The complete mitochondrial genome of the small yellow croaker and partitioned Bayesian analysis of Sciaenidae fish phylogeny

Characterization of Complete Mitochondrial Genome and Phylogeny of Three Echeneidae Species

Species of the family Echeneidae are renowned for their capacity to adhere to various hosts using a sucking disc. This study aimed to examine the mitochondrial genome characteristics of three fish species (Echeneis naucrates, Remora albescens, and Remora remora) within the family Echeneidae and determine their phylogenetic relationships. The findings revealed that the mitochondrial genome lengths of the three species were 16,611 bp, 16,648 bp, and 16,623 bp, respectively, containing 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a D-loop region. Most PCGs utilized ATG as the initiation codon, while only cox I used the GTG as the initiation codon. Additionally, seven genes employed incomplete termination codons (T and TA). The majority of PCGs in the three species displayed negative AT-skew and GC-skew values, with the GC-skew amplitude being greater than the AT-skew. The Ka/Ks ratios of the 13 PCGs did not exceed 1, demonstrating these species had been subjected to purification selection. Furthermore, only tRNA-Ser (GCT) lacked the D arm, while other tRNAs exhibited a typical cloverleaf secondary structure. Bayesian inference (BI) and maximum likelihood (ML) methods were utilized to construct a phylogenetic tree of the three species based on the 13 PCGs. Remora remora was identified as a distinct group, while R. osteochir and R. brachyptera were classified as sister taxa. This study contributes to the mitochondrial genome database of the family Echeneidae and provides a solid foundation for further systematic classification research in this fish group.

The mitochondrial genome and phylogenetic analysis of Rhacophorus rhodopus

Classification of the genus Rhacophorus has been problematic. In particular there has been considerable controversy surrounding the phylogenetic relationships among Rhacophorus rhodopus, R. bipunctatus, and R. reinwardtii. To examine the relationship among these Rhacophorus species, we assembled the complete mitochondrial genome sequence of R. rhodopus. The R. rhodopus genome is 15,789 bp in length with 12 protein-coding genes (PCGs) (losing ND5), two ribosomal genes, 22 transfer RNA genes, and a control region (D-loop). Base composition of the overall sequence was 60.86% for A + T content and 39.14% for C + G content. Most of the PCGs used ATG as a start codon, except for the COX I gene, which used the ATA start codon. COX I and ND6 used AGG and ATP8 stop codons respectively, while ND3 and ND4L used the TAA stop codon. For the remaining seven genes, the stop codons was incomplete. In addition, both 5' and 3' of the control areas had distinct repeating regions. Based on three datasets and two methods (Bayesian inference (BI) and maximum likelihood (ML)), we reconstructed three phylogenetic trees to explore the taxonomic status of the species and the phylogenetic relationship among R. rhodopus, R. bipunctatus and R. reinwardtii. Our results indicated that these three species are non-monophyletic; thus, the phylogenetic relationship among them is complex and difficult to determine. Further, R. rhodopus is divided into three lineages from different parts of China. The two Rhacophorus samples showed very close phylogenetic relationship with R. rhodopus. Our results add to the mitochondrial genome database of amphibians and will help to disentangle the phylogenetic relationships within the Rhacophoridae.

Sequencing and Characterization of Mitochondrial Protein-Coding Genes for Schizothorax niger (Cypriniformes: Cyprinidae) with Phylogenetic Consideration

The present study was conducted to get more information about the genome and locate the taxonomic position of Schizothorax niger in Schizothoracinae through mitochondrial 13 protein-coding genes (PCGs). These PCGs for S. niger were found to be 11409 bps in length ranging from 165 (ATPase 8) to 1824 bps (NADH dehydrogenase subunit 5) and encode 3801 amino acids. In these PCGs, 4 genes overlap on the similar strands, while one shown on the opposite one: ATPase 6+8 and NADH dehydrogenase subunit 4+4L overlap by 7 nucleotides. Similarly, ND5-ND6 overlap by 4 nucleotides, while ATP6 and COIII overlap by 1 nucleotide. Similarly, four commonly used amino acids in S. niger were Leu (15.6 %), Ile (10.12 %), Thr (8.12 %), and Ala (8.7 %). The results presented that COII, COIII, NDI, ND4L, and Cytb had substantial amino acid conservation as compared to the COI gene. Through phylogenetic analysis, it was observed that S. niger is closely linked with S. progastus, S. labiatus, S. plagiostomus, and S. nepalensis with high bootstrap values. The present study provided more genomic data to know the diversity of the mitochondrial genome and its molecular evolution in Schizothoracinae.

