Molecular Phylogenetic Study Of Monogenea Of Fish From Partial Basin Of Lancangjiang River And Yuanjiang River Based On Mitochondrial Genome

The fish diversity of Lancangjiang River and Yuanjiang River are remarkably rich among the six major river systems in Yunnan Province,and it is the most abundant in Lancangjiang River.There are a series of achievements and records in the field of Monogenea-fish related systematic research,while the records of Yuanjiang River system are relatively few at this moment.In the present study,a combination research of traditional classification with molecular identification of Monogenea-fish from partial basin of Lancangjiang River and Yuanjiang River was carried out.The main results are as follows:1.A total of 233 fishes belong to 4 orders,10 families,17 genera,18 species were collected from land water or buying from the markets near the Lancangjiang River and Yuanjiang River.Totally 14 species of monogeneans belong to 4 families,6 genera were collected including 13 recorded species,1 unrecorded species and 1new host records.2.The mitochondrial genome of 4 species of Monogeneas,Paradiplozoon yunnanesis,P.hemiculteri,Eudiplozoon nipponicum,and Gyrodactylus sp.were completely sequenced,all 36 standard genes(except atp8 gene)were attained in the present study.The comparative analysis of the mitochondrial genome of 37 species from the database and 4 species in the present study showed that :(1)Among the 41 species studied,the largest mt DNA sequences is Gyrodactylus sp.,about 18165 bp in length;(2)The AT content of Polyonchoinea ranged from 60.0% to 82.6%,reflects the range of AT content change of the group;(4)Relative synonymous codon usage(RSCU)analysis shows that Monogenea preference to AT rich codon.The family Diplozoidae prefers to use GT rich codon;(5)Based on average genetic distance comparisons,Among the coding genes of Monogenea,nad2 and rrn S express faster evolution than cox1 and rrn L genes respectively,nad2 and rrn S are the suitable molecular markers in low-level taxonomic category of phylogenetic reconstruction of Monogenea;(6)The genes are largely rearrangement between the Oligonchoinea and the Polyonchoinea,in the low-level taxonomic category,for instance,rearrangement between the Eudiplozoon spp.and the Paradiplozoon spp.are slightly.However,large-scale rearrangement events occurred between the Gyrodactylus spp.(viviparous)and Aglaiogyrodactylus spp.(oviparous).3.Phylogenetic reconstruction represent of Monogenea based on the mitochondrial genome and ribosomal partial sequences(28 S r DNA、5.8S+ITS2+28 S r DNA and 18 SS r DNA、5.8S+ITS2+ITS1S r DNA、5.8S+ITS2+5.8)showed that :(1)Taxonomic category of Order: Mazocraeidea is located at the base of the phylogram,Dactylogyridea and Capsalidea cluster into one clade,then Clustering with Gyrodactylidea;(2)Taxonomic category of Family: Dactylogyridae are nested in Ancyrocephalidae and cluster into a branch with Ancyrocephalidae.The result supports the systematic view of Boeger and Kritsky,these three families should be identified as Dactylogyridae.In addition,the phylogenetic relationship between the family Capsalidae and the loculidae is closer than that between the family Diplectanidae and the family Capsalidae;(3)Taxonomic category of Genus:Eudiplozoon is a symphytic group,which is the earliest differentiated group in Diplozoidae.In addition,Eudiplozoon and Diplozoon always cluster together,or may belong to the same genus.Aglaiogyrodactylus shows an earlier origin than Gyrodactylus.Due to the lack of data on mitochondrial genome and the significant diversity of Monogenea species,the phylogram based on mitochondrial genome can only reflect the species and taxonomic elements involved in the present study.Therefore,it is necessary to strengthen the research and provide new data,to continue analysis the phylogenetic relationship of each taxon.The related research result may explained the origin of parasitic speciation and early adaptive radiation of the co-evolution of Monogenea-fish association.