Artemia is an industrially important genus used in aquaculture as a nutritious diet for fish and as an aquatic model organism for toxicity tests. However, despite the significance of Artemia, genomic research remains incomplete and knowledge on its genomic characteristics is insufficient. In particular, A. franciscana of North America has been widely used in fisheries of other continents, resulting in invasion to native species. Therefore, studies on population genetics and molecular marker development as well as morphological analyses are required to investigate its population structure and to discriminate closely related species. Here, we used the Illumina Hi-Seq platform to estimate the genomic characteristics of A. franciscana through genome survey sequencing. Further, simple sequence repeat (SSR) loci were identified for microsatellite marker development. The predicted genome size was ~867 Mb using K-mer analysis (K=17), and heterozygosity and duplication rates were 0.655% and 0.809%, respectively. A total of 421,467 SSRs were identified from the genome survey assembly, most of which were dinucleotide motifs with a frequency of 77.22%. This study will be a useful basis in genomic and genetic research for A. franciscana.

The genus Pogonophryne is a speciose group that includes 28 species inhabiting the coastal or deep waters of the Antarctic Southern Ocean. The genus has been divided into five species groups, among which the P. albipinna group is the most deep-living group and is characterized by a lack of spots on the top of the head. Here, we carried out genome survey sequencing of P. albipinna using the Illumina HiSeq platform to estimate the genomic characteristics and identify genome-wide microsatellite motifs. The genome size was predicted to be ~883.8 Mb by K-mer analysis (K=25), and the heterozygosity and repeat ratio were 0.289% and 39.03%, respectively. The genome sequences were assembled into 571,624 contigs, covering a total length of ~819.3 Mb with an N50 of 2,867 bp. A total of 2,217,422 simple sequence repeat motifs were identified from the assembly data, and the number of repeats decreased as the length and number of repeats increased. These data will provide a useful foundation for the development of new molecular markers for the P. albipinna group as well as for further whole genome sequencing of P. albipinna.

The Antarctic toothfish, Dissostichus mawsoni , belongs to the Nototheniidae family and is distributed in sub-zero temperatures below S60° latitude in the Southern Ocean. Therefore, it is an attractive model species to study the stenothermal cold-adapted character state. In this study, we successfully generated highly contiguous genome sequences of D. mawsoni , which contained 1 062 scaffolds with a N50 length of 36.98 Mb and longest scaffold length of 46.82 Mb. Repetitive elements accounted for 40.87% of the genome. We also inferred 32 914 protein-coding genes using in silico gene prediction and transcriptome sequencing and detected splicing variants using Isoform-Sequencing (Iso-Seq), which will be invaluable resource for further exploration of the adaptation mechanisms of Antarctic toothfish. This new high-quality reference genome of D. mawsoni provides a fundamental resource for a deeper understanding of cold adaptation and conservation of species.

Trematomus species (suborder Notothenioidei; family Nototheniidae) are widely distributed in the southern oceans near Antarctica. There are 11 recognized species in the genus Trematomus, and notothenioids are known to have high chromosomal diversity (2n = 24–58) because of relatively recent and rapid adaptive radiation. Herein, we report the chromosomal-level genome assembly of T. loennbergii, the first characterized genome representative of the genus Trematomus. The final genome assembly of T. loennbergii was obtained using a Pacific Biosciences long-read sequencing platform and high-throughput chromosome conformation capture technology. Twenty-three chromosomal-level scaffolds were assembled to 940 Mb in total size, with a longest contig size of 48.5 Mb and contig N50 length of 24.7 Mb. The genome contained 42.03% repeat sequences, and a total of 24,525 protein-coding genes were annotated. We produced a high-quality genome assembly of T. loennbergii. Our results provide a first reference genome for the genus Trematomus and will serve as a basis for studying the molecular taxonomy and evolution of Antarctic fish.

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.