The complete mitochondrial genome of the Korean endemic species Cobitis hankugensis (Kim, Park, Son & Nalbant, 2003).

As one of efforts to conserve a genetic resource of the endemic cobitid species in the Korean peninsula, the complete mitogenome of Cobitis hankugensis (Kim, Park, Son & Nalbant, 2003) was determined using Illumina MiSeq system. The circular mitogenome was 16,557 bp length and encoded 13 protein-coding genes (PCGs), two ribosomal RNA genes, 22 tRNA genes, and a control region. Only the COX1 gene was identified with an aberrant initiation codon GTG, and an incomplete termination codon (T-/TA-) was identified in six PCGs including COX2, COX3, ND2, ND3, ND4, and Cytb genes. Phylogenetic analysis using 30 mitochondrial genomes belonging to Cobitidae, Botiidae, and Gyrinocheilidae showed that the highest identity (92.38%) with Kichulchoia brevifasciata (NC_027166). The complete mitogenome of C. hankugensis, an endemic species in Korea, will provide fundamental data on the evolutionary relationship of Cobitidae species.

Sequencing and annotation of the complete mitochondrial genome of a threatened labeonine fish, Cirrhinus reba.

The mitochondrial genome of a species is an essential resource for its effective conservation and phylogenetic studies. In this article, we present sequencing and characterization of the complete mitochondrial genome of a threatened labeonine fish, Cirrhinus reba collected from Khulna region of Bangladesh. The complete mitochondrial genome was 16,597 bp in size, which formed a circular double-stranded DNA molecule containing a total of 37 mitochondrial genes (13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes) with two non-coding regions, an origin of light strand replication (OL) and a displacement loop (D-loop), similar structure with other fishes of Teleostei. The phylogenetic tree demonstrated its close relationship with labeonine fishes. The complete mitogenome of Cirrhinus reba (GenBank no. MN862482) showed 99.96% identity to another haplotype of Cirrhinus reba (AP013325), followed by 90.18% identity with Labeo bata (AP011198).

Assessment of fish biodiversity in four Korean rivers using environmental DNA metabarcoding.

Environmental DNA (eDNA) metabarcoding is a cost-effective novel approach to estimate biodiversity in an ecosystem. In this study, the MiFish pipeline was employed to test if the system methodology is sufficiently reliable to estimate fish biodiversity in Korean rivers. A total of 125 unique haplotypes and 73 species were identified at the species level from 16 water samples collected from a single survey in four Korean rivers (Hyeongsan, Taehwa, Seomjin, and Nakdong). Among the four rivers, the highest species richness was recorded in the Seomjin River (52 species), followed by the Taehwa (42 species) and Hyeongsan (40 species) rivers. The Nakdong River (26 species) presented the lowest species richness and number of endemic species, presumably due to its metropolitan location and anthropogenic impacts, such as dams or weirs. We were also able to detect that five exotic species (Carassius cuvieri, Cyprinus carpio, Cyprinus megalophthalmus, Lepomis macrochirus, and Micropterus salmoides) are widely distributed in all surveyed rivers, a situation that might be problematic in terms of conservation. Our findings indicate that the eDNA metabarcoding technique is one of the most cost-effective scientific tools available for the management and conservation of the freshwater fish resources available in Korea. However, the low number of 12S sequences of endemic species in the database and low resolution of the MiFish region for differentiating several taxa should be upgraded for their wide use.

Complete mitochondrial genome of green shrimp, Chlorotocus crassicornis (Crustacea: Decapoda: Pandalidae) in Korean water.

The complete mitochondrial genome of green shrimp, Chlorotocus crassicornis (Costa, 1871) was generated by the combination of next-generation sequencing platform and long PCR technique. The mitochondrial genome of C. crassicornis was 16,500 bp, in which 13 protein-coding genes, two ribosomal RNAs, 22 transfer RNAs, and a putative control region was encoded. Based on the 13 protein-coding genes region, the phylogenetic tree was clearly demonstrated that C. crassicornis is closest to Pandalopsis japonica and Pandalus borealis with 77% identity. This mitogenome information will be helpful for the further studies of deep-sea fisheries resources management strategies in Korea including C. crassicornis species.

Characterization of the complete mitochondrial genome of Gangetic ailia, Ailia coila (Siluriformes: Ailiidae).

The first complete mitochondrial genome sequence of Ailia coila from Bangladesh was determined by the bioinformatic assembly of the next generation sequencing (NGS) reads. The constructed circular mitogenome for A. coila was 16,565 bp in length which harbored the canonical 13 protein-coding genes, 22 tRNAs, 2 rRNAs. Two non-coding regions, control region, D-loop (927 bp), and origin of light strand replication, OL (30 bp) were also well conserved in the mitogenome. Among the currently reported mitochondrial genomes in the order Siluriformes, A. coila was most closely related to Eutropiichthys vacha (AB919123) with 85.63% sequence identity.

