Comparative mitogenomic analyses of the infraclass Pteriomorphia (Mollusca: Bivalvia) provides novel insights into gene rearrangement and phylogeny

Abstract

The infraclass Pteriomorphia within the phylum Mollusca, class Bivalvia, encompasses a diverse group of bivalve mollusks characterized by their unique morphological and ecological traits. However, the molecular data of Pteriomorphia remains limited, constraining classification and phylogenetic analysis within the infraclass Pteriomorphia. In this study, we sequenced the mitogenomes of 15 pteriomorphians using high-throughput sequencing technology and conducted comparative genomic analysis with 58 sequences available on GenBank. The newly sequenced mitogenomes all exhibited a circular double-stranded structure, ranging in size from 12,844 to 28,105 bp. Mitogenome features, including nucleotide composition, codon usage, and amino acid content, exhibited significant deviations. The mitochondrial gene orders (MGOs) in pteriomorphians also exhibited significant diversity, with 44 distinct patterns identified (excluding the tRNA gene). The gene rearrangement analysis inferred that the ancestral MGO evolution pathway supported the hypothesis that the common ancestor MGO of Mytilida is the closest to that of the entire infraclass Pteriomorphia. The reconstructed phylogeny also indicated the order Mytilida as the basal group of Pteriomorphia. Furthermore, the analysis revealed that Ostreida and Pectinida were sister taxa, while Ostreoidea and the Pinnoidea were sister taxa within Ostreida. Gene rearrangement analysis further suggested that the MGOs of Arcida and Pectinida likely evolved from the ancestral MGO of Ostreida. Our study provided new insights into the phylogenetic relationships and evolution of gene rearrangements within the subclass Pteriomorphia.