Studies On Artificial Reproduction And The Complete Mitochondrial Genome Of Pseudobagrus Ussuriensis

Preliminary studies on artificial reproduction of Pseudobagrus ussuriensis were conducted in the present study. The proper hormone dosage for the female was PG0.5mg/kg+HCG300IU/kg+LRH-A210μg/kg in the first injection and PG5mg/kg+HCG1200IU/kg+LRH-A220μg/kg in the second injection. The effective time was12h at the water temperature of24℃～25.5.5days after hatching, the eggs yolk is absorbed completely and it can be fed with artificial food. In addition, we observed the postembryonic development of Pseudobagrus ussuriensis, selecting parent fish, artificial fertilization, hatch management, and other techniques were discussed in the paper.The complete mitochondrial genome was sequenced from the Ussuri catfish （Pseudobagrus ussuriensis）. The mitochondrial genome sequence is16,536bp in length and deposited in GenBank with accession number NC₀20344.1. It contains37genes （13protein-coding genes,22tRNA genes, and2rRNA genes） and2non-coding control regions. The light strand （L-strand） codes for1protein-coding gene （ND6） and8tRNAs （Gln, Ala, Asn, Cys, Tyr, Ser, Glu and Pro）, most of the genes are coded in the heavy strand （H-strand）（12protein-coding genes,14tRNA genes and2tRNA genes）. The nucleotide composition of Pseudobagrus ussuriensis is A31.8%, T26.8%, G14.9%, C26.5%, showing high average A%+T%and low G%contents as in most other vertebrates.Gene overlaps were found at9gene junctions and involved a total of30bp. In addition, a total of62bp intergenic spacer regions was present in10locations, ranging from1-32bp. The largest intergenic spacer region was located between tRNAAsn and tRNACys. Except for COX I gene using GTG as the initiation codon, all other12PCGs of the mtDNA started with the typical ATG codon.9PCGs used usual termination codons TAG （NDI, ND2and ND3） and TAA （COXI, ATP8, ATP6, ND4I, ND5and ND6）. The incomplete termination codon （T） was used for COX â…¡, COX III, ND4and Cytb. Transfer RNA （tRNA） genes ranged in length from67to75bp. The secondary structures of22tRNAs were predicted, and they all formed cloverleaf. The origin of the light strand replication （OL） was34bp in length, and was located between tRNAAsn and tRNACys. Analysis of the light strand replication of ten species in Bagridae, the seeondary structure of OL consisted of a conserve stem （CTTYCCCCGCCT/GAARGGGGCGGA） and loop structure. The mitochondrial DNA control region （CR） of Pseudobagrus ussuriensis was892bp, flanked by tRNAPro and tRNAPhe genes. The CR could be subdivided into three domains: termination associated sequences domain （TAS）, central conserved domain （CD） and conserved sequence block （CSB）.To further investigate the phylogenetic relationships of Bagridae, the phylogenetic analysis of14species in Siluriformes was conducted with Neighbor-Joining method based on nucleotide sequence of12protein-coding genes （except ND6gene）. The result support that Hemibagrus and Pseudobagrus are the only valid genera of East Asian bagrids.