The complete mitochondrial genome of Acanthogobius stigmothonus (Perciformes, Gobiidae)

The complete mitochondrial genome of Acanthogobius stigmothonus is first sequenced in this study. This genome was 16,666 bp in size and contained 37 classic genes, including 13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes. The gene organization and nucleotide composition were the same with those found in most other Gobiidae fishes. Among 37 genes, 28 were encoded by the heavy strand, while nine were encoded by the light strand. The total nucleotide composition of this genome was 27.4% for adenine (A), 17.6% for guanine (G), 28.2% for cytosine (C), and 26.8% for thymine (T), with a high A + T content of 54.2%. This study will provide a better understanding of population genetic diversity of A. stigmothonus and offer useful information for future studies concerning Gobiidae mitogenome evolution.

A first genetic linage map construction and QTL mapping for growth traits in Larimichthys polyactis

Larimichthys polyactis is a commercially important marine fish species in Eastern Asia, yet very few genetic resources exist. In particular, genetic linkage maps are critical tools for genetic breeding. In this study, we generated a high resolution linkage map from a family of 110 individuals and their parents by resequencing the individuals. 3,802 effective SNPs were mapped to 24 linkage groups (LGs). The map spanned 2,567.39 cm, with an average marker interval of 0.66 cm. We used the map to conduct QTL analysis for growth traits, and found 31 markers were significantly associated with growth-related traits. Specifically, three SNPs were identified for total length, nineteen SNPs for body length, and nine SNPs for body weight. The identified SNPs could explain 15.2-22.6% of the phenotypic variation. SNPs associated with growth traits were distributed on LG6 and LG11, and candidate genes included, kif26b, bat1, gna1, gbgt1, and amfr, which may regulate growth. The linkage map and mapped QTLs would be useful for improving the quality of L. polyactis via marker-assisted selection.

Two complete mitochondrial genomes of Myloplus rubripinnis and Metynnis hypsauchen (Characiforme: Serrasalmidae)

Myloplus rubripinnis and Metynnis hypsauchen are two compressed-bodied ornamental fishes of Serrasalmidae family. In this study, complete mitochondrial genome sequences of the two species were determined. The mitogenomes were 16662 bp and 16737 bp nucleotides in length, and both contained 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNA), 2 ribosomal RNAs (rRNA) and a control region. The phylogenetic tree revealed that Myloplus rubripinnis was closely related to Myleus sp. and Myleus cf. schomburgkii, while Metynnis hypsauchen was related to Pygocentrus nattereri, and then the two clades clustered into one group. Present mitogenome sequences of M. rubripinnis and M. hypsauchen will provide molecular information to the evolution and ecology studies of the two species.

Particular gene order and complete mitochondrial genome of Ariosoma meeki (Congridae, Ariosoma)

Ariosoma meeki (A. meeki) is a demersal and carnivorous fish species belongs to the family Congridae. Some wild populations of A. meeki are in danger because of the overfishing and environmental pollution. In order to better understand the germplasm resources, the complete mitochondrial genome of A. meeki was firstly determined in this study. The complete mitochondrial genome is 16,404 nucleotides, comprising 12 protein-coding genes, 2 ribosomal RNA genes, 20 tRNA genes, and 2 main non-coding regions, but ND6 and two tRNA genes were not found in the A. meeki mitogenome. The A. meeki mitogenome was currently the first member of Ariosoma genus with gene and tRNA deletion. In addition, phylogenetic analysis result demonstrated that A. meeki and A. shiroanago were clustered in a clade and formed a sister relationship.

