Mitochondrial genome structural characteristics and phylogenetic relationships of Dysomma anguillare

【Objective】The mitochondrial genome structural characteristics and phylogenetic relationships of Dy-somma anguillare were investigated so as to provide theoretical basis for species identification and germplasm resource as-sessment of this fish.【Method】The complete mitogenome of D.anguillare was obtained by high-throughput sequencing technology in this study.The gene composition and structure characteristics were analyzed,based on the mitochondrial ge-nome sequence of related fish published by GenBank,the phylogenetic evolutionary tree was constructed using the maxi-mum likelihood method based on the sequence similarity of protein-coding genes (PCGs) to analyze the relationship and evolutionary status of the fish in Anguilliformes.【Result】The total length of mitochondrial genome of D.anguillare was16690 bp,including 13 PCGs,22 tRNA genes,2 rRNA (12S rRNA and 16S rRNA) and 2 non-coding regions (D-loop and O_L).The base composition showed obvious noticeable A/T preference and anti-G-bias.The content of AT in D-loop re-gion was the highest (65.56%).ATG was the most common start codon in PCGs.Six genes used incomplete codons T-and TA-as stop codons.Only tRNA-Ser^(AGN) could not fold into the typical clover shape due to the absence of dihydroura-cil arm among the 22 tRNAs.The motif 5'-TGGCAGAGCCTGG-3'was identified in tRNA-Leu^(UUR),which was highly similar to the binding site of mammalian mitochondrial transcription termination factor (mTERF).The secondary struc-tures of 12S rRNA and 16S rRNA were composed of multiple stem-loops,with the latter more complex than the former.Domain VI of 16S rRNA contained a conserved multibranched loop (CML) homologous to the prokaryotic 23S rRNA peptidyl transferase center (PTC).In D-loop region,extended termination sequence regions (ETAS),central conserved re-gions (CSB-F,CSB-E and CSB-D) and conserved sequence regions (CSB-1,CSB-2 and CSB-3) were identified.The phylogenetic tree constructed based on PCGs sequence similarity demonstrated that the D.anguillare was closely related to Simenchelys parasitica,Ilyophis brunneus and Synaphobranchus kaupii.【Conclusion】The mitogenomic structure of D.anguillare is similar to those of most bony fishes,the total length of the mitochondrial genome is between the range of An-guilliformes fishes,and the phylogenetic relationships supports to place D.anguillare in Synaphobranchidae,Dysomma.