| Ariosoma meeki(Anguilliformes,Congridae),also known as a kind of sea eel,anguilla,Conger or Unagi,is an ecologically diverse fish of a large quantity.It inhabits waters of 100 to 400 meters deep,and is mainly distributed in the Indian Ocean and the Northwest Pacific Ocean which covers tropical and subtropical ocean.In China,it mainly appears in the East China Sea and the seas near Taiwan’s southwest and northeast currently.Fishermen catch them mostly by bottom trawling or cages.People make use of Ariosoma meeki by make it into fishmeal.In addition,there is also a small amount of vendors trading it on the street.But due to less research on Ariosoma meeki,its economic value hasn’t been fully realized.The research on the genetic resources of aquatic animals,especially marine fish,is the necessary theoretical basis for the sustainable development of the aquatic industry and ones related to it.What’s more,the classification and identification of marine animals is an important prerequisite for the research of genetic resources of aquatic animal.A certainty of natural or human factors are severely damaging China’s recent aquatic genetic resources.Therefore,the protection and rational use of aquatic genetic resources is the key to maintaining the healthy and sustainable development of China’s aquatic products and other industries.Due to the great controversy about the classification and identification of eels,the genetic resources and exploitation of eels are restricted.The purpose of this article is therefore to improve the utilization and development of eels’ genetic resources by identifying them and providing relevant basic scientific data.So far,about 800 species of Anguidae have been discovered,and they are divided into four suborders according to their morphological characteristics.However,existing classification methods solely based on morphological data are easily questioned,because morphological classification can lead to confusion between different individuals of the same species.Mitochondrial DNA(mt DNA)is an effective molecular marker widely used at this stage,which can distinguish one individual of a certain species.Therefore,the complete mitochondrial genomic DNA can be combined with morphological analysis to verify the identification of Anguidae with higher accuracy.The sample used and identified in this study is an adult Ariosoma meeki collected in the waters near Chongming District,Shanghai,China(N31°37’37.42,E121°21’31.01),and its sample was preserved in the The Marine Animal Herbarium in our laboratory.TIANGEN Marine Animal Genome Extracting Kit(TIANGEN Biotech,Beijing,China)was used to extract genomic DNA from muscle tissue according to the molecular biology instructions provided by the manufacturer.After sequencing it and assembling with mt Maker software,a typical circular mitochondrial DNA with a size of 16,154 bp was obtained(Gen Bank accession number: MN616974).Its overall base composition is:28.42% A,26.54% T,19.65% G and 25.39% C.In addition,the online analysis software DOGMA was used to analyze its sequence(http://dogma.ccbb.utexas.edu/index.html),and a conservative structure was found in its mitochondrial DNA,including 2 r RNA sequences(12S r RNA and 16 S r RNA),13 sequences of genes which code protein(ATPase 6,ATPase 8,COX1,COII,COIII,Cyt B,ND1,ND2,ND3,ND4 L,ND4,ND5,ND6),21 sequences of genes of t RNA(Ala,Arg,Asn,Asp,Cys,Gln,Gly,His,Ile,2 Leus,Lys,Met,Phe,Pro,2 Sers,Thr,Trp,Tyr,Val),and a D-shaped replacement loop of control region(D-loop).All 13 protein coding genes are encoded on the heavy chain.Except for COI(with GTG as the start codon)and ND6(ATC as the start codon),most protein coding genes use ATG as the start codon.Both r RNA genes are encoded on the heavy chain,they have similar characteristics in length(955bp and 1699 bp,respectively),and are similar in sequence characteristics to other eel orders.What is noteworthy is,different from other eel-order mitochondrial DNA,there are two t RNA-Leu and t RNA-Ser on the mitochondrial DNA of A.meeki,but no t RNA-Glu was detected.In this study,a neighbor joining tree was constructed,the purpose of which is to study the phylogenetic location of A.meeki.In the tree,the mt DNA genomic sequences from 36 other species of eel order were used;the mitochondrial DNA sequences of Auxis tazar,Tropheus moorii,and Petrochromis trewavasae were used as the outer group of NJ tree.The result showed that A.meeki is close to Ariosoma shiroanago,and is clearly grouped with other eel species.In summary,the mitochondrial DNA of A.meeki obtained in this study provides important DNA molecular data for related research,which can be used for further analysis of other Anguilla species.In order to further explore the evolutionary relationship of Ariosoma eels and Anguilla eels,a phylogenetic tree was constructed.And it was found that A.meeki has a closer phylogenetic relationship with the A.shiroanago.In addition,in this project,six protein coding genes(ND2,ND4,ND5,COI,COIII,and Cyt B)were selected as potential DNA barcodes for the Ariosoma eels,while interspecies genetic distance and intragenus genetic distance analysis were proceeded respectively.And the result showed that the COI,Cyt B and ND5 genes could be used as more suitable DNA barcodes for the Ariosoma eels.To conclude,this subject demonstrated the genetic relationship of A.meeki with other Anguidae species at the molecular level,and provided valuable evidence and necessary resources for further study of the molecular phylogeny,biogeography and adaptive evolution of this lineage. |