Complete mitochondrial genome of Caranx equula (Perciformes, Carangidae): genome characterization and phylogenetic analysis

Caranx equula is an important marine fish which due to its commercial values. However, some wild populations of C. equula are in danger because of the overfishing and environmental pollution. In this study, the complete mitochondrial genome of C. equula was firstly determined. The complete mitochondrial genome is 16,607 base pairs in length, and contained 13 protein-coding genes and 2 ribosomal RNA genes, 22 tRNA genes and 2 main non-coding regions. Overall A + T content was 52.9%. In addition, a phylogenetic tree was constructed using the complete mitochondrial genome and showed that C. equula clustered in a clade and formed a sister relationship with Caranx ignobilis belonged to the family of Carangidae.

Complete mitochondrial genome of Red bigeye (Priacanthus macracanthus): genome characterization and phylogenetic analysis

Red bigeye, Priacanthus macracanthus, a species in the family Priacanthidae was added to the seafood red list by Greenpeace International due to the decline in its abundance and overfishing. To understand the phylogenetic relationship of Red bigeye in teleost, we determined the complete mitochondrial genome of Red bigeye. The complete mitochondrial genome is 17,003bp in length, including 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and 2 main non-coding regions. Phylogenetic tree shows that Red bigeye is clustered with the fishes of the order Perciformes.

Characterization of the Complete Mitochondrial Genome Sequences of Three Croakers (Perciformes, Sciaenidae) and Novel Insights into the Phylogenetics

The three croakers (Nibea coibor, Protonibea diacanthus and Argyrosomus amoyensis, Perciformes, Sciaenidae) are important commercial species inhabiting the Eastern Indian Ocean and Western Pacific. Molecular data employed in previous research on phylogenetic reconstruction have not been adequate and complete, and systematic and comprehensive phylogenetic relationships for these fish are unresolved. We sequenced the complete mitochondrial genomes of the three croakers using next-generation sequencing for the first time. We analyzed the composition and phylogenies between 19 species in the family Sciaenidae using the mitochondrial protein coding sequences of 204 species in the Series Eupercaria. We present the characterization of the complete mitochondrial genome sequences of the three croakers. Gene arrangement and distribution of the three croakers are canonically identical and consistent with other vertebrates. We found that the family Sciaenidae is an independent branch that is isolated from the order Perciformes and does not belong to any extant classification. Therefore, this family is expected to belong to a new classification at the order level and needs further analysis. The evolution of Sciaenidae has lagged far behind the Perciformes differentiation. This study presents a novel insight into the phylogenetics of the family Sciaenidae from the order Perciformes and facilitates additional studies on the evolution and phylogeny of Series Eupercaria.

Comparative analysis of the complete mitochondrial genomes of three geographical topmouth culter (Culter alburnus) groups and implications for their phylogenetics

Topmouth culter (C. alburnus) is an important commercial fish in China. We compared the nucleotide variations in the mtDNA genomes among three geographical groups of Culter alburnus: Liangzi Lake, Hubei Province (referred to as LZH); Taihu Lake, Jiangsu Province (TH); and Poyang Lake, Jiangxi Province (PYH). The similarity of whole mtDNA genomes ranged from 0.992 to 0.999. The similarity among 13 protein-coding genes, 2 rRNA genes, and the D-loop sequences was found to range from 0.982 to 0.996. This is useful data for future designing work for making specific molecular marker for distinguishing individuals of C. alburnus from the three geographical groups. An extended termination-associated sequence (ETAS) and several conserved blocks (CSB-F, CSB-E, CSB-D, CSB1, CSB2, and CSB3) were identified in the mtDNA control regions. A phylogenetic analysis shows a monophyletic relationship of the LZF-female and the LZF-male. However, the analysis also showed paraphyletic relationships for the other two geological groups. This result will be useful for the future breeding work of C. alburnus.

