Taxonomy And Phylogeny Study Of Lymnaeidae

Lymnaeidae belong to Mollusca,Gastropoda,Pulmonata and Basommatophora.It is one of the four main branches of the superfamily conifera,which is the most abundant and important group of freshwater snails.The species of Lymnaeidae is the important medical shellfish,which can act as the intermediate host for many parasites and harm human health.The morphological and anatomical characteristics of the species from Jiang xi,Hu nan,Yun nan,Guang xi and Gui zhou were described in detail,then we studied its taxonomy and phylogeny combined with the molecular biotechnology.The main results are as follows:1.The collected samples were classified 30 species of 2 genera according to the morphological characteristics of the shells,and the morphological descriptions were given.We measured the shell shape parameters of the30 species and principal coordinata analysis(PCoA)was constructed which revealed the similar variation level of shell shape among the collected species.2.By analyzing the radula characteristics of 19 species in the Lymnaeidae,it was found that the genus could be distinguished according to the size,number and morphological characteristics of central teeth,lateral teeth,inner marginal teeth and outer marginal teeth.In addition,we found that the size and morphological characteristics of the inner and outer marginal teeth could classify most species of Lymnaeidae.Therefore,the radula could be used as an effective basis for species classification in the family Lymnaeidae.3.Morphological characteristics of penial complex of 29 Lymnaeidae species were described in this study.It was found that the anatomical features of penial complex were effective for species classification at genus level,while only a few species could be effectively distinguished within the same genus,for example: Radix plicatula,Radix chefouensis,Radix lagotis costulata,Radix sp.2,Radix sp.4 and Radix sp.8 in the Radix,Galba pervia and Galba palustris in the Galba.For other species,the penial complex was difficult to distinguish effectively.4.Mitochondrial gene COI,16 SrRNA and nuclear gene 28 SrRNA were used to calculate the base composition,intraspecific and interspecific genetic distance of each gene sequence in 170 samples of 30 species based on shell morphology classification,and relevant sequence analysis and phylogenetic analysis were conducted.The results showed the preference of G+C base of nuclear gene 28 SrRNA sequence.Moreover,compared with COI and 16 SrRNA genes,28 SrRNA was relatively conservative,and the phylogenetic tree constructed by it had poor resolution and showed parallel parallel lineage.Mitochondrial COI and 16 SrRNA played an important role in the identification of species,especially in the analysis of multiple genes combined with conformation,which could more accurately reflect the phylogenetic evolution of species.5.The results of morphological,anatomical and molecular phylogenetic studies showed that the collected samples should be integrated into 2 genera and 16 effective species,the following conclusions were drawn: Radix plicatula was closely related to Radix sp.7 and should be combined into one effective species called Radix plicatula.Radix swinhoei was closely related to Radix ovata and should be combined into one effective species called Radix swinhoei.Radix pereger was closely related to Radix sp.1 and and should be combined into one effective species called Radix pereger.Radix rubiginosa was closely related to Radix sp.6 and should be combined into one effective species called Radix rubiginosa.Radix auricularia,Radix larots,Radix acuminata and Radix lagotis costulata although didn't get good support on molecular systematics,but through the comprdix acuminata and ehensive analysis of morphology,anatomy,retain its validity;Although Galba sp.2 and Galba palustris do not form a branch in the phylogenetic tree,their shell morphology and anatomical characteristics were relatively similar to Galba palustris,and their interspecific genetic distance is small,so we temporarily combined them into one effective species called Galba palustris.The 4,7,8,11 and 12 samples in Galba pervia were highly supportive,which was an effective species,and it was called Galba pervia.Radix hookeri,Radix patula,Radix chefouensis,Radix chlamys,Galba truncatula and Galba laticallosiformis were all independent species.The effectiveness of the remaining species will require further study.