Systematics Research On Five Species Of Plagiorchioidea And Paramphistomoidea Of Yunnan Province Based On Mitogenome

As one of the dominant species parasitizing vertebrate hosts,Digenea present remarkable species biodiversity,which recorded more than 18,000 species of 25 superfamilies,148 families,and over 2,700 genera worldwide.However,the taxonomic status,phylogenetic relationship or status of some families and genera in the subclass of Digonimiasis,which have not been agreed.Among them,the common and worldwide distribution of the Plagiorchioidea and Paramphistomoidea are quite divergent in their classification.In this study,the methods of morphological identification,molecular phylogeny and comparative genomics were combined,based on the partial sequence of cox1,18 S r DNA and the structural characteristics of the mitogenome to study the morphological identification and phylogenetic relationships of Plagiorchioidea and Paramphistomoidea of Digenea parasitizing fish and amphibian.The research results provided new molecular identification features of Digenea,analyzed the mitogenome characteristics of some them,and reconstructed the phylogenetic relationship of some species of Plagiorchioidea and Paramphistomoidea at higher order from the level of mitogenome.The main results are as follows:1.62 specimens of 3 species of frog belong to 1 family,2 genera from Qujing city and 2 specimens of 1 species of fish from Erhai Lake were collected respectively.Of 5species of 4 families of 4 genera digeneans were classified,which are parasitic in different fishes and frogs,these species are as follows: Glypthelmins quieta parasitize Rana grahami,Glypthelmins sp.parasitize R.chaochiaoensis,Haematoloechus claudecombesi parasitize R.grahami and Nidirana pleuraden,and Diplodiscus nigromaculati parasitize R.grahami and N.pleuraden and Orientocreadium indicum parasitize Pseudobagrus fulvidraco.2.The annotation of mitogenome of 5 species of Digenea in the present study showed that:(1)Among them,4 species of Digenea has 36 genes,including 12 proteincoding genes,22 t RNA genes and 2 r RNA genes,but trn E gene deletion in the remaining trematode O.indicum;(2)The dihydrouridine(DHU)arm of trn S1 gene and thymidine-pseudouridine-cytidine(T?C)arm of trn T gene are missing in Glypthelmins sp.,H.claudecombesi and D.nigromaculati.However,the DHU arm of trn S2 gene and T?C arm of trn T gene are missing in O.indicum;(3)Only the DHU arm of trn S1 gene is missing in G.quieta;(4)Microsatellite-like DNA sequences were detected in the non-coding regions of H.claudecombesi and D.nigromaculati.The results of comparative genomics showed that:(1)The high AT bias in both Plagiorchioidea and Paramphistomoidea;(2)The AT skew of mitogenome of Plagiorchioidea and Paramphistomoidea is positive,and the GC skew is negative,which is opposite to that of vertebrates;(3)cox1 gene is conserved in both Plagiorchioidea and Paramphistomoidea;(4)The exchange of trn E and trn G genes in all reported species of Paramphistomoidea.3.Phylogenetic reconstruction of Digenea in this study based on the partial sequences of cox1,18 S r DNA and mitochondrial genome showed that:(1)This study do not support the inclusion of Glypthelmins into the Haematoloechidae based on the phylogenetic relationship of 18 S r DNA of 11 species of Digenea;(2)Taking Plagiorchis maculosus of the Plagiorchiidae and G.hyloreus of the Glypthelminthidae as outgroups,7 species of the Haematoloechus in Americas gathered separately as the basic branch of the phylogenetic tree based on the partial sequence of cox1,then converged with Asian Haematoloechus,and then converged with African Haematoloechus,which is consistent with the origin and spread of Ranoidae from Africa in the early stage.We speculate that Haematoloechus,a parasite of African frogs,may have entered the Asian continent and evolved into the Asian Haematoloechus in the early Tertiary;(3)The species of Orientocreadiidae are a separate branch,which supports the independence of Orientocreadiidae by phylogenetic tree of taking Echinostoma chankensis as the outgroup and based on the cox1 partial sequence;(4)The phylogenetic tree of 18 S r DNA showed that Diplodiscus species have larger genetic distance in different geographical regions and smaller genetic distance in the same region.It is considered that this group has strong geographical affinity.The phylogeny analysis using mitogenome shows that species of Diplodiscus is not clustered with species of Paramphistomoidea,so it is considered that Diplodiscus should attach to Diplodiscidae.