Institute of Evolution & Marine Biodiversity (IEMB), Ocean University of China, Qingdao, 266003, China.
Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China.
Sci Rep. 2019 Nov 27;9(1):17683. doi: 10.1038/s41598-019-54141-x.
The complete mitochondrial genomes of Harpago chiragra and Lambis lambis (Strombidae) were determined with the size of 15,460 bp and 15,481 bp, respectively, and both sequences contained 13 protein-coding genes, 22 tRNAs, and two rRNAs. H. chiragra and L. lambis have similar mitochondrial features, corresponding to typical gastropod mitochondrial genomes, such as the conserved gene order, a high A + T content (66.22% for H. chiragra and 66.10% for L. lambis), and preference for A + T-rich codons. The start or termination codon of same protein-coding gene in H. chiragra was consistent with that in L. lambis, except for the termination codon of cox1 gene (TAG for H. chiragra and TAA for L. lambis) and the start codon of nad4 (GTG for H. chiragra and ATG for L. lambis). Pairwise sequence alignments detected different degrees of variations in H. chiragra and L. lambis mitochondrial genomes; and the two species had lower levels of genetic distance (0.202 for nucleotide sequence) and closest relationships as compared to Strombus gigas and Oncomelania hupensis. The 13 partitioned nucleotide sequences of protein coding genes of H. chiragra and L. lambis were aligned with representatives of the main lineages of gastropods and their phylogenetic relationships were inferred. H. chiragra and L. lambis share the same gene order as Littorinimorpha species, except Vermetoidea, which demonstrate a gene rearrangement in species. The reconstructed phylogeny supports three major clades within Littorinimorpha: 1) Stromboidea, Tonnoidea, Littorinoidea, and Naticoidea, 2) Rissooidea and Truncatelloidea, and 3) Vermetoidea. In addition, a relaxed molecular clock calibrated with fossils dated the diversification of Strombidae near 112 (44-206) Mya and a possible radiation is detected to occur between 45-75 Mya, providing implications to understand the Cenozoic replacement event (65-135 Mya) of Aporrhaidae by Strombidae.
锯齿哈氏蜑螺和 Lambis lambis（宝贝科）的完整线粒体基因组大小分别为 15,460bp 和 15,481bp，均包含 13 个蛋白编码基因、22 个 tRNA 和两个 rRNA。H. chiragra 和 L. lambis 具有相似的线粒体特征，对应于典型的腹足纲线粒体基因组，如保守的基因排列、高 A+T 含量（H. chiragra 为 66.22%，L. lambis 为 66.10%）和偏好 A+T 丰富的密码子。H. chiragra 中相同蛋白编码基因的起始或终止密码子与 L. lambis 中的一致，除了 cox1 基因的终止密码子（H. chiragra 为 TAG，L. lambis 为 TAA）和 nad4 基因的起始密码子（H. chiragra 为 GTG，L. lambis 为 ATG）。成对序列比对检测到 H. chiragra 和 L. lambis 线粒体基因组存在不同程度的变异；与 Strombus gigas 和 Oncomelania hupensis 相比，这两个物种的遗传距离（核苷酸序列为 0.202）和亲缘关系最低。H. chiragra 和 L. lambis 的 13 个蛋白编码基因的核苷酸序列分区与腹足纲主要支系的代表进行了比对，并推断了它们的系统发育关系。H. chiragra 和 L. lambis 与 Littorinimorpha 物种共享相同的基因排列，除了 Vermetoidea 外，这表明物种中存在基因重排。重建的系统发育树支持 Littorinimorpha 内的三个主要分支：1）Stromboidea、Tonnoidea、Littorinoidea 和 Naticoidea，2）Rissooidea 和 Truncatelloidea，以及 3）Vermetoidea。此外，利用化石校准的松弛分子钟将 Strombidae 的多样化时间定在 112（44-206）Mya 附近，并且检测到可能的辐射发生在 45-75 Mya 之间，这为理解新生代（65-135 Mya）Aporrhaidae 被 Strombidae 取代的事件提供了启示。
