A comprehensive description and evolutionary analysis of 9 Loliginidae mitochondrial genomes

Abstract

The family Loliginidae is a diverse and economically valuable group of cephalopods. To investigate the evolution of their mitochondrial genomes, we characterized and compared these genomes among nine species, six newly sequenced. In all nine species, mitochondrial genomes followed the typical invertebrate canonical organization with 13 protein-coding genes, 22 tRNAs, and two rRNAs. However, different from the vertebrates, there were three non-coding control regions for most of the loliginid species. As for the gene arrangement and organization, the mitochondrial genome of Sepioteuthis lessoniana is totally different from the other eight species—there is only one control region, but 25 tRNAs. We analyzed the level of selective pressures imposed on different protein-coding genes, and found that stabilizing selection is strongest on cytb. We then tested the phylogenetic utility of this new mitochondrial genome data using 13 protein-coding genes and the results showed that Loliginidae is divided into two major lineages, with S. lessoniana sister to a clade comprising the remaining species. Loliolus beka, Loliolus japonica, Loliolus uyii, Uroteuthis chinensis, Uroteuthis edulis, Uroteuthis duvauceli, Heterololigo bleekeri, and Doryteuthis opalescens were recovered as a monophyletic group.