Characterization of the complete mitochondrial genome of Silurus soldatovi in Korean river.

The complete mitochondrial genome of Silurus soldatovi firstly collected from a native Korean river was determined by the bioinformatics assembly of the next-generation sequencing (NGS) reads. The circular mitogenome was 16,525 bp in length which harbored canonical 13 protein-coding genes, 22 tRNAs, and 2 rRNAs, which was identical to those of family Siluridae. Twenty-eight genes were located on H strand, whereas the remaining nine genes were on L strand. Except for COX1 gene (GTG), other 12 protein-coding genes were predicted typical start codons (ATG). Among the currently known mitogenome sequences, S. soldatovi showed highest identity (99.38%) to the Chinese haplotype of S. soldatovi (NC022723) followed by the Chinese haplotype of Silurus asotus (JX087351). Interestingly, intraspecies variations of S. asotus are higher than those of interspecies and further study should be made to elucidate the evolutional relationship between two Silurus species.

Characterization of the complete mitochondrial genome of Odontobutis platycephala collected from Nakdong River, South Korea.

The complete mitochondrial genome of Odontobutis platycephala collected from a native Korean river was determined by the bioinformatics assembly of the next-generation sequencing (NGS) reads. The circular mitogenome was 17,590 bp length which harbored canonical 13 protein-coding genes, 22 tRNAs, and 2 rRNAs, which was identical to those of family Odontobutidae. Twenty-eight genes were located on H strand, whereas remaining nine genes were on L strand. Except for COX1 gene (GTG), other 12 protein-coding genes were predicted typical start codons (ATG). Among the currently known mitogenome sequences, O. platycephala showed highest identity (96.98%) to Korean haplotype of O. platycephala (NC010199).

Characterization of the complete mitochondrial genome of Chionobathyscus dewitti (Perciformes, Channichthyidae).

The complete mitochondrial genome sequence of the Icefish, Chionobathyscus dewitti was determined by the Next Generation Sequencing (NGS) analysis. The complete mitogenome was 17,452 bp in length, which encoded the canonical 13 protein-coding genes, 22 tRNAs, two rRNAs, and two non-coding regions. As shown in the other notothenids, translocation of ND6 and an additional non-coding region were identified, which is different from the typical vertebrate mitochondrial genomes. The C. dewitti was clustered distinctly from the those in the Chinodraco and Chaenocephalus, which supported the idea that this species should be classified in the different genus, Chionobathyscus in the family Channichthyidae.

Characterization of complete mitochondrial genome of Pogonophryne albipinna (Perciformes: Artedidraconidae).

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.

Molecular characterization of an adiponectin receptor homolog in the white leg shrimp, Litopenaeus vannamei.

Adiponectin (AdipoQ) and its receptors (AdipoRs) are strongly related to growth and development of skeletal muscle, as well as glucose and lipid metabolism in vertebrates. Herein we report the identification of the first full-length cDNA encoding an AdipoR homolog (Liv-AdipoR) from the decapod crustacean Litopenaeus vannamei using a combination of next generation sequencing (NGS) technology and bioinformatics analysis. The full-length Liv-AdipoR (1,245 bp) encoded a protein that exhibited the canonical seven transmembrane domains (7TMs) and the inversed topology that characterize members of the progestin and adipoQ receptor (PAQR) family. Based on the obtained sequence information, only a single orthologous AdipoR gene appears to exist in arthropods, whereas two paralogs, AdipoR1 and AdipoR2, have evolved in vertebrates. Transcriptional analysis suggested that the single Liv-AdipoR gene appears to serve the functions of two mammalian AdipoRs. At 72 h after injection of 50 pmol Liv-AdipoR dsRNA (340 bp) into L. vannamei thoracic muscle and deep abdominal muscle, transcription levels of Liv-AdipoR decreased by 93% and 97%, respectively. This confirmed optimal conditions for RNAi of Liv-AdipoR. Knockdown of Liv-AdipoR resulted in significant changes in the plasma levels of ammonia, 3-methylhistine, and ornithine, but not plasma glucose, suggesting that that Liv-AdipoR is important for maintaining muscle fibers. The chronic effect of Liv-AdipoR dsRNA injection was increased mortality. Transcriptomic analysis showed that 804 contigs were upregulated and 212 contigs were downregulated by the knockdown of Liv-AdipoR in deep abdominal muscle. The significantly upregulated genes were categorized as four main functional groups: RNA-editing and transcriptional regulators, molecular chaperones, metabolic regulators, and channel proteins.