A comprehensive study on the mitochondrial genome of Volva habei and exploring phylogenetic relationships in Littorinimorpha.

In order to enrich our taxonomic and systematic comprehension of Ovulidae within the evolutionary framework of Littorinimorpha. we present a comprehensive analysis of the mitochondrial genome (mitogenome) sequence of Volva habei using next-generation sequencing technology (GenBank accession number OR492307). The mitogenome spans a total length of 16,519 bp, encompassing a complete set of 37 genes, including 13 protein-coding genes (PCGs), 22 tRNAs and two rRNAs, demonstrating a distinct AT bias. Notably, trnS2 lacks a dihydrouracil (DHU) arm, thus preventing the formation of a typical secondary structure. In contrast, the remaining tRNAs exhibit a characteristic cloverleaf-like secondary structure. Comparative analysis with ancestral gastropods reveals substantial differences in three gene clusters (or genes), incorporating fifteen tRNAs and eight PCGs. Of particular significance are the observed inversions and translocations, representing the predominant types of rearrangements in V. habei. Phylogenetic analysis strongly supports the monophyletic grouping of all Littorinimorpha species, with V. habei forming a distinct Ovulidae clade. It is noteworthy that V. habei forms a sister group with Cypraeidae, collectively belonging to the Cypraeoidea. In summary, this study not only advances our comprehension of the entire mitochondrial dataset for Calyptraeoidea but also provides novel insights into the phylogenetic relationships within Littorinimorpha.