Morphological Taxonomy And Molecular Phylogeny Of Monogenea Parasitizing Fishes From Yunnan Province

Monogeneans are obligate parasites of aquatic and semi-aquatic vertebrate.In view of the host specificity and co-evolution of monogenean-fish associations,parasites of Class Monogenea present strikingly special relationship and idealized experimental paradigm in the research field of origin and development of parasitism.Even the molecular phylogeny of Monogenea leads to new insights on the origins of their early vertebrate hosts while simultaneously phylogenetic relationships of hosts were reconstructed and the historical geographical distribution pattern of host was shaped by the phylogeny of their monogenic flatworms based on genetic molecular data.Monogeneans are significant parasitic disease for fishery industry.It causes gill swelling,pathological changes and necrosis,and even causes death of the fish hosts,which seriously endangers the fishery production of fish fry and species.The biodiversity of class Monogenea are widely diverse with their host fishes of Yunnan Province,where has repeatedly been ranked high in terms of species diversity,such as endemicity and indigene species fishes.Endemically distributed species can better represent the characteristics of fauna and initial radiation and coevolution with monogenean-fish associations.The present reseah focus on the species diversity of monogenic flatworms that parasitizing fishes of Yunnan Province.New taxa and species composition of Monogenea will be described by combination of morphological taxonomy and molecular identification.The validitation of taxa and level of host-parasite specificity will be ascertained.Phylogenetic relationship of host and parasite between genera and cogenerics will be reconstructed based on the sequences information rDNA(ITS 2,and 28 S rDNA).The reseach results provide important scientific data for further revealing difficult problems in classification and inferring the mechanism of monogenean-fish co-evolution events.Of 1262 fishes belong to five orders,11 families,48 species were collected from locality land water or buying from the farmers markets.Totally 425 fishes of 22 species were infected monogeneas naturely,including Cyprinus carpio,C.carpiochilia,C.auratus,Ctenopharyngodon idellus,Hypophthalmichthys molitrix,Aristichthys nobilis,Pseudorasbora parva,Hemiculter leucisculus,Opsariichthys bidens,Anabarilius alburenops,A.macrolepis,Abbottina rivularis,Sikukia gudgeri,S.flavicaudata,Rhodeus ocellatus,R.sinensis,Puntius ticto,Hemibarbus maculatus,Rhinogobius giurinus,Tilapia mossambica,Pelteobagrus fulvidraco and Silurus asotus.Totally 40 species of class Monogenea were collected and described in the present study,which belong to three orders,four families and 11 genera.Taxa are composed of 34 recorded species and six new species,including 29 new Chinese distribution records and 15 new host records.The mean prevalence was 34%(14% to 90%)in this investigation.Genus Dactylogyrus were dominant species for 24 cogeneric species were discovered,of accounting for 60% of the total in this study.The catalogue of taxa with supplementation of recorded species is blew.Dactylogyridae(Polyonchoinea,Dactylogyridae)contains 25 species(24 species in Dactylogyrus and one species in Bivaginogyrus).Ancyrocephallidae contains 11 species(one species separately in Ancyrocephalus,Parancyrocephaloides,Pseudancylodiscoides,and Bychowskyella respectively;two species in Silurodiscoides and four species in Cichlidogyrus).One species in Laminiscus of Gyrodactylidae.Diplozoidae(Oligonchoinea,Discocotylinea)is composed of four species,including one species in Eudiplozoon and three species in Paradiplozoon.Combined morphological and molecular approaches,six new species were identificated,including Dactylogyrus puntius sp.nov.(host P.ticto),D.yunnanensis sp.nov.(host S.flavicaudata),D.rhodeus sp.nov.(host R.ocellatus),C.bannaensis sp.nov.(host T.mossambica),L.leucisculus sp.nov.(host H.eucisculus and H.maculatus)and P.yunnanensis sp.nov.(host S.gudgeri).The type species of genus Bivaginogyrus,Bivaginogyrus obscurus is the first record of geographical distribution from Yunnan province.Laminiscus leucisculus sp.nov.is the second Chinese species of Genus Laminiscus.The results indicated Dactylogyridae presented monophyletic group based on the reconstructed phylogenetic relationship of 28 S rDNA sequence with Thaparocleidus asoti and T.varicus as outgroups.Dactylogyridae(Bychowsky,1933)and Ancyrocephalidae(Bychowsky,1937)were closely related to each other.Dactylogyrus is a stable monophyletic group and this cluster formed a sister group with Cichlidogyrus.The later genus is monophyly comfirmed in the present study.In view of the fact that the species in basic branch of Dactylogyrus cluster infected mostly fishes of subfamily Labeoninae which was suggested as the early invaded host of Dactylogyrus.Based on the ITS 2rDNA sequence with Neoheterobothrium hirame as out group,the genus Paradiplozoon of Diplozoidae is a paraphyletic group.Seven species of Chinese Paradiplozoon were clustered as the most basic branch of the phylogenetic tree,which may suggest that the phylogenetic status of Paradiplozoon in China is primitive.This study supports the existence of intraspecific variations in morphological characteristics of diplozoid monogeneans and agrees that morphological differences and host species are not the most appropriate taxonomic characteristics for identifying taxon.In view of the close relationship between the molecular phylogeny and the geographic distribution of the host,it is considered that further study on the phylogeny of geographic species will provide significance for the classification of Diplozoon.Based on the results of morphological identification and molecular phylogenetic studies,the distribution and population composition of monogeneans from Lancang River,Nanpanjiang River,Yuanjiang River and Irrawaddy River were sorted out.It was concluded that the different faunal characteristics of monogeneans in different land waters were related to the changes of water level during the sampling season,human disturbance and pollution.Monogeneans carried by economic fish species in cage culture could cause the parasite to enter reservoirs and land waters,which will accelerate the evolution of monogenetic fauna to aquaculture type,and bring potential risks of fish diseases.The differences of monogenetic fauna of main river system of Yunnan and relationship between the fauna and epidemiological effection need to be further studied.