Phylogenic Analyses Inferred From The Representative Species Of Three Importaint Genera Of Myxosporeans

Phylogenic analyses inferred from the three representative species of myxosporeans, Myxobolus ampullicapsulatus, Unicauda pelteobagrs and Henneguya zikawiensis, were finished in the present work. Firstly, sequence similarity and mutation site, genetic diversity and molecular phylogeny based on SSU rDNA sequence, ITS-5.8S rDNA sequences and 28S rDNA sequence for related myxosporean species were carried out, and these organisms include 6 populations of Myxobolus ampullicapsulatus collected from Chongqing and Jiangxi, and Myxobolus honghuensis isolated from Hubei. Secondly, the molecular phylogeny for Unicauda pelteobagrus, isolated from Pelteobagrus fulvidraco in Chongqing area, was studied based on 18S rDNA sequences. Thirdly, sequence similarity and mutation site, genetic diversity and phylogenic analysis inferred from SSU rDNA sequence, ITS-5.8S rDNA sequences for Henneguya zikawiensis, isolated from Carassius auratus auratus’s gills in Jiangxi area. The analyses were demonstrated:1. There are obvious differences between M. ampullicapsulatus and M. honghuensis in the morphological and molecular data. Research results confirm M. ampullicapsulatus and M. honghuensis were both valid myxosporean species. For those species with close morphological and molecular data and identified difficultly, the host specificity and tissue tropism can be as the important taxonomic basis. Tissue specifity is much more important than the geographic distribution for myxosporeans with close genetic relationship. Analysis on sequence mutation site should be the effective means to distinguish the similar myxosporeans.2. The sequence data of Henneguya sp. WB-LZH from the GenBank database isolated from gills of Carassius auratus auratus is very close to that of Henneguya zikawiensis, and the genetic distance is within the range of intra-species. So Henneguya sp. WB-LZH should be Henneguya zikawiensis.3. The homology between U. caudatus and U. pelteobagrus was far blow the one between U. caudatus and Myxobolus caudatus, which did not support the viewpoint putting U. caudatus and U. pelteobagrus into the same genus --- Unicauda.4. Myxobolus, Henneguya and Unicauda genera could possess a common origin, but also need to be further confirmed. The phenomenon of Myxobolus spores with caudal appendages provides additional evidence that the use of this character to separate Myxobolus and Henneguya into distinct genera is not reflective of an evolution arily accurate classification scheme. The present study also revealed that the validity of genus Unicauda was questionable.