| In this study, the mitogenome of Haliotis discus hannai Ino、H. iris Martyn and their hybrid F1 were successfully sequenced. The structure of mitogenome in Haliotidae was so similar. Among them, hybrid Fi exhibited highly nucleotide homologies with H. discus hannai, suggesting hybrid Fi had the characteristics of maternal inheritance. We explored Gastropoda mitochondrial rearrangements by summing the features of Gastropoda mitogenome arrangement, and found its phylogenetic relationships with Gastropoda. Neighbor-joining tree based on protein-coding genes was reconstructed in order to study the classification of Gastropoda, and made some recommendations in this study.1. The mitogenome of H. discus hannai Ino、H. iris Martyn and their hybrid Fi were successfully sequenced using high-throughput sequencing technology, and increased three mitochondrial sequences in GenBank. The complete mitochondrial genome of the three abalones H. discus hannai Ino、H. iris Martyn and their hybrid F1 were 16,716 bp,17,131 bp and 16,719 bp in size, respectively, and included 37 typical mitochondrial genes. We didn’t find the gene deletion or addition phenomenons existing in Bivalvia, and the gene structure consistented with the determined Haliotidae species. Base composion of full sequence and protein-coding genes had a A+T bias, tRNA secondary structure had deletion and instability phenomenon, this proved that the mitochondrial structure and composition of species in Haliotidae were highly conserved. In sequence similarity, H. iris Martyn had a lower similarity with other abalones, an average of less than 85%, indicated that H. iris Martyn had a distantly related with others. The base composition and sequence homology of hybrid F1 was highest similar to H. discus hannai Ino, up to 99.4%, indicated that hybrid F1 mtDNA was maternally inherited. But we didn’t amplify the complete control region of H. discus hannai Ino、H. iris Martyn and their hybrid Fi successfully. In H. iris we had found 6 tracts of AT tandemly repeated unit, there were differences on the number and location of H. rubra Leach AT tandem repeat region, might provide new molecular markers for the identification of species between Haliotidae.2. We compared and analyzed the Gastropoda mitochondrial gene arrangement available in GenBank, using the base sequence of 13 protein-coding genes to rebuild the phylogeny of Gastropoda, revealing that Patellogastropoda、 Vetigastropoda、 Caenogastropa and Heterobrachia these four classification unit clustered four monophyletic clades, respectively, consistented with the current new classification of Gastropoda proposed by Bouchet and Rocroi. However, there was a deviation in the four branches, such as the Vermetoidea of Caenogastropa, it was significant different from other species of Caenogastropa in gene arrangement, and clustered a single group in the phylogenetic tree. We suggested that it cuold be raised to the same level with Littorinimorpha. Stylommatophora of Eupulmonata also clustered a single group. Results could be inferred from this study that Stylommatophora differentiated in an earlier time compared to Pulmonata other species. So Stylommatophora should be separated from Pulmonata alone, composing of a taxon as the same level as Pulmonata. Cocculiniformia and Neritimorpha mitogenome had not been sequenced currently, and Patellogastropoda only had one complete mitochondrial DNA sequence for now, so we need to strengthen sequencing the three branches’mitochondrial genome, to improve gastropod phylogeny and provide more reliable data in comprehensive study gastropod classification in the future. |
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