Molecular Phylogeny Of The Subfamily Diplozoinae And Aspidogaster Spp. Distributed In China

Diplozoids in the subfamily Diplozoinae (Monogenea, Mazocraeidea, Diplozoidae) are common parasites on gills of mainly freshwater cyprinid fishes. The subfamily contains 5 genera, i.e. Diplozoon Nordmann, 1832, Paradiplozoon Achmerov, 1974, Inustiatus Khotenovsky, 1978, Sinidiplozoon Khotenovsky, 1981, and Eudiplozoon Khotenovsky, 1984. The Aspidogaster (Trematoda, Aspidogastrea, Aspidogastridae) is the most archaic group among the platyhelminths, parasitizing molluscs, bony fishes and freshwater turtles. In the present study, the phylogenetic relationships of 29 samples representing 5 genera within the Diplozoinae and 10 species of the Aspidogaster were studied.The phylogenetic relationship of five genera, i.e. Diplozoon Nordmann, 1832, Paradiplozoon Achmerov, 1974, Inustiatus Khotenovsky, 1978, Sindiplozoon Khotenovsky, 1981, and Eudiplozoon Khotenovsky, 1985 in the subfamily Diplozoinae Palombi, 1949 (Monogenea, Oligonchoinea) was examined by analyzing ITS-2 rDNA sequences with neighbor-joining (NJ), maximum likelihood (ML) and Bayesian methods. The phylogenetic trees produced by using NJ, ML and Bayesian methods exhibit essentially the same topology. Surprisingly, parasites in Paradiplozoon on freshwater fish from Europe were clustered together with parasites in Diplozoon, but separately from species in Paradiplozoon on freshwater fish in China. The cluster of Paradiplozoon in Europe with the Diplozoon and the lower level of divergence (4.1%-15.7%) in ITS-2 rDNA sequences between the Paradiplozoon in Europe and Diplozoon, and the higher level of divergence (45.3%-53.7%) between the Paradiplozoon in Europe and in China may suggest that the generic status of diplozoids in Paradiplozoon in Europe needs to be revised. Thus, Diplozoon and Sindiplozoon form a large well-supported clade, which, together with Eudiplozoon, appears to be the sister of Inustiatus. Paradiplozoon forms the most basal clade in the Diplozoinae. The lower level of divergence (<1.0%) in ITS-2 rDNA sequences for diplozoids in the Paradiplozoon in China may also indicate the need for morphological re-examination, and so in the Inustiatus.The molecular variation of 10 species of the Aspidogaster from different geographical regions and different hosts from China were examined by comparing necleotide sequences of ITS rDNA. A. chongqingensis should be a synomym A. limacoides. Phylogenetic analyses revealed that the Aspidogaster species formed three main branches with high supports, respectively representing A. ijimai, A. conchicola and A. limacoides. There was a close relationship between A. ijimai and A. limacoides, which...