Complete mitochondrial genome of Japanese bigeye (Pristigenys niphonia): genome characterization and phylogenetic analysis

The Japanese bigeye (Pristigenys niphonia) is a species in the genus Pristigenys and in the family Priacanthidae. To understand the phylogenetic relationship of Japanese bigeye in teleost, we firstly determined the complete mitochondrial genome of Japanese bigeye. The entire mitochondrial genome of Japanese bigeye is 16,519bp in length, including 13 protein-coding genes and 2 ribosomal RNA genes (rRNA), 22 transfer RNA genes (tRNAs), and 2 main non-coding regions. The overall base composition is 24.9% of T, 30.6% of C, 27.7% of A, and 16.8% of G. The gene arrangement, base composition, and tRNA structures of the complete mitochondrial genome of Japanese bigeye is consistent with those of other teleost. The complete mitochondrial genome of Japanese bigeye was used to construct phylogenetic tree, which shows that Japanese bigeye is clustered with the fishes of the order Perciformes. We expect that the availability of mitochondrial genome of Japanese bigeye will facilitate the further investigations of the taxonomic resolution, biogeography, and molecular systematic.

Particular gene order and complete mitochondrial genome of Beach conger (Conger japonicus)

Beach conger (Conger japonicus) is a demersal and carnivorous species belonging to the family Congridae. In the present study, the complete mitochondrial genome of the C. japonicus was first determined. The mitochondrial genome of C. japonicus is 17,778 nucleotides, comprising 13 protein-coding genes, 2 ribosomal RNA genes, 22 tRNA genes, and 2 main non-coding regions (the control region and the origin of the light strand replication), which is consistent with other vertebrates. However, its gene order is different from other vertebrates (except for C. myriaster). The Cytb gene, tRNA^Thr and the control region are located between the ND5 gene and the ND6 gene in C. japonicus while they are between the ND6 gene and the tRNA^Phe gene in other vertebrates. The same gene order also appeared in C. myriaster. The mitochondrial genome of C. japonicus and C. myriaster, which are currently the only two members of Conger genus with complete mitochondrial genome, appeared in the gene rearrangement, so we speculated that the mitochondrial genome of all species from Conger genus may appear in the gene rearrangement. However, to clarify the speculation, more mitochondrial genomes of Conger genus will be needed in the future. In addition, phylogenetic analysis result demonstrated that C. japonicus and C. myriaster clustered in a clade and formed a sister relationship.

Complete mitochondrial genome of black-banded trevally (Seriolina nigrofasciata): Genome characterization and phylogenetic considerations

The black-banded trevally (Seriolina nigrofasciata) is a species of the family Carangidae and the only known member of genus Seriolina. To understand the phylogenetic relationship of black-banded trevally in teleost, we first determined the complete mitochondrial genome of black-banded trevally. The entire mitochondrial genome of black-banded trevally is 16 531 bp in length, containing 13 protein-coding genes and 2 ribosomal RNA genes (rRNA), 22 transfer RNA genes (tRNAs), and 2 main non-coding regions. The overall base composition is T 25.8%, C 30.0%, A 26.7%, and G 17.5%. The gene arrangement, base composition, and tRNA structures of black-banded trevally are consistent with those of other teleost. Two of the central conserved sequence blocks (CSB-2 and CSB-3) were identified and the core sequence (TACATGTATGTA) of terminal-associated sequences was recognized in the control region. Meanwhile, the conserved motif 5'-GCCGG-3' was identified in the origin of light-strand replication of black-banded trevally. The complete mitochondrial genome of black-banded trevally was used to construct phylogenetic tree, which shows that black-banded trevally is clustered with the fishes of the genus Seriola. We expect that the availability of the mitochondrial genome of black-banded trevally will facilitate the further investigations of molecular systematic and phylogenetic analysis of the Carangidae.

Complete mitochondrial DNA sequence of the endangered fish (Bahaba taipingensis): Mitogenome characterization and phylogenetic implications

To understand the systematic status of Bahabataipingensis within Sciaenidae, the complete mitochondrial genome (mitogenome) sequence of Chinese bahaba has recently been determined by long PCR and primer walking methods. The complete mitochondrial genome is 16500 bp in length and contains 37 mitochondrial genes (13 protein-coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes) as well as a control region (CR) as other bony fishes. Within the control region, we identified the

extended termination associated sequence domain

(ETAS), the central conserved sequence block domain (CSB-D, SCB-E and CSB-F) and the conserved sequence block domain (CSB-1, CSB-2 and CSB-3). Phylogenetic analyses revealed that Bahabataipingensis is more closely related to Pseudosciaeniae than Argyrosominae and Sciaeninae. Additionally, Bahabataipingensis is the sister taxon of Miichthysmiiuy, and those two are sister to Collichthys plus Larimichthys.

