and Heterophyidae sp2.) in climbing perch, Haplorchis taichui in Carassus auratus, 1 unidentified species Tormopsolus sp. in Saurida tumbil, and 3 unidentified species (Procerovum sp., Stellachasmus sp., Clonorchis sp.) in Mugil cephalus. Sequence differences of species ranged from 2.3% to 10.6% of 28S rDNA and from 1.5% to 35.7% of ITS1 rDNA. A phylogenetic tree was constructed based on 28S and ITS1 genes of ribosomal DNA using Maximum Parsimony, Maximum Likelihood and Bayesian Inference algorithms. The 28S rDNA phylogram showed the monophyly of studied metacerarian genera, except Haplorchis and Procevorum. Species of Opisthochidae (Clornochis spp.) were placed in the same clade as those from Heterophyidae. 2 unidentified species (Heterophylidae sp1. and Heterophyidae sp2.) showed close relationship with Haplochis and Procevorum species. The ITS1 phylogenetic tree resulted in the same unclear branching for  Haplorchis and Procevorum. Bucephalus sp. (Bucephalidae) was clearly distinguished from all Heterophyidae species. Morphological and phylogenetic analyses are necessary for species identification and taxonomic positions of unidentified species.