Morphological And Molecular Identification Of The Invasive Snail Biomphalaria Straminea And Four Species Of Planorbidae In China

The Planorbidae species are widely distributed in freshwater waters around the world.Because of most species of Planorbidae are intermediate hosts for a variety of parasites,which can transmit parasitic diseases and do serious damage to the health of people.They have attracted extensive attention from the epidemic prevention department.The Planorbidae were identified and classified based on traditional taxonomic characteristics,including the shape of shell,radula and anatomical features.However,due to the variability of phenotypic characteristics and the lack of many morphology and anatomy materials of the Planorbidae species,it is difficult to identify the species.In this paper,we collected five Planorbidae species specimens in the surrounding waters of Jiangxi Province and Shenzhena,and studied the characteristics of the shells,radula and the anatomical characteristics of the reproductive system.At the same time,based on mitochondrial COI gene sequences and 16 S gene sequence as DNA barcoding,in order to identify five species of Planorbidae.The main conclusions are as follows:(1)In this study,the morphological characteristics of the five species of Planorbidae were described.The average value of shell height and shell diameter between the population was analyzed by one-way ANOVA,the results showed that there were significant differences in the ratio between the shell height and shell diameter of the five groups of Planorbidae(F = 49.729,P <0.01).The characteristics of the radula,including the number of radula,the shape of the central tooth;lateral tooth and marginal toot,and the number of teeth in each longitudinal column were described.For example,the number of radula columns in Biomphalaria straminea is the highest,totaling 67 columns.The number of radula columns in Gyraulus parvus is the lowest,totaling 29 columns.The central tooth of Biomphalaria straminea is wide-tapered;the central tooth of Hippeutis umbilicalis is pointed cone;the central tooth of Hippeutis cantori is pointed cone;the central tooth of Gyraulus parvus is looking like fingers,and the central tooth of Gyraulus convexiusculus is tapered.The reproductive system of five species of Planorbidae was dissected.The obivious difference is the penis complex.The prepuce of the Biomphalaria straminea is cylindrical,with a retractor muscle of preputium on the left and right sides.The prepuce of the Hippeutis umbilicalis has a retractor muscle of preputium and a set of accessory duct,and the end of the penial sheath with a pair of long flagellum.The prepuce of Hippeutis cantori has a retractor muscle of preputium and a long accessory duct and with a pair of long flagellum in end of the penial sheath.The penis complex of species of Gyraulus genus with a narrow middle and thick head and tail,the back of the prepuce has a retractor muscle of preputium,and the penial sheath contains a stylet.And the parameters of the penial complex are measured and the morphology of the penis complex and the variance analysis results were significantly different.(2)The full length of the mitochondrial genome of Biomphalaria straminea was 13,650 bp.It consists of 37 typical animal mitochondrial genes,comprising 13 protein-coding genes,22 transfer RNA genes and 2 ribosomal RNA genes.The base composition of the mitochondrial genome was AT-biased.The H-strand contained most of the genes: 9 protein-coding genes,rrnL gene,and 14 tRNA genes.Four protein-coding genes,rrnS gene,and 8 tRNA genes were located on the L-strand The PCGs of the mitochondrial genome use ATT,ATA,and TTG as the initiation codon,and use TAA or TAG as stop codons.The phylogenetic tree was constructed by the complete genomic sequence of Biomphalaria straminea and the mitochondrial genome sequences of other snails in GenBank database.Phylogenetic analysis showed that the relationship of Biomphalaria straminea and Biomphalaria glabrata was more closed.(3)From the molecular perspective to investigate the applicability of the mitochondrial COI gene sequence and the 16 S gene sequence for species identification and classification of the five species of Planorbidae.The intraspecific genetic distance and interspecific genetic distance of each gene of five species of Planorbidae were calculated.The results showed that the intraspecific genetic distance of COI gene was between 0.000-0.008;the interspecific genetic distance was 0.131-0.165.The intraspecific genetic distance of 16 S rRNA gene was 0.000-0.096;the interspecific genetic distance was 0.134-0.34.The phylogenetic results showed that,the identification results of COI gene in species level and genus level are consistent with the results of traditional taxonomic identification.The identification results of 16 S gene in the genus level are consistent with the traditional taxonomic identification results,while there are some differences in the species level.In this study,the mitochondrial COI gene sequence is more suitable as the DNA barcoding for the identification of the five species of Planorbidae.