Complete mitochondrial DNA sequence of the Eastern Asian catfish Silurus asotus (Siluriformes: Siluridae) from Lake Biwa in Japan.

The east Asian catfish Silurus asotus is a common species living in fresh water in Japan. The complete mitochondrial genome of the S. asotus from Lake Biwa in Japan was analyzed using next-generation sequencing. The mitochondrial genome of S. asotus was identified as a 16,515 bp circular molecule containing 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes, along with one A + T-rich control region. The AT content was 56.1%. Start codons ATG and GTG were found in 13 PCGs. Stop codons TAA, TAG, and AGA were observed in 13 PCGs. The heavy (H)-strand was predicted to have 12 PCGs and 14 tRNA and two rRNA genes, while the light (L)-strand was predicted to contain one PCGs and eight tRNA genes. The molecular phylogenetic analysis showed that S. asotus from Lake Biwa is genetically similar to S. asotus from China.

Complete mitochondrial DNA sequence of the Japanese endemic catfish Silurus biwaensis (Siluriformes: Siluridae) from Lake Biwa.

The Japanese endemic catfish Silurus biwaensis is distributed only in Lake Biwa and Yodo river drainages. There are four species of the genus Silurus in Japan, of which S. biwaensis has a most limited distribution. This catfish needs to be collected for DNA data owing to the lack of information related to its phylogenetic relationship. Here, the complete mitochondrial genome of the S. biwaensis from Lake Biwa in Japan was analyzed using next-generation sequencing. The mitochondrial genome of S. biwaensis was identified as a 16,531 bp circular molecule containing 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes, along with one A + T-rich control region. The AT content was 55.83%. The heavy (H)-strand was predicted to have 12 PCGs, 14 tRNA, and 2 rRNA genes, whereas the light (L)-strand was predicted to contain one PCG and eight tRNA genes. The start codons ATG, ATC, and GTG were found in 13 PCGs. The stop codons TAA, TAG, and AGA were observed in all PCGs, except CytB and COX3. All tRNA genes formed typical cloverleaf secondary structures. The molecular phylogenetic relationships estimated using 13 PCGs (maximum-likelihood method) indicated that S. biwaensis is genetically distinct from the sympatric species S. asotus and S. lithophilus. This result clearly indicated that S. biwaensis is a valid species.

Complete mitochondrial DNA sequence of the Japanese endemic catfish Silurus lithophilus (Siluriformes: Siluridae).

The Japanese endemic catfish Silurus lithophilus is distributed only in Lake Biwa, Lake Yogo, and their river drainages. There are four species of the genus Silurus in Japan, of which S. lithophilus has a limited distribution. This catfish needs to be collected for DNA data owing to the lack of information related to its conservation. Here, the complete mitochondrial genome of the S. lithophilus from Lake Biwa in Japan was analyzed using next-generation sequencing. The mitochondrial genome of S. lithophilus was identified as a 16,524 bp circular molecule containing 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes, along with one A + T-rich control region. The AT content was 55.89%. The heavy (H)-strand was predicted to have 12 PCGs and 15 tRNA, and 2 rRNA genes, whereas the light (L)-strand was predicted to contain one PCG and seven tRNA genes. The start codons ATG and GTG were found in 13 PCGs. The stop codons TAA, TAG, and AGA were observed in all PCGs, except CytB. All tRNA genes formed typical cloverleaf secondary structures. The molecular phylogenetic relationship, inferred using 13 PCGs (based on the maximum likelihood), was consistent with that reported in previous studies, which predicted a sister relationship between S. lithophilus and S. asotus. The results also clearly indicated that S. lithophilus is a valid species.

Complete mitochondrial DNA sequence of the East Asian minnow, Pungtungia herzi (Actinopterygii: Cypriniformes).

Some populations of the East Asian minnow Pungtungia herzi Herzenstein, 1892, which are naturally distributed in western Japan, have declined and are considered endangered. However, P. herzi has become a domestic invasive species in eastern Japan. Thus, knowledge of genetic features and phylogenetic relationships of P. herzi is important for conservation of this species and understanding its impact on ecosystems. We analyzed the complete mitochondrial genome using next generation sequencing of the East Asian minnow P. herzi from Yodo River, Osaka Prefecture, Japan. The mitochondrial genome of P. herzi consists of a circular molecule of 16,599 bp that includes 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one control region. The heavy (H)-strand was predicted to have 12 PCGs, 14 tRNA, and two rRNA genes, while the light (L)-strand was predicted to contain one PCGs and eight tRNA genes. The average AT content was 57.68%. The genes ATP8 and ATP6, ATP6 and COIII, ND4L and ND4, and ND5 and ND6 shared seven, one, seven, and four nucleotides, respectively. The initiation codons ATG and GTG were found in 12 and one genes, respectively. The termination codons TAA, TAG, incomplete TA-, and single T-- were observed in nine, one, one, and two genes, respectively. All the tRNA genes possessed a cloverleaf secondary structure. The phylogenetic relationships inferred using 13 PCGs (based on the maximum likelihood) were consistent with previous studies that predicted interrelationships of Cypriniformes.