Development and preliminary evaluation of a genomewide single nucleotide polymorphisms resource generated by RAD-seq for the small yellow croaker (Larimichthys polyactis)

Recent advances in high-throughput sequencing technologies have offered the possibility to generate genomewide sequence data to delineate previously unidentified genetic structure, obtain more accurate estimates of demographic parameters and to evaluate potential adaptive divergence. Here, we identified 27 556 single nucleotide polymorphisms for the small yellow croaker (Larimichthys polyactis) using restriction-site-associated DNA (RAD) sequencing of 24 individuals from two populations. Significant sources of genetic variation were identified, with an average nucleotide diversity (π) of 0.00105 ± 0.000425 across individuals, and long-term effective population size was thus estimated to range between 26 172 and 261 716. According to the results, no differentiation between the two populations was detected based on the SNP data set of top quality score per contig or neutral loci. However, the two analysed populations were highly differentiated based on SNP data set of both top FST value per contig and the outlier SNPs. Moreover, local adaptation was highlighted by an FST -based outlier tests implemented in LOSITAN and a total of 538 potentially locally selected SNPs were identified. blast2go annotation of contigs containing the outlier SNPs yielded hits for 37 (66%) of 56 significant blastx matches. Candidate genes for local adaptation constituted a wide array of biological functions, including cellular response to oxidative stress, actin filament binding, ion transmembrane transport and synapse assembly. The generated SNP resources in this study provided a valuable tool for future population genetics and genomics studies of L. polyactis.

Complete mitochondrial genome of banjofish (Banjos banjos): genome characterization and phylogenetic analysis

The banjofish (Banjos banjos) is the only species in the monotypic genus Banjos and in the family Banjosidae. To understand the phylogenetic relationship of banjofish in teleost, we firstly determined the complete mitochondrial genome of banjofish. The entire mitochondrial genome of banjofish is 16 485 bp in length, including 13 protein-coding genes and 2 ribosomal RNA genes (rRNA), 22 transfer RNA genes (tRNA) and a control region (CR). The overall base composition is T, 26.2%; C, 29.2%; A, 28.6% and G, 16.0%. The central conserved sequence blocks (CSB) were identified and the core sequence (ACATATATGT) of terminal-associated sequences was recognized in the control region. The gene arrangement, base composition, and tRNA structures of the complete mitochondrial genome of banjofish is consistent with those of other teleost. The complete mitochondrial genome of banjofish was used to construct phylogenetic tree, which shows that banjofish is clustered with the fishes of the family Histiopteridae. We expect that the availability of mitochondrial genome of banjofish will facilitate the further investigations of the taxonomic resolution, biogeography and molecular systematic.

Characteristics and phylogenetic analysis of the complete mitochondrial genome of Cheilodactylus quadricornis (Perciformes, Cheilodactylidae)

The complete mitochondrial genome of the Cheilodactylus quadricornis was firstly determined in the present study. The mitochondrial genome of C. quadricornis is 16 521 nucleotides, comprising 13 protein-coding genes and 2 ribosomal RNA genes, 22 tRNA genes and 2 main non-coding regions (the control region and the origin of the light-strand replication). The overall base composition was T, 26.3%; C, 29.6%; A, 27.8% and G, 16.3%. The gene arrangement, base composition, and tRNA structures of the complete mitochondrial genome of C. quadricornis is similar to other teleosts. Only two central conserved sequence blocks (CSB-2 and CSB-3) were identified in the control region. In addition, the conserved motif 5'-GCCGG-3' was identified in the origin of light-strand replication of C. quadricornis. The complete mitochondrial genome of C. quadricornis was used to construct phylogenetic tree, which shows that C. quadricornis and C. variegatus clustered in a clade and formed a sister relationship. This mitogenome sequence data would play an important role in population genetics and phylogenetic analysis of the Cheilodactylidae.

