Morphological And Molecular Taxonomic Studies Of Nine Species Of Myxosporeans (Myxozoa: Myxosporea) Parasitic In Fresh Water Fishes

The present survey presents the descriptions of these nine myxosporeans, which are studied with the guidelines of Lom & Arthur and Lom & Dyková, while the taxonomy system and experimental ways followed the compendious classified system and research methods presented by Zhao & Song. Phylogenetic trees were conducted by neighbor-joining and maximum parsimonyanalyses method of the 18S rDNA sequences of myxosporeans in PAUP 4.0b10.In recent years, some surveys of freshwater fish parasites have been carried out in upper zone of Yangtze River, China. In this study, nine species of myxosporeans, Myxidium huidongense Ma et Zhao, Myxidium cuneiform Fujita, Thelohanellus nikolski Achmerov, Myxobolus hearti Chen, Myxobolus hypophthalmichthydis (Dogiel et Achmerov), Myxobolus mai sp. n., Myxobolus sp., Unicauda pelteobagrus Ma, Chloromyxum ellipticum Li et Nie, from the different fresh waters fishes, were investigated during 2008-2009. By using the method of the morphologic taxonomy and molecular taxonomy, morphologic informations and 18S rDNA sequence data of the four Myxosporeans have been descripted and suppliedAccording to the morphologic features of the spores and phylogenic analysis inferred from 18S rRNA genes for these myxosporeans, the results show that evolutionary approach of Myxidium is manifested to be polyphyletic evolution, species of the genera Myxidium and Zschokkella occur in basal clades, and these myxosporeans evolved into species of similar spore type; that T. nikolskii and T. dogieli were different from each other in the shape, and these two species are valid species, respectively, T. nikolskii is the first record in Chongqing; that genus Unicauda was also testified to be valid and to be the closely genetic relationship with genus Henneguya based on molecular data; and that the phylogenetic trees of Myxobolus and Chloromyxum showed the two genera were complicated and nonmonophyletic group for taxonomic status. In estimating myxozoan phylogeny, it is unclear which morphological characters are most useful for classification of these parasites in a taxonomic scheme that reflects their evolutionary history and is supported by molecular data.