Mitochondrial Genome Of Larva Of The Qinling Mountains And Its Parasitic Third-generation Worms

Gyrodactylids (Platyhelminthes:Monogenea) are widespread parasites of fishes, typically inhabiting the skin and gills of their hosts. Gyrodactylids have rapid population growth on host due to the particular life cycle. Are the pathogenic species, which can cause severe economic losses. In this study, mitochondrial genome of Gyrodactylus sp.l, Gyrodactylus sp.2 and Gyrodactylus sp.3 infect wild inhabiting streams in the south of Qinling Mountains. were determined and described. A comparative analyses of mitochondrial genome in Gyrodactylus and Paragyrodactylus variegatus were performed.Combine with 36 species 18S rDNA of Gyrodactylidae deposite in GeneBank database and 5 new 18S rDNA by this study. The phylogenetic relationships were reconstructed by using the phylogeny mothod, and phylogenetic relationships of Gyrodactylidae were preliminary analysis. The results were showed as follow:1. The mitochondrial genome length of Rhynchocypris lagowskii are 16606 bp, All sequence of the mitochondrial genome contain 13 protein genes,22 tRNA genes,2 rRNA gene.2. The mitochondrial genome length of Gyrodactylus sp.1, Gyrodactylus sp.2 and Gyrodactylus sp.3 are 14778 bp,14852 bp and 14772 bp, respectively. All sequence of the mitochondrial genome contain 12 protein genes,22 tRNA genes,2 rRNA gene and two major non-coding region (NCR), and all genes from same chain.3. The tRNA gene order between Gyrodactylus sp.2 and Gyrodactylus is different: the rearrangement of tRNAGln and tRNAMet. tRNAGln, tRNAPhe, tRNAMet of Gyrodactylus sp.2 between ND4 and NCR1. tRNATyr, tRNALeul, tRNASer2, tRNALeu2 and tRNAArg neighbor ND6 and ND5. However,only tRNAPhe of Gyrodactylus between ND4 and NCR1, and tRNATyr, tRNALeul, tRNAGIn, tRNAMet, tRNASer2, tRNALeu2, tRNAArg among ND6and ND5.4. The mitochondrial genome of Gyrodactylus sp.1, Gyrodactylus sp.2 and Gyrodactylus sp.3 have obvious bais with AT, and the A+T content of mitochondrial genome are 69.2%,70.8% and 71.6%, respectively. The A+T content value of species in this study is higher than that of all resporter mitochondrial genome of Gyrodactylus.5. Only start codon ATG was found in PCGs of Gyrodactylus sp.1 and Gyrodactylus sp.3 mitochondrial genomes, and the stop codon TAA was used in all PCGs except for ND1,which terminate with TAG. The two start condon ATG and TTG were employed for Gyrodactylus sp.2, all PCGs begin with the star codon ATG, while ND1 and CO? use the codon TTG. TAA is the typical stop codon, except for ND4 and ND1, which terminate with TAG.6. Except for tRNACYs, tRNASerl and tRNASer2 which absence DHU stem, All the 22 tRNA genes can be folded into the common cloverleaf structure.There are some unmatched base pair in tRNA secondary structure, and the main unmatch base pair was U-G. In Gyrodactylus mitochondrial genomes, tRNAIle, tRNAPr0 and tRNAHis have the high levels of nucleotide conservation.7. The mitochondrial genome of Gyrodactylus contain two almost identical NCR, NCR1 between tRNAPhe and ATP6, NCR2 between tRNAMet and tRNASer2, but the mitochondrial genome of Gyrodactylus sp.2 contain two different NCR. The NCR1 between in tRNAGln and tRNAPhe and the NCR2 is between in tRNAMet and ATP6, only two tRNA gene interval between the two major non-coding region. In NCR2 found repeat sequence, this mitochondrial genome structures showed Gyrodactylus sp.2 with the closely relationship among Paragyrodactylus variegatus.8. Phylogenetic relationship of Gyrodactylidae were reconstructed using the m aximum likelihood method (ML) and Bayesian inference method development (BI) base on the 18S rDNA sequences. Gyrodactylus sp.1-a and Gyrodactylus sp.l-b showed the sister relationship, and closed to Gyrodactylus sp.3. In another clade, Paragyrodactylus variegateswas located on the basal branch, Gyrodactylussp.2-a and Gyrodactylus sp.2-b forming a sister group, and closed to other Gyrodactylus spp. with 800 bp ITS sequences ofthe genus. We speculate that the short ITS Gyrodactylus species and Paragyrodactylus variegatus showed the closely relationship.