Inversion-driven mitochondrial gene rearrangements and their evolutionary implications in Littorinimorpha: insights from the Eunaticina papilla mitogenome.

To improve our understanding of the taxonomy and evolutionary relationships of Naticidae within the framework of Littorinimorpha, the complete mitochondrial genome of the Eunaticina papilla, was sequenced and analyzed using next generation sequencing (GenBank accession no. OR575181.1). The mitogenome is 16,415 bp in length and is comprised by the typical set of 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA genes (rRNAs), with a pronounced AT bias. Most tRNAs exhibit the typical cloverleaf secondary structure, whereas trnS2 and trnI lack the dihydrouridine (DHU) arm. Comparative analysis with ancestral gastropod gene order revealed extensive gene rearrangements in E. papilla, involving three gene clusters and encompassing 15 tRNA genes and 8 PCGs. Among these, inversion events were identified as the predominant rearrangement pattern, often accompanied by translocations. Phylogenetic analyses strongly support the monophyly of Littorinimorpha. E. papilla is placed in a well supported Naticidae clade and forms a sister group relationship with species of Polinices and Mammilla. Overall, this study uncovers inversion-driven mitochondrial gene rearrangements as a major evolutionary force in Littorinimorpha, expanding genomic resources for Naticidae and refining phylogenetic relationships within this diverse clade.