| Perca fluviatilis belongs to Osteichthyes,Perciformes,Percidae,Perca,and is distributed in the waters of Ergis River and Ulungu Lake in China.In recent years,due to various factors such as human destruction and changes in the ecological environment,the wild population of P.fluviatilis is gradually decreasing,and the P.fluviatilis in Ulungu Lake is almost on the verge of extinction.In this study,species identification,phylogenetic analysis,and infection analysis were carried out on the parasitic Ancyrocephalus on the gills of P.fluviatilis by means of morphology and molecular biology.The mitochondrial genes of P.fluviatilis were sequenced,and a phylogenetic tree was constructed to explore the co-evolutionary relationship between parasites and hosts.The research results provide basic data for species protection and parasitic disease control of wild P.fluviatilis in the Ergis River,and also provide basic data for the study of the co-evolutionary relationship between parasites and hosts.The results are as follows:(1)The morphological observation of the parasitic Ancyrocephalus parasitic on the gills of P.fluviatilis was carried out by morphological methods,and it was found that the morphology was consistent with that of Ancyrocephalus percae.Statistical methods were used to statistic the infection of A.percae parasitic on the gills of P.fluviatilis,and its spatial distribution characteristics were further analyzed.The results showed that their overall infection rate,mean infection abundance and mean infection intensity were18.56% and 0.52 ± 1.7,2.78 ± 3.17,respectively,and 13.40% and 12.37% for the right and left gills,respectively,with no significant difference in their infection abundance(P > 0.05).The mean intensity of infection and mean abundance of infection values in the gill slides did not differ significantly from each other.Significant differences(P < 0.05)in the abundance of infection between all body length groups and all body length groups in the left gill IV for A.percae.A.percae have no preference for parasitism on the left and right gills of the host,and the distribution type in the P.fluviatilis population is mainly aggregation distribution,only the body length group L ≤ 8,the left gill I and gill III and the right gill II are uniform distribution.(2)Amplification of cox1,16 S r RNA,12 S r RNA,18S-ITS1-5.8S r DNA,28 S r DNA and other gene fragments to construct a phylogenetic tree,the results showed that all the Ancyrocephalus in the five evolutionary trees clustered into one branch.The results of the phylogenetic tree constructed based on three mitochondrial genes showed that it was most closely related to the same genus Ancyrocephalus mogurndae,and the genus was most closely related to the Cichlidogyrus;Based on the phylogenetic tree of18S-ITS1-5.8S r DNA and 28 S r DNA genes,it was found that the A.percae amplified in this study was clustered into a branch with A.percae collected in Lake Constance,Germany.and is most closely related to the Ancyrocephalus paradoxus.The Ancyrocephalus is most closely related to the Cleidodiscus,and the clades of Ancyrocephalidae are divided into three branches,namely Ancyrotephalinae,Ancylodiscoidinae,and Pseudomurraytrematinae.(3)The whole mitochondrial genome of the P.fluviatilis collected from the Ergis River was sequenced,and its gene structure was analyzed by comparative genomics,and a multi-gene joint phylogenetic tree was constructed at the same time.The results showed that the full-length mitochondrial genome of P.fluviatilis was 16 537 bp and consisted of 37 genes,including 13 protein-coding genes,22 t RNAs,2 r RNAs and 2non-coding regions,of which 9 genes(nad6,trn E,trn P,trn Q,trn A,trn N,trn C,trn Y and trn S2)are located in the light chain,the rest of the genes are located in the heavy chain,the A + T content in the entire mitochondrial genome is 54.93%,and there are intergenic region and overlapping gene.The typical coding gene has a total of 91 bp Spacer sequence and 28 bp overlapping sequence.Based on the phylogenetic tree constructed from 21 Percoidei species,it was found that P.fluviatilis(MZ461595)and P.fluviatilis(AP005995)were clustered together in this study.P.fluviatilis,Perca flavescens,and Perca schrenkii together form a sister clade located at the base of the evolutionary tree.Genes such as atp8 and nad6 are ideal molecular markers in the study of molecular ecology and population genetics of Percoidei,which can be used to analyze the genetic diversity among different species and populations of Percoidei,and provide a basis for the protection of biological resources and the restoration of biomass basic references.(4)Using the cox1,18S-ITS1-5.8S r DNA,28 S r DNA gene sequences of the species,the phylogenetic trees of the parasite and the host were constructed respectively,and the co-evolutionary characteristics of the two were preliminarily analyzed.In the constructed evolutionary tree,most of the Ancyrocephalidae species are parasitic in perciformes,and each subfamily of Ancyrocephalidae is consistent with the corresponding host fish evolutionary tree,and the evolutionary relationship can be related to the host evolutionary relationship.Correspondingly,there is topological consistency between the parasite and the host,so this study believes that there is a certain degree of co-evolutionary relationship between the Ancyrocephalidae species and their hosts. |
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