The Mitochondrial Genome of Littoraria melanostoma Reveals a Phylogenetic Relationship within Littorinimorpha

Abstract

Littoraria melanostoma (Gray, 1839) is one of the most common species of gastropods in mangroves. They quickly respond during the early stage of mangrove restoration and usually form a dominant community within a certain period. We characterized the complete mitochondrial genome of this species. The whole mitogenome of L. melanostoma was 16,149 bp in length and its nucleotide composition showed a high AT content of 64.16%. It had 37 genes, including 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, and 1 control region between tRNA-Phe and COX3. The A/T composition in the control region was 74.7%, and is much higher than the overall A/T composition of the mitochondrial genomes. The amino acid composition and codon usage of the mitochondrial genomes from seven superfamilies of Littorinimorpha were analyzed, and the results showed that CUU (Leu), GCU (Ala), AUU (Ile), UCU (Ser), UUA (Leu), GUU (Gly), and UUU (Phe) are the commonly used codons. The maximum likelihood phylogenetic tree reconstructed using 62 species of Littorinimorpha presented consistency between the molecular and morphological classifications, which provide a basis to understand the phylogeny and evolution of this order. In the phylogenetic tree, L. melanostoma is located within Littorinoidea and is closely related to L. sinensis, a rock-dwelling species that is widespread in the coastal intertidal zone of China.