Identification,analysis,prevention And Treament Of A New Leech Species Parasiticing Monopterus Albus

Leeches,belonging to Annelida and Hirudinea,are hermaphroditic and heterozygous,widely distributed in freshwater environments such as oceans,lakes,rivers and wet land.They are an important part of freshwater benthic invertebrates as well as animal parasites.The blood of fish,turtles,soft-shelled turtles,frogs,salamanders,birds and mammals is the main food of leeches,because they have suckers at the front and rear ends of their bodies,and they also serve as temporary external parasites of these animals.Monopterus albus belongs to the order Syngbranchia,Syngbranchaceae,and the eel species.It is one of the important freshwater aquaculture species in my country.Because of its high protein,low fat,and no intermuscular spines,it is deeply loved by consumers.In the process of farming and breeding of Monopterus albus,I found that there are a lot of leech parasites on the surface of the Monopterus albus.In order to effectively solve the leech attack in the process of Monopterus albus farming and increase the production of eel aquaculture,the identification of the leech species,the sequencing of mitochondrial genomes,and the prevention and control of leech disease are specially carried out,aiming to enrich the species of leech in China and promote the healthy,green,and healthy Monopterus albus aquaculture industry efficient development.(1)In this experiment,by making paraffin sections,extracting and amplifying the mitochondrial cytochrome c oxidase subunit 1(COX 1)and 18S ribosomal RNA(18S rRNA)genes of the leech,the external morphological data of the leech were obtained.,internal organ structure and related gene fragments.By analyzing the external morphological data and related molecular biology information of the leech,and combining with the species naming rules,we named the leech Hemiclepsis yangtzenensis(2)In this experiment,the mitochondrial genome of the leech was sequenced,annotated and uploaded to GenBank,combined with the comparison and analysis of the complete mitochondrial genomes of the leech and leech leech that have been completed on NCBI.The results are as follows:The leech mitochondrial genome sequence was annotated and submitted to GenBank(accession number:MN106285).The full-length mitochondrial genome sequence is 14984 bp,encoding a total of 37 genes,namely 22 tRNA genes,2 rRNA genes and 13 protein-coding genes.The percentages of the 4 kinds of bases in the leech are quite different,and the base composition is A(35.12%),G(12.09%),C(15.04%)and T(37.66%),A+T content(72.87%)higher than G+C content(27.13%).There are 12 protein-coding genes(COX 1,COX 2,ATP8,NAD6,CYTB,ATP6,NAD5,NAD4L,NAD4,NAD1,NAD3,NAD2)with ATG as the start codon,and TTG as the start codon of the COX3 gene.There are 7 protein-coding genes(COX 1,COX3,NAD6,CYTB,ATP6,NAD4L,NAD2)with TAA as the stop codon,one protein-coding gene(NAD3)with TAG as the stop codon,and the remaining 5 protein-coding genes(COX 2),ATP8,NAD5,NAD4,NAD1)are incomplete stop codons.A total of 3683 amino acids were translated from 13 protein-coding genes.Compared with the published mitochondrial-encoded protein genes of leech,the COX 1,COX 2,CYTB and NAD1 genes of this leech are relatively conservative,and the ATP8,NAD6 and NAD2 genes have large variation.Among them,the NAD2 gene has the greatest degree of variation.Similar to most leech mitochondria,this leech mitochondrial genomes also contains 22 tRNAs,whose sequence lengths range from 59 bp to 70 bp,and the total length of the tRNA gene sequence reaches 1407 bp.Among the 22 tRNA genes,there are 2 tRNA-Ser(UCN,AGN)and 2 tRNA-Leu(UUR,CUN).Except for the deletion of one ring of Gln,the rest are typical clover-shaped secondary structures.In addition,the leech mitochondrial genome has 6 non-coding regions with a total length of 623 bp,and 13 overlapping regions with a total length of 83 bp.(3)In this experiment,the leech was subjected to a 96-hour acute challenge experiment by using four drugs,such as copper sulfate,potassium permanganate,compound iodine and quicklime,to obtain the safe concentration of the leech and the minimum lethal concentration in 96 hours.And use the 96 h all lethal minimum concentration to carry out the poisoning test to the healthy Monopterus albus,at the same time in conjunction with the toxicity classification standard issued by the State Environmental Protection Administration,the toxicity of these 4 drugs is judged,and the results are as follows:The 24-hour LC50 of copper sulfate,quicklime,potassium permanganate and compound iodine were 1.49,34.67,15.08,13.56 mg/L,respectively,and 48-hour LC50 were 1.16,32.36,14.54,and 11.64 mg/L.The 72 h-hour LC50 were 0.95,29.40,13.50,10.07mg/L,and 96h LC50 were 0.86,27.97,13.09,9.08 mg/L,respectively.Its safe mass concentrations are:0.21,8.46,4.06,2.57 mg/L.In addition,the challenge test was carried out on healthy Monopterus albus with the lowest total lethal concentration of 4 kinds of drugs at 96 h.The results showed that 1.58 mg/L copper sulfate,35.48 mg/L quicklime,15.84 mg/L potassium permanganate and 14.13 mg/L complex iodine had no significant effect on the survival of the Monopterus albus.Combined with the toxicity classification standard issued by the State Environmental Protection Administration(Aquatic Organism Monitoring Manual),copper sulfate is highly toxic,compound iodine is toxic,quicklime and potassium permanganate are weakly toxic.The toxicity of these four drugs to leeches was in the order of copper sulfate>complex iodine>potassium permanganate>quicklime.