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AbstractThe mitogenome of Euphausia crystallorophias collected from the Ross Sea Region Marine Protected Area (RSR MPA) is described for the first time. The assembled mitogenome was 17,291 bp in length and consisted of two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), 13 protein-coding genes (PCGs), and noncoding regions, all of which were identical to those of other euphausiid species. The most common start codon for the 13 PCGs was ATG, and the most common termination codon was TAA. The overall G + C content was 33.2% in the heavy strand. Euphausia crystallorophias was sister to E. superba in the phylogenetic analysis. The mitogenome of E. crystallorophias provided significant DNA molecular data for further identification and phylogenetic analysis within the euphausiids.

The complete mitochondrial genome of Trematomus loennbergii was studied using NGS technology with PacBio platform. The mitochondrial genome size was 19,374bp and it had 13 protein-coding genes, 22 tRNAs and 2 rRNAs. There were 4 types of stop codons which were TAA, TAG, AGG and T(AA) but start codon type was only one (ATG). The contents of GC were 44.09% and AT contents were 55.91%. To conduct phylogenetic analysis, 12 species in 3 families were used. The result suggested that T. loennbergii was close to Pagothenia borchgrevinki in Nototheniidae. This study would provide a fundamental data for molecular evolution of T. loennbergii.

The Macaroni penguin Eudyptes chrysolophus is a small crested penguin. In this study, the complete mitochondrial genome of E. chrysolophus is revealed for the first time. The mitogenome sequence is circular and 17,059 bp in length. It contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes similar to other Spheniscidae species. The total nucleotide composition is 30.53% (A), 32.86% (C), 13.96% (G), and 22.66% (T), and 46.81% for overall GC contents. The phylogenetic analysis shows a close relationship between E. chrysolophus and E. schlegeli. Our findings would be useful for further studies on phylogenetics and evolutionary history of the genus Eudyptes.

The complete mitochondrial genome of Macrourus witsoni was determined in this study by the Long-read Technology, such as PacBio Sequel System. The Long-read Technology, which can sequence continuously the whole vertebrate mitochondrial genome, allows more accurate genomes to be completed. The circular form of its mitochondrial genome was 16,714bp, which contained 13 protein-coding genes, 22 tRNA, and 2 rRNA. The gene orders of M.witsoni was identical to that of the other species of Macrouridae family. Phylogenetic analysis indicated M. witsoni was mostly close to C.kishinouyei in the Macrouridae family.

The complete mitochondrial genome of Notothenia rossii was obtained using PacBio Sequel long-read sequencing platform. The mitogenome of N. rossii was circular form and 18,274 bp long, which consists of 13 protein-coding genes, 24 tRNAs, 2 rRNAs, and non-coding control region. Particularly, we found duplicated tRNAThr and tRNAPro in addition to the typical 22 tRNAs. The phylogenetic tree revealed that N. rossii was most closely related to N. coriiceps among species in the Nototheniidae clade within the suborder Notothenioidei.

The full-length mitochondrial genome of Muraenolepis orangiensis (Vaillant, 1888) was studied using PacBio platform and it is first report in a Muraenolepididae family. The circular form of mitochondria genome is 16,833 bp including 13 protein-coding genes, two rRNA, and 22 tRNA. Start codon of 13 protein-coding genes was only ATG but three types of stop codons (TAA, T(AA), and TAG) were detected. To evaluate evolutionary position of M. orangiensis, the phylogenetic tree with other 13 Antarctic fishes belonged to five families were showed that M. orangiensis is unique cluster as a Muraenolepididae family and this study would provide fundamental data to understand the evolutionary relationship of fishes founded in Antarctic area.

The snow petrel, Pagodroma nivea is a small sea bird endemic to Antarctica and the Southern Ocean. Herein, we assembled a complete mitochondrial genome of the snow petrel as a first revealed genetic resource in Pagodroma family. The mitogenome is 17,279 bp in length and consists of 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. Base composition is 31.3% A, 25.3% T, 30.1% C, and 13.2% G with CG content of 43.4%. These results will provide a useful basis for further genetic and phylogenetic studies of this species.

The Weddell seal, Leptonychotes weddellii, which belongs to the family Phocidae, is an abundant pinniped that inhabits the Antarctica. Here, we present the complete mitochondrial genome and phylogeny of L. weddellii. The total length of the mitogenome is 16,762 bp, consisting of 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The base composition of the mitogenome is 34.26% (A), 25.51% (T), 27.09% (C), and 13.11% (G), and 40.22% for overall GC contents. The description of this mitogenome can provide information about variations at the intra-species level and aid phylogenetic studies in family Phocidae.

The complete mitochondrion DNA sequence of Lactarius lactarius was determined by next generation sequencing (NGS) platform as the first mitogenome report in the family. The mitogenome of L. lactarius wa 16,642 bp in length that contains 13 gene-encoded proteins, 2 ribosomal RNA gene (12S and 16S), 22 tRNA gene, and a control region (D-loop). Besides COX1 gene (GTG), all the other protein-coding genes showed typical (ATG) start codon. Incomplete stop condons (TA-/T–) were identified in COX2, COX3, ND2, ND3, ND4 and Cyt B. A phylogenetic analysis with currently reported mitogenomes of its relative species, L. lactarius formed a Lactariidae clade distinct from other families. Two species, Pentaceros japonicus (AB739063) and Banjos banjos (KT345965) were among the most closely related species with 86.61% and 86.33% sequence identity, respectively.

The complete mitochondrial genome of Pogonophryne albipinna was determined by the MiSeq platform, which was the first report in the family Artedidraconidae. The circular form of its mitochondrial genome was 17,086 bp, which contained the canonical eukaryotic 37 genes. The gene orders of P. albipinna was identical to the other icefish species, in which there was additional non-coding region and translocation of ND6 gene. Except for ATP6 gene and COI (GTG), 11 genes begin with the typical start codon, while incomplete stop codons (T– –) were identified in COII, ND4, and CytB. Phylogenetic tree with the currently known mitogenomes in suborder Notothenioidei showed that P. albipinna was located distinctly from those in Bathydraconidae and Nototheniidae forming a unique cluster as Artedidraconidae. The first complete mitochondrial genome of P. albipinna would be the fundamental data to understand the evolutional relationship of icefish species in the Antarctic Oceans.

The Cape petrel Daption capense, a seabird, is observed throughout the southern hemisphere including the Antarctic region. Herein, we report the complete mitogenome of Cape petrel with the GenBank accession number MH924023 to elucidate the genetic characteristics of this genus. The mitogenome is 17,312 bp long and comprises 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes. The overall base composition of the 13 PCGs is as follows: A (31.1%), C (30.3%), T (25.4%), and G (13.2%), with a GC content of 43.5%. The results provide useful information for further genetic studies in Procellariiformes.

The complete mitochondrial genome of Trematomus pennellii was determined by MiSeq platform. The mitogenome of T. pennellii was 15,976 bp in length and encoded 37 genes (13 proteins, 22 tRNAs, 2 ribosomal RNAs) and a non-coding control region (D-Loop). Overall A + T contents (54.10%) in the mitogenome was higher than G + C contents (45.90%). Twenty-nine genes were located on H strand, whereas eight genes were identified on L strand. Among 13 protein-coding genes, unusual start codons were identified in COX1 (GTG), ND6 (ATT), COX2 (ATC), and ATP6 (ATC). The incomplete stop codon (T–) was identified in six genes including COXII, COXIII, NAD2, NAD3, NAD4, and Cytb. The phylogenetic tree of complete genome indicated that Trematomus pennellii was most closely related to Trematomus bernacchii with 91.65% DNA sequence identity.