Complete mitochondrial genome of the natural triploid loach, Misgurnus anguillicaudatus (Teleostei: Cypriniformes: Cobitididae)

Abstract The complete mitochondrial genome of the natural triploid loach Misgurnus anguillicaudatus is a circular molecule of 16,646 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes and 2 main noncoding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and 8 tRNAs. The control region is 918 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the triploid M. anguillicaudatus.

Complete mitochondrial genome of the natural pentaploid loach, Misgurnus anguillicaudatus (Teleostei: Cypriniformes: Cobitididae)

The complete mitochondrial genome of the natural pentaploid loach Misgurnus anguillicaudatus is a circular molecule of 16,643 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and two main noncoding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 918 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the pentaploid M. anguillicaudatus.

Complete mitochondrial genome of Schizopygopsis malacanthus (Teleostei: Cypriniformes: Cyprinidae)

The complete mitochondrial genome of Schizopygopsis malacanthus is a circular molecule of 16,677 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 main non-coding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 938 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the S. malacanthus.

Comparative analysis of mitochondrial genomes in distinct nuclear ploidy loach Misgurnus anguillicaudatus and its implications for polyploidy evolution

Misgurnus anguillicaudatus has several natural ploidy types. To investigate whether nuclear polyploidy have an impact on mitochondrial DNA (mtDNA), the complete mitochondrial genomes (mitogenomes) of five distinct ploidy M. anguillicaudatus (natural diploid, triploid, tetraploid, pentaploid and hexaploid), which were collected in central China, were sequenced and analyzed. The five mitogenomes share the same gene arrangement and have similar gene size, base composition and codon usage pattern. The most variable regions of the mitogenome were the protein-coding genes, especially the ND4L (5.39% mutation rate). Most variations occurred in tetraploids. The phylogenetic tree showed that the tetraploid M. anguillicaudatus separated early from other ploidy loaches. Meanwhile, the mitogenomes from pentaploids, and hexaploids have the closest phylogenetic relations, but far from that of tetraploids, implying that pentaploids and hexaploids could not be formed from tetraploids, possibly from the diploids and triploids. The genus Misgurnus species were divided into two divergent inter-genus clades, and the five ploidy M. anguillicaudatus were monophyletic, which support the hypotheses about the mitochondrial introgression in loach species.

Complete mitochondrial genome of the Amur weatherfish, Misgurnus mohoity (Teleostei: Cypriniformes: Cobitididae)

The complete mitochondrial genome of the Amur weatherfish, Misgurnus mohoity is a circular molecule of 16,566 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 main non-coding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 915 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the M. mohoity.

Mitochondrial genome of the natural tetraploid loach Misgurnus anguillicaudatus

The mitochondrial genome of the natural tetraploid loach Misgurnus anguillicaudatus is a circular molecule of 16,645 bp in length, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and two main noncoding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. All the protein-coding genes are initiated with ATG except for COX1, which began with GTG instead. However, the termination codons of 13 protein-coding genes are varied with TAA, TA-, T-- or TAG. The control region is 917 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the tetraploid M. anguillicaudatus.

Complete mitochondrial genome of the natural hexaploid loach, Misgurnus anguillicaudatus (Teleostei: Cypriniformes: Cobitididae)

The complete mitochondrial genome of the natural hexaploid loach Misgurnus anguillicaudatus is a circular molecule of 16,643 bp in size, containing 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes and 2 main noncoding regions (the control region and the origin of the light strand replication). Most of the genes are encoded on the heavy strand, except for ND6 and eight tRNAs. The control region is 918 bp in length and located between the tRNA(Pro) and tRNA(Phe) genes, some typical conserved elements (TAS, CSB1-3 and CSB D-F) were found in this region. All these features reflect a typical vertebrate mitochondrial gene arrangement of the hexaploid M. anguillicaudatus.