A Dissertation Submitted For The Degree Of M.D

Ectoparasitic trichodinids from some economic freshwater fishes,Carassius auratus,Hypophtalmichthys molitrix,Aristichthys nobilis and Ctenopharyngodon idellus in Chongqing,China,were investigated in this work.Six species of two genera submitted to Oligohymenophora Puytorac et al.,1974;Peritrichida Stein,1879; Mobilina Kahl,1933;Trichodinidae Claus,1874;Trichodina Ehrenberg,1838 and Trichodinella(Rabbe,1950) Sramek-Husek,1953:Trichodina reticulata Hirschman & Partsch,1955;Trichodina fahaka Al-Rasheid et al.,2000;Trichodina hyperparasitis Chen & Hsish,1984;Trichodina modesta Lom,1970;Trichodinella nova Tang,2005; Trichodinella epizootica(Rabbe,1950) Sramek-Husek,1953.They were redescribed based on the observation of living body,dry silver impregnation technique and methyl green-pyronin stain.T.fahaka is a new record in China and its new host is the Crucian Carp.Ctenopharyngodon idellus is a new host of T.hyperparasitis.T.modest and T. epizootica now have their new host Ctenopharyngodon idellus.One cause of disease infection forewarns,T.nova can be proliferate fast in the cultivation.18S rDNA sequence segment of which obtain from this work has supplemented the database of trichodinids.T.epizootica and Trichodinella myakkae should be different species base on molecule data.1618bp of T.epizootica are obtained,with the corresponding sequence(1699bp)(T.myakkae,accession number:AY102176.1), homology similarity is 97%.MP and NJ analyses were demonstrated:both trees are consistently in topology,Bootstrap shows almost each clade of the phylogenetic tree has more than 60%similarity of boot-strap value.The sea clade which parasitized in shellfish lies in the root of phylogenetic tree,evolve in the early stage.The distribution of the species parasitized in shellfish and freshwater fishes are in line with the molecular character.The higher similarity of the base sequence,the closer of the relationship.So the phylogenetic tree can reveal the common character and the difference.T.epizootica-T,myakkae and T.nobilis-T,heterodentata are two sister groups in the fresh water clade.The two clades which are remarkably difference in morphology locate in the distal end,while the small difference from 18S rDNA sequence.T.reticulata,T.sinonovaculae and T.ruditapicis which parasitized in shellfish gathered in the same clade shows that they have share the same tropism of the host.35 groups of the data of Trichodinids handled by SPSS,16main morphology classificate indexes refers to the multi-dimensional statistical analysis result which drafts to demonstrate:Each index shows remarkable or the extremely remarkable objective effect.Each index takes higher Communalities,illuminates that when the classifieate indexes transformed,the factor classification still retained quite many information.The first principal component accumulation progress has reached 88.793%, weighted by decreasing order is L1,s,S1,w,L2,dd,1,t,S2,L4,S4,L3,S3.The synthesize estimate of the morphology taxonomy index which lean to denticle size, consistent with classical taxonomy.When the comprehensive information content reaches 95.836%,four principal components are extracted,may sum up as follows:the blade factor,Central part factor,Ray factor,the denticle-link factor.The result of R-cluster analysis consistent with the former,they together promulgate the factors of morphology indexes.The Q-cluster analysis divides the sample into 5 groups,basically according to body size and each similarity of morphology taxonomy index.T.nobilis is remarkable and special in shape character,so separated firstly as groupâ…¤.Cladeâ…¡andâ…¢formed a group which located in the middle of the tree because of it's index perform weakly.The small-sized ones lies in the peak of the tree,mainly displays the blade factor.On this point,molecular phylogenic tree plays equally effect with shape-index method.