Abstract

After several revisions, Littorinimorpha has been classified as an order-level taxonomic unit under the subclass Heterobranchia of the class Gastropoda, but its suborder classification system remains controversial. In this study, high-throughput sequencing technology was used to obtain the complete mitochondrial genomes of three species from Stromboidea and Tonnoidea: Doxander vittatus, Tonna chinensis, and Phalium glaucum. Genome analysis revealed that the genomes of these three species are highly consistent in structure. They all contain 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes and lack a typical long non-coding control region. The phylogenetic tree constructed based on PCGs shows that Tonnoidea is a monophyletic group within Littorinimorpha, while Stromboidea is a paraphyletic group. Vermetoidea was identified as a separate evolutionary branch under this order. The present study clarifies the mitochondrial genomic characters of three species, D. vittatus, T. chinensis and P. glaucum and their positions in Littorinimorpha, which provides an important basis for evolutionary and phylogenetic studies of this order.

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