Study On Classification, Population Ecology And Molecular Systematics Of Diplozoid In Ergis River

Diplozoid is a parasite of fish, widely distributed throughout the world. Diplozoid belongs to Platyhelminthes, Monogenea, Mazocraeidea, Diplozoinae. In this article, with the traditional method of parasite identification, conventional fish parasitology survey methods, biometrical method and modern molecular biology techniques, we studied the classification, population dynamics and phylogeny of Diplozoid in Ergis fish. The main results are as follows:(1) Through field surveys, five Diplozoid species were collected and identified. Respectively, Diplozoon paradoxum Nordmann, 1832, Paradiplozoon homoion Bychowsky et Nagibina,1959, Paradiplozoon gracile Reichenbach Klinke,1961, Paradiplozoon skrjabini(Achmerov,1974) Khotenovsky,1985, Eudiplozoon nipponicum(Goto, 1891) Khotenovsky, 1985). Of them, Diplozoon paradoxum, Diplozoon, Paradiplozoon homoion, and Paradiplozoon gracile were new records in China. We drew their characteristic figures and described the morphological features.(2) The experiments were examined 373 Abramis brama orientalis Berg, 1949, 173 Cyprinus carpio Linnaeus,1758, 209 Leuciscus leuciscus baicalensis Dybowski,1874, 234 Rutilus rutilus lacustris Pallas, 1811, 140 Gobio gobio acutipinnatus Men’schikov, 1939. Statistical results show that the mean prevalence and the mean infection intensity of five parasites collect from five fishes were: Diplozoon paradoxum 28.69% 5.46, Eudiplozoon nipponicum 1.73% 2.33, Paradiplozoon skrjabini 4.78% 1.6, Paradiplozoon homoion 3.42% 1.75, Paradiplozoon gracile 27.14% 4.21. The cases of Abramis brama orientalis infected Diplozoon paradoxum is the most serious and Gobio gobio acutipinnatus infection Paradiplozoon gracile is followed. Similar infection remaining three kinds of fish, a lesser degree of infection. The five kinds of host fish were segmented according to body length to study the relationship between body length of fish and Diplozoid infections. The fish of larger body length have more Diplozoid to parasite in general.(3) This paper has revealed the feature of population dynamics of Diplozoon paradoxum by means of field sampling investigation Diplozoon paradoxum Nordmann was found in gills of Abramis brama orientalis Berg.The results showed the infection rate of Diplozoon paradoxum was 24.16% and its mean infection intensity was 4.19, the infection rates increase along with the body length, has a tendency to rise in L≤30cm. The infection rate of Diplozoon paradoxum was the highest is in 25cm<L≤30cm with 42.11%,but no Diplozoon paradoxum infection is among more than 30 cm. The Diplozoon paradoxum take the aggregation distribution in different host body length group.(4) We determined the ITS-2 rDNA sequences of five Diplozoid species by conventional molecular biology techniques and obtained their NCBI accession numbers(KP326299,KP340972~KP340975). Using ITS-2rDNA gene sequences to build Diplozoid evolutionary tree. Diplozoon paradoxum and Diplozoon nipponicum respectively clustered in one clade with the insect species found in other parts. Through the ITS-2 sequence alignment of Paradiplozoon gracile, Paradiplozoon homoion and Paradiplozoon skrjabini found that three genetic homology is extremely high,but in the morphology have different characteristics.